esp-idf/components/freertos/test/test_fpu_in_isr.c

/*
 * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include "sdkconfig.h"
#include <math.h>
#include "soc/soc_caps.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "unity.h"
#include "test_utils.h"

#if SOC_CPU_HAS_FPU && CONFIG_FREERTOS_FPU_IN_ISR

// We can use xtensa API here as currently, non of the RISC-V targets have an FPU
#include "xtensa/xtensa_api.h"
#include "esp_intr_alloc.h"

#define SW_ISR_LEVEL_1      7

static void fpu_isr(void *arg)
{
    // Clear the interrupt
    xt_set_intclear(1 << SW_ISR_LEVEL_1);
    /*
    Use the FPU
    - We test using a calculation that will cause a change in mantissa and exponent for extra thoroughness
    - cosf(0.0f) should return 1.0f, thus we are simply doubling test_float every iteration.
    - Therefore, we should end up with (0.01) * (2^8) = 2.56 at the end of the loop
    */
    volatile float test_float = 0.01f;
    for (int i = 0; i < 8; i++) {
        test_float = test_float * 2.0f * cosf(0.0f);
    }
    // We allow a 0.1% delta on the final result in case of any loss of precision from floating point calculations
    TEST_ASSERT_FLOAT_WITHIN(0.00256f, 2.56f, test_float);
}

/* ------------------------------------------------------------------------------------------------------------------ */

/*
Test FPU usage from a level 1 ISR

Purpose:
    - Test that the FPU can be used from a level 1 ISR
    - Test that the ISR using the FPU does not corrupt the interrupted task's FPU context
Procedure:
    - Allocate a level 1 ISR
    - Task uses the FPU then triggers the ISR
    - ISR uses the FPU as well (forcing the task's FPU context to be saved)
    - Task continues using the FPU (forcing its FPU context to be restored)
Expected:
    - ISR should use the FPU without issue
    - The interrupted task can continue using the FPU without issue
*/

TEST_CASE("FPU: Usage in level 1 ISR", "[freertos]")
{
    intr_handle_t isr_handle;
    TEST_ASSERT_EQUAL(ESP_OK, esp_intr_alloc(ETS_INTERNAL_SW0_INTR_SOURCE, ESP_INTR_FLAG_LEVEL1, &fpu_isr, NULL, &isr_handle));
    /*
    Use the FPU (calculate a different value than in the ISR)
    - We test using a calculation that will cause a change in mantissa and exponent for extra thoroughness
    - cosf(0.0f) should return 1.0f, thus we are simply dividing test_float every iteration.
    */
    // We should end up with (2.56) / (2^4) = 0.16 at the end of the first loop
    volatile float test_float = 2.56f;
    for (int i = 0; i < 4; i++) {
        test_float = test_float / (2.0f * cosf(0.0f));
    }
    // We allow a 0.1% delta on the final result in case of any loss of precision from floating point calculations
    TEST_ASSERT_FLOAT_WITHIN(0.00016f, 0.16f, test_float);

    // Trigger the ISR
    xt_set_intset(1 << SW_ISR_LEVEL_1);

    // Continue using the FPU from a task context after the interrupt returns
    // We should end up with (0.16) / (2^4) = 0.01 at the end of the first loop
    for (int i = 0; i < 4; i++) {
        test_float = test_float / (2.0f * cosf(0.0f));
    }
    // We allow a 0.1% delta on the final result in case of any loss of precision from floating point calculations
    TEST_ASSERT_FLOAT_WITHIN(0.00001f, 0.01f, test_float);

    // Free the ISR
    esp_intr_free(isr_handle);
}

/* ------------------------------------------------------------------------------------------------------------------ */

/*
Test FPU usage in ISR does not affect an unpinned tasks

Purpose:
    - Test that the ISR using the FPU will not affect the interrupted task's affinity
Procedure:
    - Create an unpinned task
    - Unpinned task disables scheduling/preemption to ensure that it does not switch cores
    - Unpinned task allocates an ISR then triggers the ISR
    - The ISR interrupts the unpinned task then uses the FPU
    - Task reenables scheduling/preemption and cleans up
Expected:
    - The ISR using the FPU will not affect the unpinned task's affinity
*/

static void unpinned_task(void *arg)
{
    // Disable scheduling to make sure the current task doesn't switch cores
    vTaskSuspendAll();

    // Check that the task is unpinned
    TEST_ASSERT_EQUAL(tskNO_AFFINITY, xTaskGetAffinity(NULL));


    // Allocate an ISR to use the FPU
    intr_handle_t isr_handle;
    TEST_ASSERT_EQUAL(ESP_OK, esp_intr_alloc(ETS_INTERNAL_SW0_INTR_SOURCE, ESP_INTR_FLAG_LEVEL1, &fpu_isr, NULL, &isr_handle));
    // Trigger the ISR
    xt_set_intset(1 << SW_ISR_LEVEL_1);
    // Free the ISR
    esp_intr_free(isr_handle);

    // Task should remain unpinned after the ISR uses the FPU
    TEST_ASSERT_EQUAL(tskNO_AFFINITY, xTaskGetAffinity(NULL));

    // Reenable scheduling
    xTaskResumeAll();

    // Indicate done and self delete
    xTaskNotifyGive((TaskHandle_t)arg);
    vTaskDelete(NULL);
}

TEST_CASE("FPU: Level 1 ISR does not affect unpinned task", "[freertos]")
{
    TaskHandle_t unity_task_handle = xTaskGetCurrentTaskHandle();
    xTaskCreate(unpinned_task, "unpin", 2048, (void *)unity_task_handle, UNITY_FREERTOS_PRIORITY + 1, NULL);
    // Wait for task to complete
    ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
    vTaskDelay(10); // Short delay to allow task memory to be freed
}

#endif // SOC_CPU_HAS_FPU && CONFIG_FREERTOS_FPU_IN_ISR