systimer: add HAL layer

components/esp_timer/src/esp_timer_impl_systimer.c

@@ -1,4 +1,4 @@
-// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
+// Copyright 2017-2020 Espressif Systems (Shanghai) PTE LTD
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,63 +12,30 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include <sys/param.h>
 #include "esp_timer_impl.h"
 #include "esp_err.h"
 #include "esp_timer.h"
 #include "esp_attr.h"
 #include "esp_intr_alloc.h"
 #include "esp_log.h"
-#include "soc/rtc.h"
-#include "soc/systimer_reg.h"
 #include "soc/periph_defs.h"
 #include "freertos/FreeRTOS.h"
+#include "hal/systimer_ll.h"
+#include "hal/systimer_types.h"
+#include "hal/systimer_hal.h"
 
 /**
  * @file esp_timer_systimer.c
- * @brief Implementation of chip-specific part of esp_timer
+ * @brief Implementation of esp_timer using systimer.
  *
- * This implementation uses SYSTIMER of the ESP32-S2. This timer is
+ * This timer is a 64-bit up-counting timer, with a programmable compare value (called 'alarm' hereafter).
- * a 64-bit up-counting timer, with a programmable compare value (called 'alarm'
+ * When the timer reaches compare value, interrupt is raised.
- * hereafter). When the timer reaches compare value, interrupt is raised.
+ * The timer can be configured to produce an edge interrupt.
- * The timer can be configured to produce an edge or a level interrupt.
+ *
+ * @note systimer counter0 and alarm2 are adopted to implemented esp_timer
  */
 
-/* esp_timer uses the 2 compare unit of SYSTIMER. */
+static const char *TAG = "esp_timer_systimer";
-#define INTR_SOURCE_LACT                 (ETS_SYSTIMER_TARGET2_EDGE_INTR_SOURCE)
-// Registers
-#define COUNT_LO_REG                     (SYSTIMER_VALUE_LO_REG)
-#define COUNT_HI_REG                     (SYSTIMER_VALUE_HI_REG)
-#define LOAD_LO_REG                      (SYSTIMER_LOAD_LO_REG)
-#define LOAD_HI_REG                      (SYSTIMER_LOAD_HI_REG)
-#define ALARM_LO_REG                     (SYSTIMER_TARGET2_LO_REG)
-#define ALARM_HI_REG                     (SYSTIMER_TARGET2_HI_REG)
-// Macros
-#define ENABLE_CLK()                     (REG_SET_BIT(SYSTIMER_CONF_REG, SYSTIMER_CLK_EN))
-#define ENABLE_INT()                     (REG_SET_BIT(SYSTIMER_INT_ENA_REG, SYSTIMER_INT2_ENA))
-#define DISABLE_INT()                    (REG_CLR_BIT(SYSTIMER_INT_ENA_REG, SYSTIMER_INT2_ENA))
-#define GET_INT_FLAG()                   (REG_GET_FIELD(SYSTIMER_INT_RAW_REG, SYSTIMER_INT2_RAW))
-#define CLEAR_INT()                      (REG_WRITE(SYSTIMER_INT_CLR_REG, SYSTIMER_INT2_CLR))
-#define DISABLE_COMPARE_UNIT()           (REG_WRITE(SYSTIMER_TARGET2_CONF_REG, 0))
-#define ENABLE_COMPARE_UNIT()            (REG_WRITE(SYSTIMER_TARGET2_CONF_REG, SYSTIMER_TARGET2_WORK_EN))
-#define APPLY_LOADED_VAL()               (REG_SET_BIT(SYSTIMER_LOAD_REG, SYSTIMER_TIMER_LOAD))
-#define SETTING_STEP_FOR_PLL_SRC(step)   (REG_SET_FIELD(SYSTIMER_STEP_REG, SYSTIMER_TIMER_PLL_STEP, step))
-#define SETTING_STEP_FOR_XTAL_SRC(step)  (REG_SET_FIELD(SYSTIMER_STEP_REG, SYSTIMER_TIMER_XTAL_STEP, step))
-#define UPDATE_COUNT_REG()               (REG_WRITE(SYSTIMER_UPDATE_REG, SYSTIMER_TIMER_UPDATE))
-#define GET_FLAG_UPDATED_COUNT_REG()     (REG_GET_BIT(SYSTIMER_UPDATE_REG, SYSTIMER_TIMER_VALUE_VALID))
-
-/* Helper type to convert between a 64-bit value and a pair of 32-bit values without shifts and masks */
-typedef struct {
-    union {
-        struct {
-            uint32_t lo;
-            uint32_t hi;
-        };
-        uint64_t val;
-    };
-} timer_64b_reg_t;
-
-static const char* TAG = "esp_timer_impl";
 
 /* Interrupt handle returned by the interrupt allocator */
 static intr_handle_t s_timer_interrupt_handle;
@@ -78,13 +45,9 @@ static intr_handle_t s_timer_interrupt_handle;
  */
 static intr_handler_t s_alarm_handler;
 
-/* Number of timer ticks per microsecond. */
-#define TICKS_PER_US    (APB_CLK_FREQ / 1000000)
-
 /* Spinlock used to protect access to the hardware registers. */
 portMUX_TYPE s_time_update_lock = portMUX_INITIALIZER_UNLOCKED;
 
-
 void esp_timer_impl_lock(void)
 {
     portENTER_CRITICAL(&s_time_update_lock);
@@ -97,134 +60,89 @@ void esp_timer_impl_unlock(void)
 
 uint64_t IRAM_ATTR esp_timer_impl_get_counter_reg(void)
 {
-    uint32_t lo, lo_start, hi;
+    return systimer_hal_get_counter_value(SYSTIMER_COUNTER_0);
-    /* Set the "update" bit and wait for acknowledgment */
-    UPDATE_COUNT_REG();
-    while (GET_FLAG_UPDATED_COUNT_REG() == 0) {
-        ;
-    }
-    /* Read LO, HI, then LO again, check that LO returns the same value.
-     * This accounts for the case when an interrupt may happen between reading
-     * HI and LO values, and this function may get called from the ISR.
-     * In this case, the repeated read will return consistent values.
-     */
-    lo_start = REG_READ(COUNT_LO_REG);
-    do {
-        lo = lo_start;
-        hi = REG_READ(COUNT_HI_REG);
-        lo_start = REG_READ(COUNT_LO_REG);
-    } while (lo_start != lo);
-
-    timer_64b_reg_t result = {
-        .lo = lo,
-        .hi = hi
-    };
-    return result.val;
 }
 
 uint64_t IRAM_ATTR esp_timer_impl_get_time(void)
 {
-    return esp_timer_impl_get_counter_reg() / TICKS_PER_US;
+    return systimer_hal_get_time(SYSTIMER_COUNTER_0);
 }
 
 void IRAM_ATTR esp_timer_impl_set_alarm(uint64_t timestamp)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);
-    int64_t offset = TICKS_PER_US * 2;
+    systimer_hal_set_alarm_value(SYSTIMER_ALARM_2, timestamp);
-    uint64_t now_time = esp_timer_impl_get_counter_reg();
-    timer_64b_reg_t alarm = { .val = MAX(timestamp * TICKS_PER_US, now_time + offset) };
-    do {
-        DISABLE_COMPARE_UNIT();
-        REG_WRITE(ALARM_LO_REG, alarm.lo);
-        REG_WRITE(ALARM_HI_REG, alarm.hi);
-        ENABLE_COMPARE_UNIT();
-        now_time = esp_timer_impl_get_counter_reg();
-        int64_t delta = (int64_t)alarm.val - (int64_t)now_time;
-        if (delta <= 0 && GET_INT_FLAG() == 0) {
-            // new alarm is less than the counter and the interrupt flag is not set
-            offset += abs((int)delta) + TICKS_PER_US * 2;
-            alarm.val = now_time + offset;
-        } else {
-            // finish if either (alarm > counter) or the interrupt flag is already set.
-            break;
-        }
-    } while(1);
     portEXIT_CRITICAL_SAFE(&s_time_update_lock);
 }
 
 static void IRAM_ATTR timer_alarm_isr(void *arg)
 {
     // clear the interrupt
-    CLEAR_INT();
+    systimer_ll_clear_alarm_int(SYSTIMER_ALARM_2);
     /* Call the upper layer handler */
     (*s_alarm_handler)(arg);
 }
 
 void IRAM_ATTR esp_timer_impl_update_apb_freq(uint32_t apb_ticks_per_us)
 {
-    /* If this function was called when switching APB clock to PLL, don't need
+    systimer_hal_on_apb_freq_update(apb_ticks_per_us);
-     * do anything: the SYSTIMER_TIMER_PLL_STEP is already correct.
-     * If this was called when switching APB clock to XTAL, need to adjust
-     * XTAL_STEP value accordingly.
-     */
-    if (apb_ticks_per_us != TICKS_PER_US) {
-        assert((TICKS_PER_US % apb_ticks_per_us) == 0 && "TICK_PER_US should be divisible by APB frequency (in MHz)");
-        SETTING_STEP_FOR_XTAL_SRC(TICKS_PER_US / apb_ticks_per_us);
-    }
 }
 
 void esp_timer_impl_advance(int64_t time_us)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);
-    timer_64b_reg_t new_count = { .val = esp_timer_impl_get_counter_reg() + time_us * TICKS_PER_US };
+    systimer_hal_counter_value_advance(SYSTIMER_COUNTER_0, time_us);
-    REG_WRITE(LOAD_LO_REG, new_count.lo);
-    REG_WRITE(LOAD_HI_REG, new_count.hi);
-    APPLY_LOADED_VAL();
     portEXIT_CRITICAL_SAFE(&s_time_update_lock);
 }
 
 esp_err_t esp_timer_impl_init(intr_handler_t alarm_handler)
 {
     s_alarm_handler = alarm_handler;
-
+    esp_err_t err = esp_intr_alloc(ETS_SYSTIMER_TARGET2_EDGE_INTR_SOURCE,
-    esp_err_t err = esp_intr_alloc(INTR_SOURCE_LACT,
                                    ESP_INTR_FLAG_INTRDISABLED | ESP_INTR_FLAG_IRAM | ESP_INTR_FLAG_EDGE,
                                    &timer_alarm_isr, NULL, &s_timer_interrupt_handle);
 
     if (err != ESP_OK) {
-        ESP_EARLY_LOGE(TAG, "esp_intr_alloc failed (0x%0x)", err);
+        ESP_EARLY_LOGE(TAG, "esp_intr_alloc failed (%#x)", err);
-        return err;
+        goto err_intr_alloc;
     }
-    ENABLE_CLK();
+
-    /* Configure the counter:
+    systimer_hal_enable_counter(SYSTIMER_COUNTER_0);
-     * - increment by 1 when running from PLL (80 ticks per microsecond),
+    systimer_hal_init();
-     * - increment by 2 when running from XTAL (40 ticks per microsecond).
+    systimer_hal_select_alarm_mode(SYSTIMER_ALARM_2, SYSTIMER_ALARM_MODE_ONESHOT);
-     * Note that if the APB frequency is derived from XTAL with divider != 1,
+
-     * XTAL_STEP needs to be adjusted accordingly. For example, if
-     * the APB frequency is XTAL/4 = 10 MHz, then XTAL_STEP should be set to 8.
-     * This is handled in esp_timer_impl_update_apb_freq function above.
-     */
-    assert(rtc_clk_xtal_freq_get() == 40 && TICKS_PER_US == 80
-        && "update the following code to support other XTAL:APB frequency ratios");
-    SETTING_STEP_FOR_PLL_SRC(1);
-    SETTING_STEP_FOR_XTAL_SRC(2);
     /* TODO: if SYSTIMER is used for anything else, access to SYSTIMER_INT_ENA_REG has to be
     * protected by a shared spinlock. Since this code runs as part of early startup, this
-     * is practically not an issue. Same applies to SYSTIMER_CLK_EN above.
+    * is practically not an issue.
     */
-    ENABLE_INT();
+    systimer_hal_enable_alarm_int(SYSTIMER_ALARM_2);
-    ESP_ERROR_CHECK(esp_intr_enable(s_timer_interrupt_handle));
+
+    err = esp_intr_enable(s_timer_interrupt_handle);
+    if (err != ESP_OK) {
+        ESP_EARLY_LOGE(TAG, "esp_intr_enable failed (%#x)", err);
+        goto err_intr_en;
+    }
     return ESP_OK;
+
+err_intr_en:
+    systimer_ll_disable_alarm(SYSTIMER_ALARM_2);
+    /* TODO: may need a spinlock, see the note related to SYSTIMER_INT_ENA_REG in systimer_hal_init */
+    systimer_ll_disable_alarm_int(SYSTIMER_ALARM_2);
+    esp_intr_free(s_timer_interrupt_handle);
+err_intr_alloc:
+    s_alarm_handler = NULL;
+    return err;
 }
 
 void esp_timer_impl_deinit(void)
 {
     esp_intr_disable(s_timer_interrupt_handle);
-    DISABLE_COMPARE_UNIT();
+    systimer_ll_disable_alarm(SYSTIMER_ALARM_2);
-    /* TODO: may need a spinlock, see the note related to SYSTIMER_INT_ENA_REG in esp_timer_impl_init */
+    /* TODO: may need a spinlock, see the note related to SYSTIMER_INT_ENA_REG in systimer_hal_init */
-    DISABLE_INT();
+    systimer_ll_disable_alarm_int(SYSTIMER_ALARM_2);
     esp_intr_free(s_timer_interrupt_handle);
     s_timer_interrupt_handle = NULL;
+    s_alarm_handler = NULL;
 }
 
 uint64_t IRAM_ATTR esp_timer_impl_get_min_period_us(void)
@@ -235,12 +153,9 @@ uint64_t IRAM_ATTR esp_timer_impl_get_min_period_us(void)
 uint64_t esp_timer_impl_get_alarm_reg(void)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);
-    timer_64b_reg_t alarm = {
+    uint64_t val = systimer_hal_get_alarm_value(SYSTIMER_ALARM_2);
-        .lo = REG_READ(ALARM_LO_REG),
-        .hi = REG_READ(ALARM_HI_REG)
-    };
     portEXIT_CRITICAL_SAFE(&s_time_update_lock);
-    return alarm.val;
+    return val;
 }
 
 void esp_timer_private_update_apb_freq(uint32_t apb_ticks_per_us) __attribute__((alias("esp_timer_impl_update_apb_freq")));

components/soc/include/hal/systimer_hal.h

@@ -0,0 +1,76 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include "hal/systimer_types.h"
+
+/**
+ * @brief enable systimer counter
+ */
+void systimer_hal_enable_counter(systimer_counter_id_t counter_id);
+
+/**
+ * @brief get current counter value
+ */
+uint64_t systimer_hal_get_counter_value(systimer_counter_id_t counter_id);
+
+/**
+ * @brief get current time (in microseconds)
+ */
+uint64_t systimer_hal_get_time(systimer_counter_id_t counter_id);
+
+/**
+ * @brief set alarm time
+ */
+void systimer_hal_set_alarm_value(systimer_alarm_id_t alarm_id, uint64_t timestamp);
+
+/**
+ * @brief get alarm time
+ */
+uint64_t systimer_hal_get_alarm_value(systimer_alarm_id_t alarm_id);
+
+/**
+ * @brief enable alarm interrupt
+ */
+void systimer_hal_enable_alarm_int(systimer_alarm_id_t alarm_id);
+
+/**
+ * @brief select alarm mode
+ */
+void systimer_hal_select_alarm_mode(systimer_alarm_id_t alarm_id, systimer_alarm_mode_t mode);
+
+/**
+ * @brief update systimer step when apb clock gets changed
+ */
+void systimer_hal_on_apb_freq_update(uint32_t apb_ticks_per_us);
+
+/**
+ * @brief move systimer counter value forward or backward
+ */
+void systimer_hal_counter_value_advance(systimer_counter_id_t counter_id, int64_t time_us);
+
+/**
+ * @brief initialize systimer in HAL layer
+ */
+void systimer_hal_init(void);
+
+#ifdef __cplusplus
+}
+#endif

components/soc/include/hal/systimer_types.h

@@ -0,0 +1,74 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include "soc/systimer_caps.h"
+
+/*
+ * @brief The structure of the counter value in systimer
+ *
+ */
+typedef struct {
+    union {
+        struct {
+            uint64_t lo : SOC_SYSTIMER_BIT_WIDTH_LO; /*!< Low part of counter value */
+            uint64_t hi : SOC_SYSTIMER_BIT_WIDTH_HI; /*!< High part of counter value */
+        };
+        uint64_t val; /*!< counter value */
+    };
+} systimer_counter_value_t;
+
+/** @cond */
+_Static_assert(sizeof(systimer_counter_value_t) == 8, "systimer_counter_value_t should occupy 8 bytes in memory");
+/** @endcond */
+
+/**
+ * @brief systimer counter ID
+ *
+ */
+typedef enum {
+    SYSTIMER_COUNTER_0, /*!< systimer counter 0 */
+#if SOC_SYSTIMER_COUNTER_NUM > 1
+    SYSTIEMR_COUNTER_1, /*!< systimer counter 1 */
+#endif
+} systimer_counter_id_t;
+
+/**
+ * @brief systimer alarm ID
+ *
+ */
+typedef enum {
+    SYSTIMER_ALARM_0, /*!< systimer alarm 0 */
+    SYSTIMER_ALARM_1, /*!< systimer alarm 1 */
+    SYSTIMER_ALARM_2, /*!< systimer alarm 2 */
+} systimer_alarm_id_t;
+
+/**
+ * @brief systimer alarm mode
+ *
+ */
+typedef enum {
+    SYSTIMER_ALARM_MODE_ONESHOT, /*!< systimer alarm oneshot mode */
+    SYSTIMER_ALARM_MODE_PERIOD,  /*!< systimer alarm period mode */
+} systimer_alarm_mode_t;
+
+#ifdef __cplusplus
+}
+#endif

components/soc/linker.lf

@@ -24,3 +24,4 @@ entries:
     cpu_hal (noflash)
     soc_hal (noflash)
     wdt_hal_iram (noflash)
+    systimer_hal (noflash)

components/soc/soc/esp32s2/include/soc/systimer_caps.h

@@ -0,0 +1,21 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#define SOC_SYSTIMER_COUNTER_NUM (1)   // Number of counter units
+#define SOC_SYSTIMER_ALARM_NUM (3)     // Number of alarm units
+
+#define SOC_SYSTIMER_BIT_WIDTH_LO (32) // Bit width of systimer low part
+#define SOC_SYSTIMER_BIT_WIDTH_HI (32) // Bit width of systimer high part

components/soc/src/esp32s2/CMakeLists.txt

@@ -6,6 +6,7 @@ set(srcs "brownout_hal.c"
         "rtc_sleep.c"
         "rtc_time.c"
         "soc_memory_layout.c"
+        "systimer_hal.c"
         "touch_sensor_hal.c"
         "usb_hal.c")
 

components/soc/src/esp32s2/include/hal/systimer_ll.h

@@ -0,0 +1,138 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "soc/soc.h"
+#include "soc/systimer_reg.h"
+
+// All these functions get invoked either from ISR or HAL that linked to IRAM.
+// Always inline these functions even no gcc optimization is applied.
+
+/*******************counter*************************/
+
+__attribute__((always_inline)) static inline void systimer_ll_enable_clock(void)
+{
+    REG_SET_BIT(SYSTIMER_CONF_REG, SYSTIMER_CLK_EN);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_apply_counter_value(void)
+{
+    REG_SET_BIT(SYSTIMER_LOAD_REG, SYSTIMER_TIMER_LOAD);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_load_counter_value(uint64_t value)
+{
+    REG_WRITE(SYSTIMER_LOAD_LO_REG, value & 0xFFFFFFFF);
+    REG_WRITE(SYSTIMER_LOAD_HI_REG, (value & 0xFFFFFFFF00000000) >> 32);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_set_step_for_pll(uint32_t step)
+{
+    REG_SET_FIELD(SYSTIMER_STEP_REG, SYSTIMER_TIMER_PLL_STEP, step);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_set_step_for_xtal(uint32_t step)
+{
+    REG_SET_FIELD(SYSTIMER_STEP_REG, SYSTIMER_TIMER_XTAL_STEP, step);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_counter_snapshot(void)
+{
+    REG_WRITE(SYSTIMER_UPDATE_REG, SYSTIMER_TIMER_UPDATE);
+}
+
+__attribute__((always_inline)) static inline bool systimer_ll_is_counter_value_valid(void)
+{
+    return REG_GET_BIT(SYSTIMER_UPDATE_REG, SYSTIMER_TIMER_VALUE_VALID);
+}
+
+__attribute__((always_inline)) static inline uint32_t systimer_ll_get_counter_value_low(void)
+{
+    return REG_READ(SYSTIMER_VALUE_LO_REG);
+}
+
+__attribute__((always_inline)) static inline uint32_t systimer_ll_get_counter_value_high(void)
+{
+    return REG_READ(SYSTIMER_VALUE_HI_REG);
+}
+
+/*******************alarm*************************/
+
+__attribute__((always_inline)) static inline void systimer_ll_set_alarm_value(uint32_t alarm_id, uint64_t value)
+{
+    REG_WRITE(SYSTIMER_TARGET0_LO_REG + alarm_id * 8, value & 0xFFFFFFFF);
+    REG_WRITE(SYSTIMER_TARGET0_HI_REG + alarm_id * 8, (value & 0xFFFFFFFF00000000) >> 32);
+}
+
+__attribute__((always_inline)) static inline uint64_t systimer_ll_get_alarm_value(uint32_t alarm_id)
+{
+    return (uint64_t)REG_READ(SYSTIMER_TARGET0_HI_REG + alarm_id * 8) << 32 | REG_READ(SYSTIMER_TARGET0_LO_REG + alarm_id * 8);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_enable_alarm(uint32_t alarm_id)
+{
+    REG_SET_BIT(SYSTIMER_TARGET0_CONF_REG + alarm_id * 4, BIT(31));
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_disable_alarm(uint32_t alarm_id)
+{
+    REG_CLR_BIT(SYSTIMER_TARGET0_CONF_REG + alarm_id * 4, BIT(31));
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_enable_alarm_oneshot(uint32_t alarm_id)
+{
+    REG_CLR_BIT(SYSTIMER_TARGET0_CONF_REG + alarm_id * 4, BIT(30));
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_enable_alarm_period(uint32_t alarm_id)
+{
+    REG_SET_BIT(SYSTIMER_TARGET0_CONF_REG + alarm_id * 4, BIT(30));
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_set_alarm_period(uint32_t alarm_id, uint32_t period)
+{
+    REG_SET_FIELD(SYSTIMER_TARGET0_CONF_REG + alarm_id * 4, SYSTIMER_TARGET0_PERIOD, period);
+}
+
+/*******************interrupt*************************/
+
+__attribute__((always_inline)) static inline void systimer_ll_enable_alarm_int(uint32_t alarm_id)
+{
+    REG_SET_BIT(SYSTIMER_INT_ENA_REG, 1 << alarm_id);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_disable_alarm_int(uint32_t alarm_id)
+{
+    REG_CLR_BIT(SYSTIMER_INT_ENA_REG, 1 << alarm_id);
+}
+
+__attribute__((always_inline)) static inline bool systimer_ll_is_alarm_int_fired(uint32_t alarm_id)
+{
+    return REG_GET_BIT(SYSTIMER_INT_RAW_REG, 1 << alarm_id);
+}
+
+__attribute__((always_inline)) static inline void systimer_ll_clear_alarm_int(uint32_t alarm_id)
+{
+    REG_SET_BIT(SYSTIMER_INT_CLR_REG, 1 << alarm_id);
+}
+
+#ifdef __cplusplus
+}
+#endif

components/soc/src/esp32s2/systimer_hal.c

@@ -0,0 +1,140 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/param.h>
+#include <assert.h>
+#include "hal/systimer_hal.h"
+#include "hal/systimer_ll.h"
+#include "hal/systimer_types.h"
+#include "soc/systimer_caps.h"
+#include "soc/rtc.h"
+
+#define SYSTIMER_TICKS_PER_US (80) // Number of timer ticks per microsecond
+
+uint64_t systimer_hal_get_counter_value(systimer_counter_id_t counter_id)
+{
+    uint32_t lo, lo_start, hi;
+    /* Set the "update" bit and wait for acknowledgment */
+    systimer_ll_counter_snapshot();
+    while (!systimer_ll_is_counter_value_valid());
+    /* Read LO, HI, then LO again, check that LO returns the same value.
+     * This accounts for the case when an interrupt may happen between reading
+     * HI and LO values, and this function may get called from the ISR.
+     * In this case, the repeated read will return consistent values.
+     */
+    lo_start = systimer_ll_get_counter_value_low();
+    do {
+        lo = lo_start;
+        hi = systimer_ll_get_counter_value_high();
+        lo_start = systimer_ll_get_counter_value_low();
+    } while (lo_start != lo);
+
+    systimer_counter_value_t result = {
+        .lo = lo,
+        .hi = hi
+    };
+
+    return result.val;
+}
+
+uint64_t systimer_hal_get_time(systimer_counter_id_t counter_id)
+{
+    return systimer_hal_get_counter_value(counter_id) / SYSTIMER_TICKS_PER_US;
+}
+
+void systimer_hal_set_alarm_value(systimer_alarm_id_t alarm_id, uint64_t timestamp)
+{
+    int64_t offset = SYSTIMER_TICKS_PER_US * 2;
+    uint64_t now_time = systimer_hal_get_counter_value(SYSTIMER_COUNTER_0);
+    systimer_counter_value_t alarm = { .val = MAX(timestamp * SYSTIMER_TICKS_PER_US, now_time + offset) };
+    do {
+        systimer_ll_disable_alarm(alarm_id);
+        systimer_ll_set_alarm_value(alarm_id, alarm.val);
+        systimer_ll_enable_alarm(alarm_id);
+        now_time = systimer_hal_get_counter_value(SYSTIMER_COUNTER_0);
+        int64_t delta = (int64_t)alarm.val - (int64_t)now_time;
+        if (delta <= 0 && !systimer_ll_is_alarm_int_fired(alarm_id)) {
+            // new alarm is less than the counter and the interrupt flag is not set
+            offset += -1 * delta + SYSTIMER_TICKS_PER_US * 2;
+            alarm.val = now_time + offset;
+        } else {
+            // finish if either (alarm > counter) or the interrupt flag is already set.
+            break;
+        }
+    } while (1);
+}
+
+uint64_t systimer_hal_get_alarm_value(systimer_alarm_id_t alarm_id)
+{
+    return systimer_ll_get_alarm_value(alarm_id);
+}
+
+void systimer_hal_enable_alarm_int(systimer_alarm_id_t alarm_id)
+{
+    systimer_ll_enable_alarm_int(alarm_id);
+}
+
+void systimer_hal_on_apb_freq_update(uint32_t apb_ticks_per_us)
+{
+    /* If this function was called when switching APB clock to PLL, don't need
+     * do anything: the SYSTIMER_TIMER_PLL_STEP is already correct.
+     * If this was called when switching APB clock to XTAL, need to adjust
+     * XTAL_STEP value accordingly.
+     */
+    if (apb_ticks_per_us != SYSTIMER_TICKS_PER_US) {
+        assert((SYSTIMER_TICKS_PER_US % apb_ticks_per_us) == 0 && "TICK_PER_US should be divisible by APB frequency (in MHz)");
+        systimer_ll_set_step_for_xtal(SYSTIMER_TICKS_PER_US / apb_ticks_per_us);
+    }
+}
+
+void systimer_hal_counter_value_advance(systimer_counter_id_t counter_id, int64_t time_us)
+{
+    systimer_counter_value_t new_count = { .val = systimer_hal_get_counter_value(counter_id) + time_us * SYSTIMER_TICKS_PER_US };
+    systimer_ll_load_counter_value(new_count.val);
+    systimer_ll_apply_counter_value();
+}
+
+void systimer_hal_enable_counter(systimer_counter_id_t counter_id)
+{
+    systimer_ll_enable_clock();
+}
+
+void systimer_hal_init(void)
+{
+    assert(rtc_clk_xtal_freq_get() == 40 && "update the step for xtal to support other XTAL:APB frequency ratios");
+    /* Configure the counter:
+     * - increment by 1 when running from PLL (80 ticks per microsecond),
+     * - increment by 2 when running from XTAL (40 ticks per microsecond).
+     * Note that if the APB frequency is derived from XTAL with divider != 1,
+     * XTAL_STEP needs to be adjusted accordingly. For example, if
+     * the APB frequency is XTAL/4 = 10 MHz, then XTAL_STEP should be set to 8.
+     * This is handled in systimer_hal_on_apb_freq_update function.
+     */
+    systimer_ll_set_step_for_pll(1);
+    systimer_ll_set_step_for_xtal(2);
+}
+
+void systimer_hal_select_alarm_mode(systimer_alarm_id_t alarm_id, systimer_alarm_mode_t mode)
+{
+    switch (mode) {
+    case SYSTIMER_ALARM_MODE_ONESHOT:
+        systimer_ll_enable_alarm_oneshot(alarm_id);
+        break;
+    case SYSTIMER_ALARM_MODE_PERIOD:
+        systimer_ll_enable_alarm_period(alarm_id);
+        break;
+    default:
+        break;
+    }
+}