source: rtems/c/src/lib/libbsp/powerpc/shared/clock/clock.c @ 6a0898b

/**
 * @file
 *
 * @ingroup powerpc_shared
 *
 * @brief Source file for a clock driver.
 */

/*
 * Copyright (c) 2008
 * Embedded Brains GmbH
 * Obere Lagerstr. 30
 * D-82178 Puchheim
 * Germany
 * rtems@embedded-brains.de
 *
 * The license and distribution terms for this file may be found in the file
 * LICENSE in this distribution or at http://www.rtems.com/license/LICENSE.
 */

#include <rtems/libio.h>
#include <rtems/clockdrv.h>

#include <libcpu/powerpc-utility.h>
#include <libcpu/raw_exception.h>

#include <bsp/ppc_exc_bspsupp.h>

#define RTEMS_STATUS_CHECKS_USE_PRINTK

#include <rtems/status-checks.h>

/*
 * This variable must be defined in the BSP and valid before clock driver
 * initialization.  The clicks refer to the decrementer and time base.
 */
extern uint32_t bsp_clicks_per_usec;

#define PPC_CLOCK_DECREMENTER_MAX UINT32_MAX

volatile uint32_t Clock_driver_ticks = 0;

rtems_device_major_number rtems_clock_major = -1;

rtems_device_minor_number rtems_clock_minor = -1;

static uint32_t ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;

static uint32_t ppc_clock_next_time_base = 0;

static void ppc_clock_no_tick()
{
        /* Do nothing */
}

static void (*ppc_clock_tick)() = ppc_clock_no_tick;

int ppc_clock_exception_handler( BSP_Exception_frame *frame, unsigned number)
{
        uint32_t reg1;
        uint32_t reg2;
        uint32_t reg3;
        uint32_t msr;

        /* Set new decrementer value according to a reference time base */
        asm volatile (
                "lwz %0, ppc_clock_next_time_base@sdarel(13);"
                "lwz %1, ppc_clock_decrementer_value@sdarel(13);"
                "mftb %2;"
                "add %0, %0, %1;"
                "subf %1, %2, %0;"
                "stw %0, ppc_clock_next_time_base@sdarel(13);"
                "mtdec %1;"
                : "=r" (reg1), "=r" (reg2), "=r" (reg3)
        );

        /* Increment clock ticks */
        Clock_driver_ticks += 1;

        /* Enable external exceptions */
        msr = ppc_external_exceptions_enable();

        /* Call clock ticker  */
        ppc_clock_tick();

        /* Restore machine state */
        ppc_external_exceptions_disable( msr);

        return 0;
}

int ppc_clock_exception_handler_classic( BSP_Exception_frame *frame, unsigned number)
{
        uint32_t reg1;
        uint32_t reg2;
        uint32_t msr;

        /* Set new decrementer value */
        asm volatile(
                "lwz %1, ppc_clock_decrementer_value@sdarel(13);"
                "mfdec %0;"
                "add %0, %0, %1;"
                "mtdec %0"
                : "=r" (reg1), "=r" (reg2)
        );

        /* Increment clock ticks */
        Clock_driver_ticks += 1;

        /* Enable external exceptions */
        msr = ppc_external_exceptions_enable();

        /* Call clock ticker  */
        ppc_clock_tick();

        /* Restore machine state */
        ppc_external_exceptions_disable( msr);

        return 0;
}

int ppc_clock_exception_handler_booke( BSP_Exception_frame *frame, unsigned number)
{
        uint32_t msr;

        /* Acknowledge decrementer request */
        PPC_SET_SPECIAL_PURPOSE_REGISTER( BOOKE_TSR, BOOKE_TSR_DIS);

        /* Increment clock ticks */
        Clock_driver_ticks += 1;

        /* Enable external exceptions */
        msr = ppc_external_exceptions_enable();

        /* Call clock ticker  */
        ppc_clock_tick();

        /* Restore machine state */
        ppc_external_exceptions_disable( msr);

        return 0;
}

int ppc_clock_exception_handler_e300( BSP_Exception_frame *frame, unsigned number)
{
        uint32_t msr;

        /* Increment clock ticks */
        Clock_driver_ticks += 1;

        /* Enable external exceptions */
        msr = ppc_external_exceptions_enable();

        /* Call clock ticker  */
        ppc_clock_tick();

        /* Restore machine state */
        ppc_external_exceptions_disable( msr);

        return 0;
}

uint32_t ppc_clock_nanoseconds_since_last_tick()
{
        return ((ppc_clock_decrementer_value - ppc_decrementer_register()) * 1000) / bsp_clicks_per_usec;
}

void Clock_exit()
{
        /* Set the decrementer to the maximum value */
        ppc_set_decrementer_register( PPC_CLOCK_DECREMENTER_MAX);

        /* Use default clock handler */
        ppc_clock_tick = ppc_clock_no_tick;
}

rtems_device_driver Clock_initialize( rtems_device_major_number major, rtems_device_minor_number minor, void *arg)
{
        /* Current CPU type */
        ppc_cpu_id_t cpu_type = get_ppc_cpu_type();

        /* Make major/minor available to others such as shared memory driver */
        rtems_clock_major = major;
        rtems_clock_minor = minor;

        /*
         * Set default ticker.
         * 
         * The function rtems_clock_tick() returns a status code.  This value
         * will be discarded since the RTEMS documentation claims that it is
         * always successful.
         */
        ppc_clock_tick = (void (*)()) rtems_clock_tick;

        /* Set the decrementer to the maximum value */
        ppc_set_decrementer_register( PPC_CLOCK_DECREMENTER_MAX);

        /* Decrementer value */
        ppc_clock_decrementer_value = bsp_clicks_per_usec * rtems_configuration_get_microseconds_per_tick() - 1;

        /* Check decrementer value */
        if (ppc_clock_decrementer_value == 0) {
                ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;
                SYSLOG_ERROR( "Decrementer value would be zero, will be set to maximum value instead\n");
        }

        /* Set the nanoseconds since last tick handler */
        rtems_clock_set_nanoseconds_extension( ppc_clock_nanoseconds_since_last_tick);

        if (ppc_cpu_is_bookE()) {
                /* Set decrementer auto-reload value */
                PPC_SET_SPECIAL_PURPOSE_REGISTER( BOOKE_DECAR, ppc_clock_decrementer_value);

                /* Install exception handler */
                ppc_exc_set_handler( ASM_BOOKE_DEC_VECTOR, ppc_clock_exception_handler_booke);

                /* Enable decrementer and auto-reload */
                PPC_SET_SPECIAL_PURPOSE_REGISTER_BITS( BOOKE_TCR, BOOKE_TCR_DIE | BOOKE_TCR_ARE);
        } else if (cpu_type == PPC_e300c2 || cpu_type == PPC_e300c3) {
                /* TODO: Not tested for e300c2 */

                /* Enable auto-reload */
                PPC_SET_SPECIAL_PURPOSE_REGISTER_BITS( HID0, 0x00000040);

                /* Install exception handler */
                ppc_exc_set_handler( ASM_DEC_VECTOR, ppc_clock_exception_handler_e300);
        } else {
                /* Here the decrementer value is actually the interval */
                ++ppc_clock_decrementer_value;

                /* Initialize next time base */
                ppc_clock_next_time_base = ppc_time_base() + ppc_clock_decrementer_value;

                /* Install exception handler */
                ppc_exc_set_handler( ASM_DEC_VECTOR, ppc_clock_exception_handler);
        }

        /* Set the decrementer value */
        ppc_set_decrementer_register( ppc_clock_decrementer_value);

        return RTEMS_SUCCESSFUL;
}

rtems_device_driver Clock_control( rtems_device_major_number major, rtems_device_minor_number minor, void *arg)
{
        rtems_libio_ioctl_args_t *io = arg;

        if (io == NULL) {
                return RTEMS_SUCCESSFUL;
        }

        if (io->command == rtems_build_name( 'I', 'S', 'R', ' ')) {
                ppc_clock_tick();
        } else if (io->command == rtems_build_name( 'N', 'E', 'W', ' ')) {
                if (io->buffer != NULL) {
                        ppc_clock_tick = io->buffer;
                } else {
                        ppc_clock_tick = ppc_clock_no_tick;
                }
        }

        return RTEMS_SUCCESSFUL;
}