source: rtems/c/src/lib/libbsp/sparc/shared/can/grcan.c @ 9855690

/*
 *  GRCAN driver
 *
 *  COPYRIGHT (c) 2007.
 *  Cobham Gaisler AB.
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

#include <bsp.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>
#include <rtems/bspIo.h>

#include <bsp/grcan.h>
#include <drvmgr/drvmgr.h>
#include <drvmgr/ambapp_bus.h>
#include <ambapp.h>

#if (((__RTEMS_MAJOR__ << 16) | (__RTEMS_MINOR__ << 8) | __RTEMS_REVISION__) >= 0x040b63)

/* Spin locks mapped via rtems_interrupt_lock_* API: */
#define SPIN_DECLARE(lock) RTEMS_INTERRUPT_LOCK_MEMBER(lock)
#define SPIN_INIT(lock, name) rtems_interrupt_lock_initialize(lock, name)
#define SPIN_LOCK(lock, level) rtems_interrupt_lock_acquire_isr(lock, &level)
#define SPIN_LOCK_IRQ(lock, level) rtems_interrupt_lock_acquire(lock, &level)
#define SPIN_UNLOCK(lock, level) rtems_interrupt_lock_release_isr(lock, &level)
#define SPIN_UNLOCK_IRQ(lock, level) rtems_interrupt_lock_release(lock, &level)
#define SPIN_IRQFLAGS(k) rtems_interrupt_lock_context k
#define SPIN_ISR_IRQFLAGS(k) SPIN_IRQFLAGS(k)

#else

/* maintain compatibility with older versions of RTEMS: */
#define SPIN_DECLARE(name)
#define SPIN_INIT(lock, name)
#define SPIN_LOCK(lock, level)
#define SPIN_LOCK_IRQ(lock, level) rtems_interrupt_disable(level)
#define SPIN_UNLOCK(lock, level)
#define SPIN_UNLOCK_IRQ(lock, level) rtems_interrupt_enable(level)
#define SPIN_IRQFLAGS(k) rtems_interrupt_level k
#define SPIN_ISR_IRQFLAGS(k)

#endif

/* Maximum number of GRCAN devices supported by driver */
#define GRCAN_COUNT_MAX 8

#define WRAP_AROUND_TX_MSGS 1
#define WRAP_AROUND_RX_MSGS 2
#define GRCAN_MSG_SIZE sizeof(struct grcan_msg)
#define BLOCK_SIZE (16*4)

/* grcan needs to have it buffers aligned to 1k boundaries */
#define BUFFER_ALIGNMENT_NEEDS 1024

/* Default Maximium buffer size for statically allocated buffers */
#ifndef TX_BUF_SIZE
 #define TX_BUF_SIZE (BLOCK_SIZE*16)
#endif

/* Make receiver buffers bigger than transmitt */
#ifndef RX_BUF_SIZE
 #define RX_BUF_SIZE ((3*BLOCK_SIZE)*16)
#endif

#ifndef IRQ_CLEAR_PENDING
 #define IRQ_CLEAR_PENDING(irqno)
#endif

#ifndef IRQ_UNMASK
 #define IRQ_UNMASK(irqno)
#endif

#ifndef IRQ_MASK
 #define IRQ_MASK(irqno)
#endif

#ifndef GRCAN_DEFAULT_BAUD
 /* default to 500kbits/s */
 #define GRCAN_DEFAULT_BAUD 500000
#endif

#ifndef GRCAN_SAMPLING_POINT
 #define GRCAN_SAMPLING_POINT 80
#endif

/* Uncomment for debug output */
/****************** DEBUG Definitions ********************/
#define DBG_TX 2
#define DBG_RX 4
#define DBG_STATE 8

#define DEBUG_FLAGS (DBG_STATE | DBG_RX | DBG_TX )
/*
#define DEBUG
#define DEBUGFUNCS
*/
#include <bsp/debug_defs.h>

/*********************************************************/

int state2err[4] = {
        /* STATE_STOPPED */ GRCAN_RET_NOTSTARTED,
        /* STATE_STARTED */ GRCAN_RET_OK,
        /* STATE_BUSOFF  */ GRCAN_RET_BUSOFF,
        /* STATE_AHBERR  */ GRCAN_RET_AHBERR
};

struct grcan_msg {
        unsigned int head[2];
        unsigned char data[8];
};

struct grcan_config {
        struct grcan_timing timing;
        struct grcan_selection selection;
        int abort;
        int silent;
};

struct grcan_priv {
        struct drvmgr_dev *dev; /* Driver manager device */
        char devName[32];       /* Device Name */
        unsigned int baseaddr, ram_base;
        struct grcan_regs *regs;
        int irq;
        int minor;
        int open;
        int started;
        unsigned int channel;
        int flushing;
        unsigned int corefreq_hz;

        /* Circular DMA buffers */
        void *_rx, *_rx_hw;
        void *_tx, *_tx_hw;
        void *txbuf_adr;
        void *rxbuf_adr;
        struct grcan_msg *rx;
        struct grcan_msg *tx;
        unsigned int rxbuf_size;    /* requested RX buf size in bytes */
        unsigned int txbuf_size;    /* requested TX buf size in bytes */

        int txblock, rxblock;
        int txcomplete, rxcomplete;
        int txerror, rxerror;

        struct grcan_filter sfilter;
        struct grcan_filter afilter;
        int config_changed; /* 0=no changes, 1=changes ==> a Core reset is needed */
        struct grcan_config config;
        struct grcan_stats stats;

        rtems_id rx_sem, tx_sem, txempty_sem, dev_sem;
        SPIN_DECLARE(devlock);
};

static void __inline__ grcan_hw_reset(struct grcan_regs *regs);

static int grcan_hw_read_try(
        struct grcan_priv *pDev,
        struct grcan_regs *regs,
        CANMsg *buffer,
        int max);

static int grcan_hw_write_try(
        struct grcan_priv *pDev,
        struct grcan_regs *regs,
        CANMsg *buffer,
        int count);

static void grcan_hw_config(
        struct grcan_regs *regs,
        struct grcan_config *conf);

static void grcan_hw_accept(
        struct grcan_regs *regs,
        struct grcan_filter *afilter);

static void grcan_hw_sync(
        struct grcan_regs *regs,
        struct grcan_filter *sfilter);

static void grcan_interrupt(void *arg);

#ifdef GRCAN_REG_BYPASS_CACHE
#define READ_REG(address) _grcan_read_nocache((unsigned int)(address))
#else
#define READ_REG(address) (*(volatile unsigned int *)(address))
#endif

#ifdef GRCAN_DMA_BYPASS_CACHE
#define READ_DMA_WORD(address) _grcan_read_nocache((unsigned int)(address))
#define READ_DMA_BYTE(address) _grcan_read_nocache_byte((unsigned int)(address))
static unsigned char __inline__ _grcan_read_nocache_byte(unsigned int address)
{
        unsigned char tmp;
        __asm__ (" lduba [%1]1, %0 "
            : "=r"(tmp)
            : "r"(address)
        );
        return tmp;
}
#else
#define READ_DMA_WORD(address) (*(volatile unsigned int *)(address))
#define READ_DMA_BYTE(address) (*(volatile unsigned char *)(address))
#endif

#if defined(GRCAN_REG_BYPASS_CACHE) || defined(GRCAN_DMA_BYPASS_CACHE)
static unsigned int __inline__ _grcan_read_nocache(unsigned int address)
{
        unsigned int tmp;
        __asm__ (" lda [%1]1, %0 "
                : "=r"(tmp)
                : "r"(address)
        );
        return tmp;
}
#endif

#define NELEM(a) ((int) (sizeof (a) / sizeof (a[0])))

static int grcan_count = 0;
static struct grcan_priv *priv_tab[GRCAN_COUNT_MAX];

/******************* Driver manager interface ***********************/

/* Driver prototypes */
int grcan_device_init(struct grcan_priv *pDev);

int grcan_init2(struct drvmgr_dev *dev);
int grcan_init3(struct drvmgr_dev *dev);

struct drvmgr_drv_ops grcan_ops = 
{
        .init = {NULL, grcan_init2, grcan_init3, NULL},
        .remove = NULL,
        .info = NULL
};

struct amba_dev_id grcan_ids[] = 
{
        {VENDOR_GAISLER, GAISLER_GRCAN},
        {VENDOR_GAISLER, GAISLER_GRHCAN},
        {0, 0}          /* Mark end of table */
};

struct amba_drv_info grcan_drv_info =
{
        {
                DRVMGR_OBJ_DRV,                 /* Driver */
                NULL,                           /* Next driver */
                NULL,                           /* Device list */
                DRIVER_AMBAPP_GAISLER_GRCAN_ID, /* Driver ID */
                "GRCAN_DRV",                    /* Driver Name */
                DRVMGR_BUS_TYPE_AMBAPP,         /* Bus Type */
                &grcan_ops,
                NULL,                           /* Funcs */
                0,                              /* No devices yet */
                0,
        },
        &grcan_ids[0]
};

void grcan_register_drv (void)
{
        DBG("Registering GRCAN driver\n");
        drvmgr_drv_register(&grcan_drv_info.general);
}

int grcan_init2(struct drvmgr_dev *dev)
{
        struct grcan_priv *priv;

        DBG("GRCAN[%d] on bus %s\n", dev->minor_drv, dev->parent->dev->name);
        if (GRCAN_COUNT_MAX <= grcan_count)
                return DRVMGR_ENORES;
        priv = dev->priv = malloc(sizeof(struct grcan_priv));
        if ( !priv )
                return DRVMGR_NOMEM;
        memset(priv, 0, sizeof(*priv));
        priv->dev = dev;

        /* This core will not find other cores, so we wait for init2() */

        return DRVMGR_OK;
}

int grcan_init3(struct drvmgr_dev *dev)
{
        struct grcan_priv *priv;
        char prefix[32];

        priv = dev->priv;

        /*
         * Now we take care of device initialization.
         */

        if ( grcan_device_init(priv) ) {
                return DRVMGR_FAIL;
        }

        priv_tab[grcan_count] = priv;
        grcan_count++;

        /* Get Filesystem name prefix */
        prefix[0] = '\0';
        if ( drvmgr_get_dev_prefix(dev, prefix) ) {
                /* Failed to get prefix, make sure of a unique FS name
                 * by using the driver minor.
                 */
                sprintf(priv->devName, "grcan%d", dev->minor_drv);
        } else {
                /* Got special prefix, this means we have a bus prefix
                 * And we should use our "bus minor"
                 */
                sprintf(priv->devName, "%sgrcan%d", prefix, dev->minor_bus);
        }

        return DRVMGR_OK;
}

int grcan_device_init(struct grcan_priv *pDev)
{
        struct amba_dev_info *ambadev;
        struct ambapp_core *pnpinfo;

        /* Get device information from AMBA PnP information */
        ambadev = (struct amba_dev_info *)pDev->dev->businfo;
        if ( ambadev == NULL ) {
                return -1;
        }
        pnpinfo = &ambadev->info;
        pDev->irq = pnpinfo->irq;
        pDev->regs = (struct grcan_regs *)pnpinfo->apb_slv->start;
        pDev->minor = pDev->dev->minor_drv;

        /* Get frequency in Hz */
        if ( drvmgr_freq_get(pDev->dev, DEV_APB_SLV, &pDev->corefreq_hz) ) {
                return -1;
        }

        DBG("GRCAN frequency: %d Hz\n", pDev->corefreq_hz);

        /* Reset Hardware before attaching IRQ handler */
        grcan_hw_reset(pDev->regs);

        /* RX Semaphore created with count = 0 */
        if ( rtems_semaphore_create(rtems_build_name('G', 'C', 'R', '0' + pDev->minor),
                0,
                RTEMS_FIFO|RTEMS_SIMPLE_BINARY_SEMAPHORE|RTEMS_NO_INHERIT_PRIORITY|\
                RTEMS_LOCAL|RTEMS_NO_PRIORITY_CEILING, 
                0,
                &pDev->rx_sem) != RTEMS_SUCCESSFUL ) {
                return RTEMS_INTERNAL_ERROR;
        }

        /* TX Semaphore created with count = 0 */
        if ( rtems_semaphore_create(rtems_build_name('G', 'C', 'T', '0' + pDev->minor),
                0,
                RTEMS_FIFO|RTEMS_SIMPLE_BINARY_SEMAPHORE|RTEMS_NO_INHERIT_PRIORITY|\
                RTEMS_LOCAL|RTEMS_NO_PRIORITY_CEILING, 
                0,
                &pDev->tx_sem) != RTEMS_SUCCESSFUL ) {
                return RTEMS_INTERNAL_ERROR;
        }

        /* TX Empty Semaphore created with count = 0 */
        if ( rtems_semaphore_create(rtems_build_name('G', 'C', 'E', '0' + pDev->minor),
                0,
                RTEMS_FIFO|RTEMS_SIMPLE_BINARY_SEMAPHORE|RTEMS_NO_INHERIT_PRIORITY|\
                RTEMS_LOCAL|RTEMS_NO_PRIORITY_CEILING, 
                0,
                &pDev->txempty_sem) != RTEMS_SUCCESSFUL ) {
                return RTEMS_INTERNAL_ERROR;
        }

        /* Device Semaphore created with count = 1 */
        if ( rtems_semaphore_create(rtems_build_name('G', 'C', 'A', '0' + pDev->minor),
                1,
                RTEMS_FIFO|RTEMS_SIMPLE_BINARY_SEMAPHORE|RTEMS_NO_INHERIT_PRIORITY|\
                RTEMS_LOCAL|RTEMS_NO_PRIORITY_CEILING,
                0,
                &pDev->dev_sem) != RTEMS_SUCCESSFUL ) {
                return RTEMS_INTERNAL_ERROR;
        }

        return 0;
}

static void __inline__ grcan_hw_reset(struct grcan_regs *regs)
{
        regs->ctrl = GRCAN_CTRL_RESET;
}

static rtems_device_driver grcan_hw_start(struct grcan_priv *pDev)
{
        /*
         * tmp is set but never used. GCC gives a warning for this
         * and we need to tell GCC not to complain.
         */
        unsigned int tmp RTEMS_UNUSED;

        SPIN_IRQFLAGS(oldLevel);

        FUNCDBG();

        /* Check that memory has been allocated successfully */
        if (!pDev->tx || !pDev->rx)
                return RTEMS_NO_MEMORY;

        /* Configure FIFO configuration register
         * and Setup timing
         */
        if (pDev->config_changed) {
                grcan_hw_config(pDev->regs, &pDev->config);
                pDev->config_changed = 0;
        }

        /* Setup receiver */
        pDev->regs->rx0addr = (unsigned int)pDev->_rx_hw;
        pDev->regs->rx0size = pDev->rxbuf_size;

        /* Setup Transmitter */
        pDev->regs->tx0addr = (unsigned int)pDev->_tx_hw;
        pDev->regs->tx0size = pDev->txbuf_size;

        /* Setup acceptance filters */
        grcan_hw_accept(pDev->regs, &pDev->afilter);

        /* Sync filters */
        grcan_hw_sync(pDev->regs, &pDev->sfilter);

        /* Clear status bits */
        tmp = READ_REG(&pDev->regs->stat);
        pDev->regs->stat = 0;

        /* Setup IRQ handling */

        /* Clear all IRQs */
        tmp = READ_REG(&pDev->regs->pir);
        pDev->regs->picr = 0x1ffff;

        /* unmask TxLoss|TxErrCntr|RxErrCntr|TxAHBErr|RxAHBErr|OR|OFF|PASS */
        pDev->regs->imr = 0x1601f;

        /* Enable routing of the IRQs */
        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        IRQ_UNMASK(pDev->irq + GRCAN_IRQ_TXSYNC);
        IRQ_UNMASK(pDev->irq + GRCAN_IRQ_RXSYNC);
        IRQ_UNMASK(pDev->irq + GRCAN_IRQ_IRQ);
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        /* Reset some software data */
        /*pDev->txerror = 0;
           pDev->rxerror = 0; */

        /* Enable receiver/transmitter */
        pDev->regs->rx0ctrl = GRCAN_RXCTRL_ENABLE;
        pDev->regs->tx0ctrl = GRCAN_TXCTRL_ENABLE;

        /* Enable HurriCANe core */
        pDev->regs->ctrl = GRCAN_CTRL_ENABLE;

        /* Leave transmitter disabled, it is enabled when
         * trying to send something.
         */
        return RTEMS_SUCCESSFUL;
}

static void grcan_hw_stop(struct grcan_priv *pDev)
{
        FUNCDBG();

        /* Mask all IRQs */
        pDev->regs->imr = 0;
        IRQ_MASK(pDev->irq + GRCAN_IRQ_TXSYNC);
        IRQ_MASK(pDev->irq + GRCAN_IRQ_RXSYNC);
        IRQ_MASK(pDev->irq + GRCAN_IRQ_IRQ);

        /* Disable receiver & transmitter */
        pDev->regs->rx0ctrl = 0;
        pDev->regs->tx0ctrl = 0;
}

static void grcan_sw_stop(struct grcan_priv *pDev)
{
        /* Reset semaphores to the initial state and wakeing
         * all threads waiting for an IRQ. The threads that
         * get woken up must check for RTEMS_UNSATISFIED in
         * order to determine that they should return to
         * user space with error status.
         */
        rtems_semaphore_flush(pDev->rx_sem);
        rtems_semaphore_flush(pDev->tx_sem);
        rtems_semaphore_flush(pDev->txempty_sem);
}

static void grcan_hw_config(struct grcan_regs *regs, struct grcan_config *conf)
{
        unsigned int config = 0;

        /* Reset HurriCANe Core */
        regs->ctrl = 0;

        if (conf->silent)
                config |= GRCAN_CFG_SILENT;

        if (conf->abort)
                config |= GRCAN_CFG_ABORT;

        if (conf->selection.selection)
                config |= GRCAN_CFG_SELECTION;

        if (conf->selection.enable0)
                config |= GRCAN_CFG_ENABLE0;

        if (conf->selection.enable1)
                config |= GRCAN_CFG_ENABLE1;

        /* Timing */
        config |= (conf->timing.bpr << GRCAN_CFG_BPR_BIT) & GRCAN_CFG_BPR;
        config |= (conf->timing.rsj << GRCAN_CFG_RSJ_BIT) & GRCAN_CFG_RSJ;
        config |= (conf->timing.ps1 << GRCAN_CFG_PS1_BIT) & GRCAN_CFG_PS1;
        config |= (conf->timing.ps2 << GRCAN_CFG_PS2_BIT) & GRCAN_CFG_PS2;
        config |=
            (conf->timing.scaler << GRCAN_CFG_SCALER_BIT) & GRCAN_CFG_SCALER;

        /* Write configuration */
        regs->conf = config;

        /* Enable HurriCANe Core */
        regs->ctrl = GRCAN_CTRL_ENABLE;
}

static void grcan_hw_accept(
        struct grcan_regs *regs,
        struct grcan_filter *afilter
)
{
        /* Disable Sync mask totaly (if we change scode or smask
         * in an unfortunate way we may trigger a sync match)
         */
        regs->rx0mask = 0xffffffff;

        /* Set Sync Filter in a controlled way */
        regs->rx0code = afilter->code;
        regs->rx0mask = afilter->mask;
}

static void grcan_hw_sync(struct grcan_regs *regs, struct grcan_filter *sfilter)
{
        /* Disable Sync mask totaly (if we change scode or smask
         * in an unfortunate way we may trigger a sync match)
         */
        regs->smask = 0xffffffff;

        /* Set Sync Filter in a controlled way */
        regs->scode = sfilter->code;
        regs->smask = sfilter->mask;
}

static unsigned int grcan_hw_rxavail(
        unsigned int rp,
        unsigned int wp, unsigned int size
)
{
        if (rp == wp) {
                /* read pointer and write pointer is equal only
                 * when RX buffer is empty.
                 */
                return 0;
        }

        if (wp > rp) {
                return (wp - rp) / GRCAN_MSG_SIZE;
        } else {
                return (size - (rp - wp)) / GRCAN_MSG_SIZE;
        }
}

static unsigned int grcan_hw_txspace(
        unsigned int rp,
        unsigned int wp,
        unsigned int size
)
{
        unsigned int left;

        if (rp == wp) {
                /* read pointer and write pointer is equal only
                 * when TX buffer is empty.
                 */
                return size / GRCAN_MSG_SIZE - WRAP_AROUND_TX_MSGS;
        }

        /* size - 4 - abs(read-write) */
        if (wp > rp) {
                left = size - (wp - rp);
        } else {
                left = rp - wp;
        }

        return left / GRCAN_MSG_SIZE - WRAP_AROUND_TX_MSGS;
}

#define MIN_TSEG1 1
#define MIN_TSEG2 2
#define MAX_TSEG1 14
#define MAX_TSEG2 8

static int grcan_calc_timing(
        unsigned int baud,      /* The requested BAUD to calculate timing for */
        unsigned int core_hz,   /* Frequency in Hz of GRCAN Core */
        unsigned int sampl_pt,
        struct grcan_timing *timing     /* result is placed here */
)
{
        int best_error = 1000000000;
        int error;
        int best_tseg = 0, best_brp = 0, brp = 0;
        int tseg = 0, tseg1 = 0, tseg2 = 0;
        int sjw = 1;

        /* Default to 90% */
        if ((sampl_pt < 50) || (sampl_pt > 99)) {
                sampl_pt = GRCAN_SAMPLING_POINT;
        }

        if ((baud < 5000) || (baud > 1000000)) {
                /* invalid speed mode */
                return -1;
        }

        /* find best match, return -2 if no good reg
         * combination is available for this frequency
         */

        /* some heuristic specials */
        if (baud > ((1000000 + 500000) / 2))
                sampl_pt = 75;

        if (baud < ((12500 + 10000) / 2))
                sampl_pt = 75;

        /* tseg even = round down, odd = round up */
        for (
                tseg = (MIN_TSEG1 + MIN_TSEG2 + 2) * 2;
                tseg <= (MAX_TSEG2 + MAX_TSEG1 + 2) * 2 + 1;
                tseg++
        ) {
                brp = core_hz / ((1 + tseg / 2) * baud) + tseg % 2;
                if (
                        (brp <= 0) ||
                        ((brp > 256 * 1) && (brp <= 256 * 2) && (brp & 0x1)) ||
                        ((brp > 256 * 2) && (brp <= 256 * 4) && (brp & 0x3)) ||
                        ((brp > 256 * 4) && (brp <= 256 * 8) && (brp & 0x7)) ||
                        (brp > 256 * 8)
                )
                        continue;

                error = baud - core_hz / (brp * (1 + tseg / 2));
                if (error < 0) {
                        error = -error;
                }

                if (error <= best_error) {
                        best_error = error;
                        best_tseg = tseg / 2;
                        best_brp = brp - 1;
                }
        }

        if (best_error && (baud / best_error < 10)) {
                return -2;
        } else if (!timing)
                return 0;       /* nothing to store result in, but a valid bitrate can be calculated */

        tseg2 = best_tseg - (sampl_pt * (best_tseg + 1)) / 100;

        if (tseg2 < MIN_TSEG2) {
                tseg2 = MIN_TSEG2;
        }

        if (tseg2 > MAX_TSEG2) {
                tseg2 = MAX_TSEG2;
        }

        tseg1 = best_tseg - tseg2 - 2;

        if (tseg1 > MAX_TSEG1) {
                tseg1 = MAX_TSEG1;
                tseg2 = best_tseg - tseg1 - 2;
        }

        /* Get scaler and BRP from pseudo BRP */
        if (best_brp <= 256) {
                timing->scaler = best_brp;
                timing->bpr = 0;
        } else if (best_brp <= 256 * 2) {
                timing->scaler = ((best_brp + 1) >> 1) - 1;
                timing->bpr = 1;
        } else if (best_brp <= 256 * 4) {
                timing->scaler = ((best_brp + 1) >> 2) - 1;
                timing->bpr = 2;
        } else {
                timing->scaler = ((best_brp + 1) >> 3) - 1;
                timing->bpr = 3;
        }

        timing->ps1 = tseg1 + 1;
        timing->ps2 = tseg2;
        timing->rsj = sjw;

        return 0;
}

static int grcan_hw_read_try(
        struct grcan_priv *pDev,
        struct grcan_regs *regs,
        CANMsg * buffer,
        int max
)
{
        int i, j;
        CANMsg *dest;
        struct grcan_msg *source, tmp;
        unsigned int wp, rp, size, rxmax, addr;
        int trunk_msg_cnt;

        FUNCDBG();

        wp = READ_REG(&regs->rx0wr);
        rp = READ_REG(&regs->rx0rd);

        /*
         * Due to hardware wrap around simplification write pointer will
         * never reach the read pointer, at least a gap of 8 bytes.
         * The only time they are equal is when the read pointer has
         * reached the write pointer (empty buffer)
         *
         */
        if (wp != rp) {
                /* Not empty, we have received chars...
                 * Read as much as possible from DMA buffer
                 */
                size = READ_REG(&regs->rx0size);

                /* Get number of bytes available in RX buffer */
                trunk_msg_cnt = grcan_hw_rxavail(rp, wp, size);

                /* truncate size if user space buffer hasn't room for
                 * all received chars.
                 */
                if (trunk_msg_cnt > max)
                        trunk_msg_cnt = max;

                /* Read until i is 0 */
                i = trunk_msg_cnt;

                addr = (unsigned int)pDev->rx;
                source = (struct grcan_msg *)(addr + rp);
                dest = buffer;
                rxmax = addr + (size - GRCAN_MSG_SIZE);

                /* Read as many can messages as possible */
                while (i > 0) {
                        /* Read CAN message from DMA buffer */
                        tmp.head[0] = READ_DMA_WORD(&source->head[0]);
                        tmp.head[1] = READ_DMA_WORD(&source->head[1]);
                        if (tmp.head[1] & 0x4) {
                                DBGC(DBG_RX, "overrun\n");
                        }
                        if (tmp.head[1] & 0x2) {
                                DBGC(DBG_RX, "bus-off mode\n");
                        }
                        if (tmp.head[1] & 0x1) {
                                DBGC(DBG_RX, "error-passive mode\n");
                        }
                        /* Convert one grcan CAN message to one "software" CAN message */
                        dest->extended = tmp.head[0] >> 31;
                        dest->rtr = (tmp.head[0] >> 30) & 0x1;
                        if (dest->extended) {
                                dest->id = tmp.head[0] & 0x3fffffff;
                        } else {
                                dest->id = (tmp.head[0] >> 18) & 0xfff;
                        }
                        dest->len = tmp.head[1] >> 28;
                        for (j = 0; j < dest->len; j++)
                                dest->data[j] = READ_DMA_BYTE(&source->data[j]);

                        /* wrap around if neccessary */
                        source =
                            ((unsigned int)source >= rxmax) ?
                            (struct grcan_msg *)addr : source + 1;
                        dest++; /* straight user buffer */
                        i--;
                }
                {
                        /* A bus off interrupt may have occured after checking pDev->started */
                        SPIN_IRQFLAGS(oldLevel);

                        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
                        if (pDev->started == STATE_STARTED) {
                                regs->rx0rd = (unsigned int) source - addr;
                                regs->rx0ctrl = GRCAN_RXCTRL_ENABLE;
                        } else {
                                DBGC(DBG_STATE, "cancelled due to a BUS OFF error\n");
                                trunk_msg_cnt = state2err[pDev->started];
                        }
                        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
                }
                return trunk_msg_cnt;
        }
        return 0;
}

static int grcan_hw_write_try(
        struct grcan_priv *pDev,
        struct grcan_regs *regs,
        CANMsg * buffer,
        int count
)
{
        unsigned int rp, wp, size, txmax, addr;
        int ret;
        struct grcan_msg *dest;
        CANMsg *source;
        int space_left;
        unsigned int tmp;
        int i;

        DBGC(DBG_TX, "\n");
        /*FUNCDBG(); */

        rp = READ_REG(&regs->tx0rd);
        wp = READ_REG(&regs->tx0wr);
        size = READ_REG(&regs->tx0size);

        space_left = grcan_hw_txspace(rp, wp, size);

        /* is circular fifo full? */
        if (space_left < 1)
                return 0;

        /* Truncate size */
        if (space_left > count)
                space_left = count;
        ret = space_left;

        addr = (unsigned int)pDev->tx;

        dest = (struct grcan_msg *)(addr + wp);
        source = (CANMsg *) buffer;
        txmax = addr + (size - GRCAN_MSG_SIZE);

        while (space_left > 0) {
                /* Convert and write CAN message to DMA buffer */
                if (source->extended) {
                        tmp = (1 << 31) | (source->id & 0x3fffffff);
                } else {
                        tmp = (source->id & 0xfff) << 18;
                }
                if (source->rtr)
                        tmp |= (1 << 30);
                dest->head[0] = tmp;
                dest->head[1] = source->len << 28;
                for (i = 0; i < source->len; i++)
                        dest->data[i] = source->data[i];
                source++;       /* straight user buffer */
                dest =
                    ((unsigned int)dest >= txmax) ?
                    (struct grcan_msg *)addr : dest + 1;
                space_left--;
        }

        {
                /* A bus off interrupt may have occured after checking pDev->started */
                SPIN_IRQFLAGS(oldLevel);

                SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
                if (pDev->started == STATE_STARTED) {
                        regs->tx0wr = (unsigned int) dest - addr;
                        regs->tx0ctrl = GRCAN_TXCTRL_ENABLE;
                } else {
                        DBGC(DBG_STATE, "cancelled due to a BUS OFF error\n");
                        ret = state2err[pDev->started];
                }
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
        }
        return ret;
}

static int grcan_wait_rxdata(struct grcan_priv *pDev, int min)
{
        unsigned int wp, rp, size, irq;
        unsigned int irq_trunk, dataavail;
        int wait, state;
        SPIN_IRQFLAGS(oldLevel);

        FUNCDBG();

        /*** block until receive IRQ received
         * Set up a valid IRQ point so that an IRQ is received
         * when one or more messages are received
         */
        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        state = pDev->started;

        /* A bus off interrupt may have occured after checking pDev->started */
        if (state != STATE_STARTED) {
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
                if (state == STATE_BUSOFF) {
                        DBGC(DBG_STATE, "cancelled due to a BUS OFF error\n");
                } else if (state == STATE_AHBERR) {
                        DBGC(DBG_STATE, "cancelled due to a AHB error\n");
                } else {
                        DBGC(DBG_STATE, "cancelled due to STOP (unexpected) \n");
                }
                return state2err[state];
        }

        size = READ_REG(&pDev->regs->rx0size);
        rp = READ_REG(&pDev->regs->rx0rd);
        wp = READ_REG(&pDev->regs->rx0wr);

        /**** Calculate IRQ Pointer ****/
        irq = wp + min * GRCAN_MSG_SIZE;
        /* wrap irq around */
        if (irq >= size) {
                irq_trunk = irq - size;
        } else
                irq_trunk = irq;

        /* init IRQ HW */
        pDev->regs->rx0irq = irq_trunk;

        /* Clear pending Rx IRQ */
        pDev->regs->picr = GRCAN_RXIRQ_IRQ;

        wp = READ_REG(&pDev->regs->rx0wr);

        /* Calculate messages available */
        dataavail = grcan_hw_rxavail(rp, wp, size);

        if (dataavail < min) {
                /* Still empty, proceed with sleep - Turn on IRQ (unmask irq) */
                pDev->regs->imr = READ_REG(&pDev->regs->imr) | GRCAN_RXIRQ_IRQ;
                wait = 1;
        } else {
                /* enough message has been received, abort sleep - don't unmask interrupt */
                wait = 0;
        }
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        /* Wait for IRQ to fire only if has been triggered */
        if (wait) {
                if (
                        rtems_semaphore_obtain(
                                pDev->rx_sem,
                                RTEMS_WAIT,
                                RTEMS_NO_TIMEOUT
                        ) == RTEMS_UNSATISFIED
                ) {
                        DBGC(DBG_STATE, "UNSATISFIED\n");
                        /* Device driver has been closed or stopped, return with error status */
                        return state2err[pDev->started];
                }
        }

        return 0;
}

/* Wait until min bytes available in TX circular buffer. TXIRQ is used to pin
 * point the location of the CAN message corresponding to min.
 *
 * min must be at least WRAP_AROUND_TX_BYTES bytes less
 * than max buffer for this algo to work.
 *
 */
static int grcan_wait_txspace(struct grcan_priv *pDev, int min)
{
        int wait, state;
        unsigned int irq, rp, wp, size, space_left;
        unsigned int irq_trunk;
        SPIN_IRQFLAGS(oldLevel);

        DBGC(DBG_TX, "\n");
        /*FUNCDBG(); */

        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        state = pDev->started;
        /* A bus off interrupt may have occured after checking pDev->started */
        if (state != STATE_STARTED) {
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
                if (state == STATE_BUSOFF) {
                        DBGC(DBG_STATE, "cancelled due to a BUS OFF error\n");
                } else if (state == STATE_AHBERR) {
                        DBGC(DBG_STATE, "cancelled due to a AHB error\n");
                } else {
                        DBGC(DBG_STATE, "cancelled due to STOP (unexpected)\n");
                }
                return state2err[state];
        }

        pDev->regs->tx0ctrl = GRCAN_TXCTRL_ENABLE;

        size = READ_REG(&pDev->regs->tx0size);
        wp = READ_REG(&pDev->regs->tx0wr);

        rp = READ_REG(&pDev->regs->tx0rd);

        /**** Calculate IRQ Pointer ****/
        irq = rp + min * GRCAN_MSG_SIZE;
        /* wrap irq around */
        if (irq >= size) {
                irq_trunk = irq - size;
        } else
                irq_trunk = irq;

        /* trigger HW to do a IRQ when enough room in buffer */
        pDev->regs->tx0irq = irq_trunk;

        /* Clear pending Tx IRQ */
        pDev->regs->picr = GRCAN_TXIRQ_IRQ;

        /* One problem, if HW already gone past IRQ place the IRQ will
         * never be received resulting in a thread hang. We check if so
         * before proceeding.
         *
         * has the HW already gone past the IRQ generation place?
         *  == does min fit info tx buffer?
         */
        rp = READ_REG(&pDev->regs->tx0rd);

        space_left = grcan_hw_txspace(rp, wp, size);

        if (space_left < min) {
                /* Still too full, proceed with sleep - Turn on IRQ (unmask irq) */
                pDev->regs->imr = READ_REG(&pDev->regs->imr) | GRCAN_TXIRQ_IRQ;
                wait = 1;
        } else {
                /* There are enough room in buffer, abort wait - don't unmask interrupt */
                wait = 0;
        }
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        /* Wait for IRQ to fire only if it has been triggered */
        if (wait) {
                if (rtems_semaphore_obtain(pDev->tx_sem, RTEMS_WAIT, RTEMS_NO_TIMEOUT) ==
                    RTEMS_UNSATISFIED) {
                        /* Device driver has flushed us, this may be due to another thread has
                         * closed the device, this is to avoid deadlock */
                        DBGC(DBG_STATE, "UNSATISFIED\n");
                        return state2err[pDev->started];
                }
        }

        /* At this point the TxIRQ has been masked, we ned not to mask it */
        return 0;
}

static int grcan_tx_flush(struct grcan_priv *pDev)
{
        int wait, state;
        unsigned int rp, wp;
        SPIN_IRQFLAGS(oldLevel);
        FUNCDBG();

        /* loop until all data in circular buffer has been read by hw.
         * (write pointer != read pointer )
         *
         * Hardware doesn't update write pointer - we do
         */
        while (
                (wp = READ_REG(&pDev->regs->tx0wr)) !=
                (rp = READ_REG(&pDev->regs->tx0rd))
        ) {
                /* Wait for TX empty IRQ */
                SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
                state = pDev->started;

                /* A bus off interrupt may have occured after checking pDev->started */
                if (state != STATE_STARTED) {
                        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
                        if (state == STATE_BUSOFF) {
                                DBGC(DBG_STATE, "cancelled due to a BUS OFF error\n");
                        } else if (state == STATE_AHBERR) {
                                DBGC(DBG_STATE, "cancelled due to a AHB error\n");
                        } else {
                                DBGC(DBG_STATE, "cancelled due to STOP (unexpected)\n");
                        }
                        return state2err[state];
                }

                /* Clear pending TXEmpty IRQ */
                pDev->regs->picr = GRCAN_TXEMPTY_IRQ;

                if (wp != READ_REG(&pDev->regs->tx0rd)) {
                        /* Still not empty, proceed with sleep - Turn on IRQ (unmask irq) */
                        pDev->regs->imr =
                            READ_REG(&pDev->regs->imr) | GRCAN_TXEMPTY_IRQ;
                        wait = 1;
                } else {
                        /* TX fifo is empty */
                        wait = 0;
                }
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
                if (!wait)
                        break;

                /* Wait for IRQ to wake us */
                if (rtems_semaphore_obtain
                    (pDev->txempty_sem, RTEMS_WAIT,
                     RTEMS_NO_TIMEOUT) == RTEMS_UNSATISFIED) {
                        DBGC(DBG_STATE, "UNSATISFIED\n");
                        return state2err[pDev->started];
                }
        }
        return 0;
}

static int grcan_alloc_buffers(struct grcan_priv *pDev, int rx, int tx)
{
        unsigned int adr;
        FUNCDBG();

        if ( tx ) {
                adr = (unsigned int)pDev->txbuf_adr;
                if (adr & 0x1) {
                        /* User defined "remote" address. Translate it into
                         * a CPU accessible address
                         */
                        pDev->_tx_hw = (void *)(adr & ~0x1);
                        drvmgr_translate_check(
                                pDev->dev,
                                DMAMEM_TO_CPU,
                                (void *)pDev->_tx_hw,
                                (void **)&pDev->_tx,
                                pDev->txbuf_size);
                        pDev->tx = (struct grcan_msg *)pDev->_tx;
                } else {
                        if (adr == 0) {
                                pDev->_tx = malloc(pDev->txbuf_size +
                                                   BUFFER_ALIGNMENT_NEEDS);
                                if (!pDev->_tx)
                                        return -1;
                        } else {
                                /* User defined "cou-local" address. Translate
                                 * it into a CPU accessible address
                                 */
                                pDev->_tx = (void *)adr;
                        }
                        /* Align TX buffer */
                        pDev->tx = (struct grcan_msg *)
                                   (((unsigned int)pDev->_tx +
                                   (BUFFER_ALIGNMENT_NEEDS-1)) &
                                   ~(BUFFER_ALIGNMENT_NEEDS-1));

                        /* Translate address into an hardware accessible
                         * address
                         */
                        drvmgr_translate_check(
                                pDev->dev,
                                CPUMEM_TO_DMA,
                                (void *)pDev->tx,
                                (void **)&pDev->_tx_hw,
                                pDev->txbuf_size);
                }
        }

        if ( rx ) {
                adr = (unsigned int)pDev->rxbuf_adr;
                if (adr & 0x1) {
                        /* User defined "remote" address. Translate it into
                         * a CPU accessible address
                         */
                        pDev->_rx_hw = (void *)(adr & ~0x1);
                        drvmgr_translate_check(
                                pDev->dev,
                                DMAMEM_TO_CPU,
                                (void *)pDev->_rx_hw,
                                (void **)&pDev->_rx,
                                pDev->rxbuf_size);
                        pDev->rx = (struct grcan_msg *)pDev->_rx;
                } else {
                        if (adr == 0) {
                                pDev->_rx = malloc(pDev->rxbuf_size +
                                                   BUFFER_ALIGNMENT_NEEDS);
                                if (!pDev->_rx)
                                        return -1;
                        } else {
                                /* User defined "cou-local" address. Translate
                                 * it into a CPU accessible address
                                 */
                                pDev->_rx = (void *)adr;
                        }
                        /* Align RX buffer */
                        pDev->rx = (struct grcan_msg *)
                                   (((unsigned int)pDev->_rx +
                                   (BUFFER_ALIGNMENT_NEEDS-1)) &
                                   ~(BUFFER_ALIGNMENT_NEEDS-1));

                        /* Translate address into an hardware accessible
                         * address
                         */
                        drvmgr_translate_check(
                                pDev->dev,
                                CPUMEM_TO_DMA,
                                (void *)pDev->rx,
                                (void **)&pDev->_rx_hw,
                                pDev->rxbuf_size);
                }
        }
        return 0;
}

static void grcan_free_buffers(struct grcan_priv *pDev, int rx, int tx)
{
        FUNCDBG();

        if (tx && pDev->_tx) {
                free(pDev->_tx);
                pDev->_tx = NULL;
                pDev->tx = NULL;
        }

        if (rx && pDev->_rx) {
                free(pDev->_rx);
                pDev->_rx = NULL;
                pDev->rx = NULL;
        }
}

int grcan_dev_count(void)
{
        return grcan_count;
}

void *grcan_open_by_name(char *name, int *dev_no)
{
        int i;
        for (i = 0; i < grcan_count; i++){
                struct grcan_priv *pDev;

                pDev = priv_tab[i];
                if (NULL == pDev) {
                        continue;
                }
                if (strncmp(pDev->devName, name, NELEM(pDev->devName)) == 0) {
                        if (dev_no)
                                *dev_no = i;
                        return grcan_open(i);
                }
        }
        return NULL;
}

void *grcan_open(int dev_no)
{
        struct grcan_priv *pDev;
        void *ret;
        union drvmgr_key_value *value;

        FUNCDBG();

        if (grcan_count == 0 || (grcan_count <= dev_no)) {
                return NULL;
        }

        pDev = priv_tab[dev_no];

        /* Wait until we get semaphore */
        if (rtems_semaphore_obtain(pDev->dev_sem, RTEMS_WAIT, RTEMS_NO_TIMEOUT)
            != RTEMS_SUCCESSFUL) {
                return NULL;
        }

        /* is device busy/taken? */
        if ( pDev->open ) {
                ret = NULL;
                goto out;
        }

        SPIN_INIT(&pDev->devlock, pDev->devName);

        /* Mark device taken */
        pDev->open = 1;

        pDev->txblock = pDev->rxblock = 1;
        pDev->txcomplete = pDev->rxcomplete = 0;
        pDev->started = STATE_STOPPED;
        pDev->config_changed = 1;
        pDev->config.silent = 0;
        pDev->config.abort = 0;
        pDev->config.selection.selection = 0;
        pDev->config.selection.enable0 = 0;
        pDev->config.selection.enable1 = 1;
        pDev->flushing = 0;
        pDev->rx = pDev->_rx = NULL;
        pDev->tx = pDev->_tx = NULL;
        pDev->txbuf_adr = 0;
        pDev->rxbuf_adr = 0;
        pDev->txbuf_size = TX_BUF_SIZE;
        pDev->rxbuf_size = RX_BUF_SIZE;

        /* Override default buffer sizes if available from bus resource */
        value = drvmgr_dev_key_get(pDev->dev, "txBufSize", DRVMGR_KT_INT);
        if ( value )
                pDev->txbuf_size = value->i;

        value = drvmgr_dev_key_get(pDev->dev, "rxBufSize", DRVMGR_KT_INT);
        if ( value )
                pDev->rxbuf_size = value->i;

        value = drvmgr_dev_key_get(pDev->dev, "txBufAdr", DRVMGR_KT_POINTER);
        if ( value )
                pDev->txbuf_adr = value->ptr;

        value = drvmgr_dev_key_get(pDev->dev, "rxBufAdr", DRVMGR_KT_POINTER);
        if ( value )
                pDev->rxbuf_adr = value->ptr;

        DBG("Defaulting to rxbufsize: %d, txbufsize: %d\n",RX_BUF_SIZE,TX_BUF_SIZE);

        /* Default to accept all messages */
        pDev->afilter.mask = 0x00000000;
        pDev->afilter.code = 0x00000000;

        /* Default to disable sync messages (only trigger when id is set to all ones) */
        pDev->sfilter.mask = 0xffffffff;
        pDev->sfilter.code = 0x00000000;

        /* Calculate default timing register values */
        grcan_calc_timing(GRCAN_DEFAULT_BAUD,pDev->corefreq_hz,GRCAN_SAMPLING_POINT,&pDev->config.timing);

        if ( grcan_alloc_buffers(pDev,1,1) ) {
                ret = NULL;
                goto out;
        }

        /* Clear statistics */
        memset(&pDev->stats,0,sizeof(struct grcan_stats));

        ret = pDev;
out:
        rtems_semaphore_release(pDev->dev_sem);
        return ret;
}

int grcan_close(void *d)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        grcan_stop(d);

        grcan_hw_reset(pDev->regs);

        grcan_free_buffers(pDev,1,1);

        /* Mark Device as closed */
        pDev->open = 0;

        return 0;
}

int grcan_read(void *d, CANMsg *msg, size_t ucount)
{
        struct grcan_priv *pDev = d;
        CANMsg *dest;
        unsigned int count, left;
        int nread;
        int req_cnt;

        FUNCDBG();

        dest = msg;
        req_cnt = ucount;

        if ( (!dest) || (req_cnt<1) )
                return GRCAN_RET_INVARG;

        if (pDev->started != STATE_STARTED) {
                return GRCAN_RET_NOTSTARTED;
        }

        DBGC(DBG_RX, "grcan_read [%p]: buf: %p len: %u\n", d, msg, (unsigned int) ucount);

        nread = grcan_hw_read_try(pDev,pDev->regs,dest,req_cnt);
        if (nread < 0) {
                return nread;
        }
        count = nread;
        if ( !( pDev->rxblock && pDev->rxcomplete && (count!=req_cnt) ) ){
                if ( count > 0 ) {
                        /* Successfully received messages (at least one) */
                        return count;
                }

                /* nothing read, shall we block? */
                if ( !pDev->rxblock ) {
                        /* non-blocking mode */
                        return GRCAN_RET_TIMEOUT;
                }
        }

        while (count == 0 || (pDev->rxcomplete && (count!=req_cnt))) {
                if (!pDev->rxcomplete) {
                        left = 1; /* return as soon as there is one message available */
                } else {
                        left = req_cnt - count;     /* return as soon as all data are available */

                        /* never wait for more than the half the maximum size of the receive buffer 
                         * Why? We need some time to copy buffer before to catch up with hw,
                         * otherwise we would have to copy everything when the data has been
                         * received.
                         */
                        if (left > ((pDev->rxbuf_size/GRCAN_MSG_SIZE) / 2)){
                                left = (pDev->rxbuf_size/GRCAN_MSG_SIZE) / 2;
                        }
                }

                nread = grcan_wait_rxdata(pDev, left);
                if (nread) {
                        /* The wait has been aborted, probably due to 
                         * the device driver has been closed by another
                         * thread or a bus-off. Return error code.
                         */
                        return nread;
                }

                /* Try read bytes from circular buffer */
                nread = grcan_hw_read_try(
                                pDev,
                                pDev->regs,
                                dest+count,
                                req_cnt-count);

                if (nread < 0) {
                        /* The read was aborted by bus-off. */
                        return nread;
                }
                count += nread;
        }
        /* no need to unmask IRQ as IRQ Handler do that for us. */
        return count;
}

int grcan_write(void *d, CANMsg *msg, size_t ucount)
{
        struct grcan_priv *pDev = d;
        CANMsg *source;
        unsigned int count, left;
        int nwritten;
        int req_cnt;

        DBGC(DBG_TX,"\n");

        if ((pDev->started != STATE_STARTED) || pDev->config.silent || pDev->flushing)
                return GRCAN_RET_NOTSTARTED;

        req_cnt = ucount;
        source = (CANMsg *) msg;

        /* check proper length and buffer pointer */
        if (( req_cnt < 1) || (source == NULL) ){
                return GRCAN_RET_INVARG;
        }

        nwritten = grcan_hw_write_try(pDev,pDev->regs,source,req_cnt);
        if (nwritten < 0) {
                return nwritten;
        }
        count = nwritten;
        if ( !(pDev->txblock && pDev->txcomplete && (count!=req_cnt)) ) {
                if ( count > 0 ) {
                        /* Successfully transmitted chars (at least one char) */
                        return count;
                }

                /* nothing written, shall we block? */
                if ( !pDev->txblock ) {
                        /* non-blocking mode */
                        return GRCAN_RET_TIMEOUT;
                }
        }

        /* if in txcomplete mode we need to transmit all chars */
        while((count == 0) || (pDev->txcomplete && (count!=req_cnt)) ){
                /*** block until room to fit all or as much of transmit buffer as possible
                 * IRQ comes. Set up a valid IRQ point so that an IRQ is received 
                 * when we can put a chunk of data into transmit fifo
                 */
                if ( !pDev->txcomplete ){
                        left = 1; /* wait for anything to fit buffer */
                }else{
                        left = req_cnt - count; /* wait for all data to fit in buffer */

                        /* never wait for more than the half the maximum size of the transmit
                         * buffer 
                         * Why? We need some time to fill buffer before hw catches up.
                         */
                        if ( left > ((pDev->txbuf_size/GRCAN_MSG_SIZE)/2) ){
                                left = (pDev->txbuf_size/GRCAN_MSG_SIZE)/2;
                        }
                }

                nwritten = grcan_wait_txspace(pDev,left);
                /* Wait until more room in transmit buffer */
                if ( nwritten ) {
                        /* The wait has been aborted, probably due to 
                         * the device driver has been closed by another
                         * thread. To avoid deadlock we return directly
                         * with error status.
                         */
                        return nwritten;
                }

                if ( pDev->txerror ){
                        /* Return number of bytes sent, compare write pointers */
                        pDev->txerror = 0;
#if 0 
#error HANDLE AMBA error
#endif
                }

                /* Try read bytes from circular buffer */
                nwritten = grcan_hw_write_try(
                        pDev,
                        pDev->regs,
                        source+count,
                        req_cnt-count);

                if (nwritten < 0) {
                        /* Write was aborted by bus-off. */
                        return nwritten;
                }
                count += nwritten;
        }
        /* no need to unmask IRQ as IRQ Handler do that for us. */

        return count;
}

int grcan_start(void *d)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if (grcan_get_state(d) == STATE_STARTED) {
                return -1;
        }

        if ( (grcan_hw_start(pDev)) != RTEMS_SUCCESSFUL ){
                return -2;
        }

        /* Read and write are now open... */
        pDev->started = STATE_STARTED;
        DBGC(DBG_STATE, "STOPPED|BUSOFF|AHBERR->STARTED\n");

        /* Register interrupt routine and enable IRQ at IRQ ctrl */
        drvmgr_interrupt_register(pDev->dev, 0, pDev->devName,
                                        grcan_interrupt, pDev);

        return 0;
}

int grcan_stop(void *d)
{
        struct grcan_priv *pDev = d;
        SPIN_IRQFLAGS(oldLevel);
        int do_sw_stop;

        FUNCDBG();

        if (pDev->started == STATE_STOPPED)
                return -1;

        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        if (pDev->started == STATE_STARTED) {
                grcan_hw_stop(pDev);
                do_sw_stop = 1;
                DBGC(DBG_STATE, "STARTED->STOPPED\n");
        } else {
                /*
                 * started == STATE_[STOPPED|BUSOFF|AHBERR] so grcan_hw_stop()
                 * might already been called from ISR.
                 */
                DBGC(DBG_STATE, "[STOPPED|BUSOFF|AHBERR]->STOPPED\n");
                do_sw_stop = 0;
        }
        pDev->started = STATE_STOPPED;
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        if (do_sw_stop)
                grcan_sw_stop(pDev);

        /* Disable interrupts */
        drvmgr_interrupt_unregister(pDev->dev, 0, grcan_interrupt, pDev);

        return 0;
}

int grcan_get_state(void *d)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        return pDev->started;
}

int grcan_flush(void *d)
{
        struct grcan_priv *pDev = d;
        int tmp;

        FUNCDBG();

        if ((pDev->started != STATE_STARTED) || pDev->flushing || pDev->config.silent)
                return -1;

        pDev->flushing = 1;
        tmp = grcan_tx_flush(pDev);
        pDev->flushing = 0;
        if ( tmp ) {
                /* The wait has been aborted, probably due to
                 * the device driver has been closed by another
                 * thread.
                 */
                return -1;
        }

        return 0;
}

int grcan_set_silent(void* d, int silent)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if (pDev->started == STATE_STARTED)
                return -1;

        pDev->config.silent = silent;
        pDev->config_changed = 1;

        return 0;
}

int grcan_set_abort(void* d, int abort)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if (pDev->started == STATE_STARTED)
                return -1;

        pDev->config.abort = abort;
        /* This Configuration parameter doesn't need HurriCANe reset
         * ==> no pDev->config_changed = 1;
         */

        return 0;
}

int grcan_set_selection(void *d, const struct grcan_selection *selection)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if (pDev->started == STATE_STARTED)
                return -1;

        if ( !selection )
                return -2;

        pDev->config.selection = *selection;
        pDev->config_changed = 1;

        return 0;
}

int grcan_set_rxblock(void *d, int block)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        pDev->rxblock = block;

        return 0;
}

int grcan_set_txblock(void *d, int block)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        pDev->txblock = block;

        return 0;
}

int grcan_set_txcomplete(void *d, int complete)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        pDev->txcomplete = complete;

        return 0;
}

int grcan_set_rxcomplete(void *d, int complete)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        pDev->rxcomplete = complete;

        return 0;
}

int grcan_get_stats(void *d, struct grcan_stats *stats)
{
        struct grcan_priv *pDev = d;
        SPIN_IRQFLAGS(oldLevel);

        FUNCDBG();

        if ( !stats )
                return -1;

        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        *stats = pDev->stats;
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        return 0;
}

int grcan_clr_stats(void *d)
{
        struct grcan_priv *pDev = d;
        SPIN_IRQFLAGS(oldLevel);

        FUNCDBG();

        SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
        memset(&pDev->stats,0,sizeof(struct grcan_stats));
        SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);

        return 0;
}

int grcan_set_speed(void *d, unsigned int speed)
{
        struct grcan_priv *pDev = d;
        struct grcan_timing timing;
        int ret;

        FUNCDBG();

        /* cannot change speed during run mode */
        if (pDev->started == STATE_STARTED)
                return -1;

        /* get speed rate from argument */
        ret = grcan_calc_timing(speed, pDev->corefreq_hz, GRCAN_SAMPLING_POINT, &timing);
        if ( ret )
                return -2;

        /* save timing/speed */
        pDev->config.timing = timing;
        pDev->config_changed = 1;

        return 0;
}

int grcan_set_btrs(void *d, const struct grcan_timing *timing)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        /* Set BTR registers manually
         * Read GRCAN/HurriCANe Manual.
         */
        if (pDev->started == STATE_STARTED)
                return -1;

        if ( !timing )
                return -2;

        pDev->config.timing = *timing;
        pDev->config_changed = 1;

        return 0;
}

int grcan_set_afilter(void *d, const struct grcan_filter *filter)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if ( !filter ){
                /* Disable filtering - let all messages pass */
                pDev->afilter.mask = 0x0;
                pDev->afilter.code = 0x0;
        }else{
                /* Save filter */
                pDev->afilter = *filter;
        }
        /* Set hardware acceptance filter */
        grcan_hw_accept(pDev->regs,&pDev->afilter);

        return 0;
}

int grcan_set_sfilter(void *d, const struct grcan_filter *filter)
{
        struct grcan_priv *pDev = d;
        SPIN_IRQFLAGS(oldLevel);

        FUNCDBG();

        if ( !filter ){
                /* disable TX/RX SYNC filtering */
                pDev->sfilter.mask = 0xffffffff;
                pDev->sfilter.mask = 0;

                 /* disable Sync interrupt */
                SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
                pDev->regs->imr = READ_REG(&pDev->regs->imr) & ~(GRCAN_RXSYNC_IRQ|GRCAN_TXSYNC_IRQ);
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
        }else{
                /* Save filter */
                pDev->sfilter = *filter;

                /* Enable Sync interrupt */
                SPIN_LOCK_IRQ(&pDev->devlock, oldLevel);
                pDev->regs->imr = READ_REG(&pDev->regs->imr) | (GRCAN_RXSYNC_IRQ|GRCAN_TXSYNC_IRQ);
                SPIN_UNLOCK_IRQ(&pDev->devlock, oldLevel);
        }
        /* Set Sync RX/TX filter */
        grcan_hw_sync(pDev->regs,&pDev->sfilter);

        return 0;
}

int grcan_get_status(void* d, unsigned int *data)
{
        struct grcan_priv *pDev = d;

        FUNCDBG();

        if ( !data )
                return -1;

        /* Read out the statsu register from the GRCAN core */
        data[0] = READ_REG(&pDev->regs->stat);

        return 0;
}

/* Error indicators */
#define GRCAN_IRQ_ERRORS \
                (GRCAN_RXAHBERR_IRQ | GRCAN_TXAHBERR_IRQ | GRCAN_OFF_IRQ)
#define GRCAN_STAT_ERRORS (GRCAN_STAT_AHBERR | GRCAN_STAT_OFF)
/* Warning & RX/TX sync indicators */
#define GRCAN_IRQ_WARNS \
                (GRCAN_ERR_IRQ | GRCAN_OR_IRQ | GRCAN_TXLOSS_IRQ | \
                 GRCAN_RXSYNC_IRQ | GRCAN_TXSYNC_IRQ)
#define GRCAN_STAT_WARNS (GRCAN_STAT_OR | GRCAN_STAT_PASS)

/* Handle the IRQ */
static void grcan_interrupt(void *arg)
{
        struct grcan_priv *pDev = arg;
        unsigned int status = READ_REG(&pDev->regs->pimsr);
        unsigned int canstat = READ_REG(&pDev->regs->stat);
        unsigned int imr_clear;
        SPIN_ISR_IRQFLAGS(irqflags);

        /* Spurious IRQ call? */
        if ( !status && !canstat )
                return;

        if (pDev->started != STATE_STARTED) {
                DBGC(DBG_STATE, "not STARTED (unexpected interrupt)\n");
                pDev->regs->picr = status;
                return;
        }

        FUNCDBG();

        if ( (status & GRCAN_IRQ_ERRORS) || (canstat & GRCAN_STAT_ERRORS) ) {
                /* Bus-off condition interrupt
                 * The link is brought down by hardware, we wake all threads
                 * that is blocked in read/write calls and stop futher calls
                 * to read/write until user has called ioctl(fd,START,0).
                 */
                SPIN_LOCK(&pDev->devlock, irqflags);
                DBGC(DBG_STATE, "STARTED->BUSOFF|AHBERR\n");
                pDev->stats.ints++;
                if ((status & GRCAN_OFF_IRQ) || (canstat & GRCAN_STAT_OFF)) {
                        /* CAN Bus-off interrupt */
                        DBGC(DBG_STATE, "BUSOFF: status: 0x%x, canstat: 0x%x\n",
                                status, canstat);
                        pDev->started = STATE_BUSOFF;
                        pDev->stats.busoff_cnt++;
                } else {
                        /* RX or Tx AHB Error interrupt */
                        printk("AHBERROR: status: 0x%x, canstat: 0x%x\n",
                                status, canstat);
                        pDev->started = STATE_AHBERR;
                        pDev->stats.ahberr_cnt++;
                }
                grcan_hw_stop(pDev); /* this mask all IRQ sources */
                pDev->regs->picr = 0x1ffff; /* clear all interrupts */
                /*
                 * Prevent driver from affecting bus. Driver can be started
                 * again with grcan_start().
                 */
                SPIN_UNLOCK(&pDev->devlock, irqflags);

                /* flush semaphores to wake blocked threads */
                grcan_sw_stop(pDev);

                /*
                 * NOTE: Another interrupt may be pending now so ISR could be
                 * executed one more time aftert this (first) return.
                 */
                return;
        }

        /* Mask interrupts in one place under spin-lock. */
        imr_clear = status & (GRCAN_RXIRQ_IRQ | GRCAN_TXIRQ_IRQ | GRCAN_TXEMPTY_IRQ);

        SPIN_LOCK(&pDev->devlock, irqflags);

        /* Increment number of interrupts counter */
        pDev->stats.ints++;
        if ((status & GRCAN_IRQ_WARNS) || (canstat & GRCAN_STAT_WARNS)) {

                if ( (status & GRCAN_ERR_IRQ) || (canstat & GRCAN_STAT_PASS) ) {
                        /* Error-Passive interrupt */
                        pDev->stats.passive_cnt++;
                }

                if ( (status & GRCAN_OR_IRQ) || (canstat & GRCAN_STAT_OR) ) {
                        /* Over-run during reception interrupt */
                        pDev->stats.overrun_cnt++;
                }

                if ( status & GRCAN_TXLOSS_IRQ ) {
                        pDev->stats.txloss_cnt++;
                }

                if ( status & GRCAN_TXSYNC_IRQ ) {
                        /* TxSync message transmitted interrupt */
                        pDev->stats.txsync_cnt++;
                }

                if ( status & GRCAN_RXSYNC_IRQ ) {
                        /* RxSync message received interrupt */
                        pDev->stats.rxsync_cnt++;
                }
        }

        if (imr_clear) {
                pDev->regs->imr = READ_REG(&pDev->regs->imr) & ~imr_clear;

                SPIN_UNLOCK(&pDev->devlock, irqflags);

                if ( status & GRCAN_RXIRQ_IRQ ) {
                        /* RX IRQ pointer interrupt */
                        rtems_semaphore_release(pDev->rx_sem);
                }

                if ( status & GRCAN_TXIRQ_IRQ ) {
                        /* TX IRQ pointer interrupt */
                        rtems_semaphore_release(pDev->tx_sem);
                }

                if (status & GRCAN_TXEMPTY_IRQ ) {
                        rtems_semaphore_release(pDev->txempty_sem);
                }
        } else {
                SPIN_UNLOCK(&pDev->devlock, irqflags);
        }

        /* Clear IRQs */
        pDev->regs->picr = status;
}