freertos_port.c

// Copyright lowRISC contributors (OpenTitan project).
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
 
#include "dt/dt_rv_timer.h"
#include "external/freertos/include/FreeRTOS.h"
#include "external/freertos/include/task.h"
#include "external/freertos/portable/GCC/RISC-V/portmacro.h"
#include "sw/device/lib/base/macros.h"
#include "sw/device/lib/dif/dif_rv_timer.h"
#include "sw/device/lib/runtime/irq.h"
#include "sw/device/lib/runtime/log.h"
#include "sw/device/lib/testing/test_framework/FreeRTOSConfig.h"
#include "sw/device/lib/testing/test_framework/check.h"
 
// NOTE: some of the function names below do NOT, and cannot, conform to the
// style guide, since they are specific implementations of FreeRTOS defined
// functions.
 
// ----------------------------------------------------------------------------
// Heap Setup
//
// We allocate the heap here and mark it so the linker can make a
// NOLOAD section. Otherwise, it will end up in the `.bss` section, which gets
// zeroed during boot initializations which wastes simulation cycles.
// ----------------------------------------------------------------------------
OT_SET_BSS_SECTION(".freertos.heap", uint8_t ucHeap[configTOTAL_HEAP_SIZE];)
 
// ----------------------------------------------------------------------------
// Timer Setup (for use when preemptive scheduling is enabled)
// ----------------------------------------------------------------------------
#if configUSE_PREEMPTION
 
static dif_rv_timer_t timer;
static const uint32_t kTimerHartId = (uint32_t)0;
static const uint32_t kTimerComparatorId = 0;
static const uint64_t kTimerDeadline =
    100;  // Counter must reach 100 for an IRQ to be triggered.
 
// Override the timer ISR to support preemptive context switching.
void ottf_timer_isr(uint32_t *exc_info) {
  LOG_INFO("Handling timer IQR ...");
  dif_rv_timer_irq_enable_snapshot_t irq_enable_snapshot;
  CHECK_DIF_OK(
      dif_rv_timer_irq_disable_all(&timer, kTimerHartId, &irq_enable_snapshot));
  CHECK_DIF_OK(dif_rv_timer_counter_write(&timer, kTimerHartId, 0));
  CHECK_DIF_OK(dif_rv_timer_irq_acknowledge(
      &timer, kDifRvTimerIrqTimerExpiredHart0Timer0));
  // TODO: increment scheduler tick and switch context if necessary
  CHECK_DIF_OK(
      dif_rv_timer_irq_restore_all(&timer, kTimerHartId, &irq_enable_snapshot));
  LOG_INFO("Done.");
}
 
void vPortSetupTimerInterrupt(void) {
  LOG_INFO("Configuring timer interrupt ...");
 
  // Initialize and reset the timer.
  CHECK_DIF_OK(dif_rv_timer_init_from_dt(kDtRvTimer, &timer));
  CHECK_DIF_OK(dif_rv_timer_reset(&timer));
 
  // Compute and set tick parameters (i.e., step, prescale, etc.).
  dif_rv_timer_tick_params_t tick_params;
  CHECK_DIF_OK(dif_rv_timer_approximate_tick_params(
      kClockFreqPeripheralHz, configTICK_RATE_HZ * kTimerDeadline,
      &tick_params));
  LOG_INFO("Tick Freq. (Hz): %u, Prescale: %u; Tick Step: %u",
           (uint32_t)kClockFreqPeripheralHz, (uint32_t)tick_params.prescale,
           (uint32_t)tick_params.tick_step);
  CHECK_DIF_OK(dif_rv_timer_set_tick_params(&timer, kTimerHartId, tick_params));
 
  // Enable RV Timer interrupts and arm/enable the timer.
  CHECK_DIF_OK(dif_rv_timer_irq_set_enabled(
      &timer, kDifRvTimerIrqTimerExpiredHart0Timer0, kDifToggleEnabled));
  CHECK_DIF_OK(dif_rv_timer_arm(&timer, kTimerHartId, kTimerComparatorId,
                                kTimerDeadline));
 
  CHECK_DIF_OK(dif_rv_timer_counter_set_enabled(&timer, kTimerHartId,
                                                kDifToggleEnabled));
}
 
#endif  // configUSE_PREEMPTION
 
// ----------------------------------------------------------------------------
// Scheduler Setup
// ----------------------------------------------------------------------------
extern void xPortStartFirstTask(void);
 
BaseType_t xPortStartScheduler(void) {
#if configUSE_PREEMPTION
  vPortSetupTimerInterrupt();
#endif  // configUSE_PREEMPTION
  irq_timer_ctrl(true);
  irq_external_ctrl(true);
  irq_software_ctrl(true);
  // Note: no need to call 'irq_global_ctrl(true)' since the global interrupt
  // enable is set in the xPortStartFirstTask sub-routine in
  // sw/device/lib/testing/test_framework/freertos_port.S.
  xPortStartFirstTask();
 
  // Unreachable.
  return pdFAIL;
}