Reverse engineered ets_timers.o

Switch from FreeRTOS queue to task notification.
Removed unknown/unused code.

Rename sdk_ets_handler_isr to process_pending_timers
Add function for microseconds
Simplify time to ticks conversion

open_esplibs/include/open_esplibs.h

@@ -39,6 +39,9 @@
 #ifndef OPEN_LIBMAIN_ETS_TIMER
 #define OPEN_LIBMAIN_ETS_TIMER (OPEN_LIBMAIN)
 #endif
+#ifndef OPEN_LIBMAIN_ETS_TIMER
+#define OPEN_LIBMAIN_ETS_TIMER (OPEN_LIBMAIN)
+#endif
 
 #ifndef OPEN_LIBNET80211
 #define OPEN_LIBNET80211 (OPEN_ESPLIBS)

open_esplibs/libmain/ets_timer.c

@@ -0,0 +1,317 @@
+/**
+ * Recreated Espressif libmain ets_timer.o contents.
+ *
+ * Copyright (C) 2015 Espressif Systems. Derived from MIT Licensed SDK libraries.
+ * BSD Licensed as described in the file LICENSE
+ *
+ * Copyright (c) 2016 sheinz (https://github.com/sheinz)
+ *
+ * This module seems to be adapted from NONOS SDK by Espressif to fit into
+ * RTOS SDK. Function sdk_ets_timer_handler_isr is no longer an ISR handler
+ * but still holds its name. Espressif just added a task that receives events
+ * from the real FRC2 timer ISR handler and calls former ISR handler.
+ * So, timer callbacks are called from the task context rather than an interrupt.
+ *
+ * Modifications from the original reverse engineered version:
+ *  - FreeRTOS queue is replaced with Task notifications.
+ *  - Removed unknown queue length monitoring and parameters allocation.
+ *  - Removed unused debug variables
+ *  - xTaskGenericCreate is replaced with xTaskCreate
+ *  - simplified time to ticks conversion (simply multiply by 5)
+ *
+ * This timer should be used with caution together with other tasks. As the
+ * timer callback is executed within timer task context, access to data that
+ * other tasks accessing should be protected.
+ */
+#include "open_esplibs.h"
+
+#if OPEN_LIBMAIN_ETS_TIMER
+
+#include "open_esplibs.h"
+#include <stdint.h>
+#include <stdbool.h>
+#include <esp/timer_regs.h>
+#include <FreeRTOS.h>
+#include <timers.h>
+#include <queue.h>
+#include <stdio.h>
+
+typedef void ets_timer_func_t(void *);
+
+/**
+ * This structure is used for both timers: ets_timer.c and timer.c
+ */
+typedef struct ets_timer_st {
+    struct ets_timer_st  *next;
+    TimerHandle_t timer_handle;  // not used in ets_timer.c
+    uint32_t fire_ticks;         // FRC2 timer value when timer should fire
+    uint32_t period_ticks;       // timer value in FRC2 ticks for rpeating timers
+    ets_timer_func_t *callback;
+    bool repeat;                 // not used in ets_timer.c
+    void *timer_arg;
+} ets_timer_t;
+
+/**
+ * Special values of ets_timer_t::next field
+ */
+#define ETS_TIMER_NOT_ARMED (ets_timer_t*)(0xffffffff)
+#define ETS_TIMER_LIST_END  (ets_timer_t*)(0)
+
+/**
+ * Linked list of timers
+ */
+static ets_timer_t* timer_list = 0;
+
+static TaskHandle_t task_handle = NULL;
+
+void sdk_ets_timer_setfn(ets_timer_t *timer, ets_timer_func_t *func, void *parg)
+{
+    timer->callback = func;
+    timer->timer_arg = parg;
+    timer->fire_ticks = 0;
+    timer->period_ticks = 0;
+    timer->next = ETS_TIMER_NOT_ARMED;
+}
+
+/**
+ * .Lfunc004
+ */
+static inline void set_alarm_value(uint32_t value)
+{
+    TIMER_FRC2.ALARM = value;
+}
+
+/**
+ * .Lfunc005
+ *
+ * Set timer alarm and make sure the alarm is set in the future
+ * and will not be missed by the timer.
+ */
+static void set_alarm(uint32_t ticks)
+{
+    uint32_t curr_time = TIMER_FRC2.COUNT;
+    int32_t delta = (int32_t)ticks - curr_time;
+    if ((delta - 40) < 1) {
+        if (delta < 1) {
+            set_alarm_value(curr_time + 40);
+        } else {
+            set_alarm_value(ticks + 44);
+        }
+    } else {
+        set_alarm_value(ticks);
+    }
+}
+
+/**
+ * .Lfunc006
+ *
+ * Pending timer list example:
+ *
+ * | Timer:      | T0 | T1 | T2 | T3 |
+ * |-------------|----|----|----|----|
+ * | fire_ticks: | 10 | 20 | 30 | 40 |
+ * | next:       | T1 | T2 | T3 | 0  |
+ *
+ *
+ * For example we need to add a timer that should fire at 25 ticks:
+ *
+ * | Timer:      | T0 | T1  | new | T2 | T3 |
+ * |-------------|----|-----|-----|----|----|
+ * | fire_ticks: | 10 | 20  | 25  | 30 | 40 |
+ * | next:       | T1 | new | T2  | T3 | 0  |
+ *
+ * We squeeze the timer into the list so the list will always remain sorted
+ *
+ * Note: if add the same timer twice the system halts
+*/
+static void add_pending_timer(uint32_t ticks, ets_timer_t *timer)
+{
+    ets_timer_t *prev = 0;
+    ets_timer_t *curr = timer_list;
+    while (curr) {
+        if (((int32_t)ticks - (int32_t)curr->fire_ticks) < 1) {
+            // found a timer that should fire later
+            // so our timer should fire earlier
+            break;
+        }
+        prev = curr;
+        curr = curr->next;
+    }
+
+    timer->next = curr;
+    timer->fire_ticks = ticks;
+
+    if (prev != 0) {
+        prev->next = timer;
+    } else {
+        // Our timer is the first in the line to fire
+        timer_list = timer;
+        set_alarm(ticks);
+    }
+
+    // This situation might happen if adding the same timer twice
+    if (timer == timer->next) {
+        // This seems like an error: %s is used for line number
+        // In the recent SDK Espressif fixed the format to "%s %u\n"
+        printf("%s %s \n", "ets_timer.c", (char*)209);
+        while (1);
+    }
+}
+
+/**
+ * In the Espressif SDK 0.9.9 if try to arm already armed timer the system halts
+ * with error message. In the later SDK version Espressif changed the behavior.
+ * If the timer was previously armed it is disarmed and then armed without errors.
+ * This version recreates behavior of SDK 0.9.9
+ */
+void sdk_ets_timer_arm_ms_us(ets_timer_t *timer, uint32_t value,
+        bool repeat_flag, bool value_in_ms)
+{
+    uint32_t ticks = 0;
+
+    if (timer->next != ETS_TIMER_NOT_ARMED) {
+        // The error message doesn't tell what is wrong
+        printf("arm new %x %x\n", (uint32_t)timer, (uint32_t)timer->next);
+        while(1);  // halt
+    }
+
+    if (value_in_ms) {
+        ticks = value * 5000;
+    } else {
+        ticks = value * 5;
+    }
+
+    if (repeat_flag) {
+        timer->period_ticks = ticks;
+    }
+    vPortEnterCritical();
+    add_pending_timer(TIMER_FRC2.COUNT + ticks, timer);
+    vPortExitCritical();
+}
+
+void sdk_ets_timer_arm(ets_timer_t *timer, uint32_t milliseconds,
+        bool repeat_flag)
+{
+    sdk_ets_timer_arm_ms_us(timer, milliseconds, repeat_flag,
+            /*value in ms=*/true);
+}
+
+void sdk_ets_timer_arm_us(ets_timer_t *timer, uint32_t useconds,
+        bool repeat_flag)
+{
+    sdk_ets_timer_arm_ms_us(timer, useconds, repeat_flag,
+            /*value in ms=*/false);
+}
+
+/**
+ * Function removes a timer from the pending timers list.
+ */
+void sdk_ets_timer_disarm(ets_timer_t *timer)
+{
+    vPortEnterCritical();
+    ets_timer_t *curr = timer_list;
+    ets_timer_t *prev = 0;
+    while (curr) {
+        if (curr == timer) {
+            if (prev) {
+                prev->next = curr->next;
+            } else {
+                timer_list = curr->next;
+            }
+            break;
+        }
+        prev = curr;
+        curr = curr->next;
+    }
+    vPortExitCritical();
+    timer->next = ETS_TIMER_NOT_ARMED;
+    timer->period_ticks = 0;
+}
+
+/**
+ * Check the list of pending timers for expired ones and process them.
+ */
+static inline void process_pending_timers()
+{
+    vPortEnterCritical();
+    int32_t ticks = TIMER_FRC2.COUNT;
+    while (timer_list) {
+        if (((int32_t)timer_list->fire_ticks - ticks) < 1) {
+            ets_timer_t *timer = timer_list;
+            timer_list = timer->next;
+            timer->next = ETS_TIMER_NOT_ARMED;
+
+            vPortExitCritical();
+            timer->callback(timer->timer_arg);
+            vPortEnterCritical();
+
+            if (timer->next == ETS_TIMER_NOT_ARMED) {
+                if (timer->period_ticks) {
+                    timer->fire_ticks = timer->fire_ticks + timer->period_ticks;
+                    add_pending_timer(timer->fire_ticks, timer);
+                }
+            }
+            ticks = TIMER_FRC2.COUNT;
+        } else {
+            if (timer_list) {
+                set_alarm(timer_list->fire_ticks);
+            }
+            break;
+        }
+    }
+    vPortExitCritical();
+}
+
+/**
+ * .Lfunc002
+ */
+static void IRAM frc2_isr(void *arg)
+{
+    BaseType_t task_woken = 0;
+
+    BaseType_t result = xTaskNotifyFromISR(task_handle, 0, eNoAction, &task_woken);
+    if (result != pdTRUE) {
+        printf("TIMQ_FL:%d!!", (uint32_t)result);
+    }
+
+    portEND_SWITCHING_ISR(task_woken);
+}
+
+/**
+ * .Lfunc007
+ *
+ * Timer task
+ */
+static void timer_task(void* param)
+{
+    while (true) {
+        if (xTaskNotifyWait(0, 0, NULL, portMAX_DELAY) == pdTRUE) {
+            process_pending_timers();
+        }
+    }
+}
+
+void sdk_ets_timer_init()
+{
+    timer_list = 0;
+
+    _xt_isr_attach(INUM_TIMER_FRC2, frc2_isr, NULL);
+
+    /* Original code calls xTaskGenericCreate:
+     * xTaskGenericCreate(task_handle, "rtc_timer_task", 200, 0, 12, &handle,
+     *     NULL, NULL);
+     */
+    xTaskCreate(timer_task, "rtc_timer_task", 200, 0, 12, &task_handle);
+    printf("frc2_timer_task_hdl:%p, prio:%d, stack:%d\n", task_handle, 12, 200);
+
+    TIMER_FRC2.ALARM = 0;
+    TIMER_FRC2.CTRL =  VAL2FIELD(TIMER_CTRL_CLKDIV, TIMER_CLKDIV_16)
+        | TIMER_CTRL_RUN;
+    TIMER_FRC2.LOAD = 0;
+
+    DPORT.INT_ENABLE |= DPORT_INT_ENABLE_TIMER1;
+
+   _xt_isr_unmask(BIT(INUM_TIMER_FRC2));
+}
+
+#endif /* OPEN_LIBMAIN_ETS_TIMER */