source: rtems/c/src/lib/libbsp/powerpc/shared/clock/clock.c @ 8bb00ac

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

/*
 * Copyright (c) 2008-2012 embedded brains GmbH.  All rights reserved.
 *
 *  embedded brains GmbH
 *  Obere Lagerstr. 30
 *  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.h>
#include <rtems/clockdrv.h>

#include <libcpu/powerpc-utility.h>
#include <bsp/vectors.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.
 */
extern uint32_t bsp_time_base_frequency;

#define PPC_CLOCK_DECREMENTER_MAX UINT32_MAX

volatile uint32_t Clock_driver_ticks = 0;

rtems_device_major_number rtems_clock_major = UINT32_MAX;

rtems_device_minor_number rtems_clock_minor = UINT32_MAX;

static uint32_t ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;

static uint32_t ppc_clock_next_time_base;

static uint64_t ppc_clock_factor;

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

static void (*ppc_clock_tick)(void) = ppc_clock_no_tick;

static int ppc_clock_exception_handler( BSP_Exception_frame *frame, unsigned number)
{
        uint32_t delta = ppc_clock_decrementer_value;
        uint32_t next = ppc_clock_next_time_base;
        uint32_t dec = 0;
        uint32_t now = 0;
        uint32_t msr = 0;

        do {
                /* 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);

                /* Next time base */
                next += delta;

                /* Current time */
                now = ppc_time_base();

                /* New decrementer value */
                dec = next - now;
        } while (dec > delta);

        /* Set decrementer */
        ppc_set_decrementer_register( dec);

        /* Expected next time base */
        ppc_clock_next_time_base = next;

        return 0;
}

static int ppc_clock_exception_handler_first( BSP_Exception_frame *frame, unsigned number)
{
        /* We have to clear the first pending decrementer exception this way */

        if (ppc_decrementer_register() >= 0x80000000) {
                ppc_clock_exception_handler( frame, number);
        }

        ppc_exc_set_handler( ASM_DEC_VECTOR, ppc_clock_exception_handler);

        return 0;
}

static 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;
}

static 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;
}

static uint32_t ppc_clock_nanoseconds_since_last_tick(void)
{
        uint64_t k = ppc_clock_factor;
        uint32_t c = ppc_decrementer_register();
        uint32_t i = ppc_clock_decrementer_value + 1;

        return (uint32_t) (((i - c) * k) >> 32);
}

void Clock_exit(void)
{
        /* 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)
{
        uint64_t frequency = bsp_time_base_frequency;
        uint64_t us_per_tick = rtems_configuration_get_microseconds_per_tick();
        uint32_t interval = (uint32_t) ((frequency * us_per_tick) / 1000000);

        /* 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 (*)(void)) rtems_clock_tick;

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

        /* Factor for nano seconds extension */
        ppc_clock_factor = (1000000000ULL << 32) / frequency;

        /* Decrementer value */
        ppc_clock_decrementer_value = interval - 1;

        /* Check decrementer value */
        if (ppc_clock_decrementer_value == 0) {
                ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;
                RTEMS_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_first);
        }

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

        return RTEMS_SUCCESSFUL;
}