esp8266: Add alternative event loop implementation.

This implementation provides the same interface and uses the same
datastructures as used by BootROM, i.e. is a drop-in replacement for it.
But it offers one advantage: it allows to run single iteration of
event-pumping loop.

Original BootROM function are renamed, prefixed with underscore. There's
a switch which allows to use forward calls to them, for compatibility
testing.

The implementation also includes workarounds for hardware timer handler,
and these workarounds may be SDK version specific.

esp8266/eagle.rom.addr.v6.ld

@@ -132,12 +132,12 @@ PROVIDE ( ets_memcmp = 0x400018d4 );
 PROVIDE ( ets_memcpy = 0x400018b4 );
 PROVIDE ( ets_memmove = 0x400018c4 );
 PROVIDE ( ets_memset = 0x400018a4 );
-PROVIDE ( ets_post = 0x40000e24 );
+PROVIDE ( _ets_post = 0x40000e24 );
 PROVIDE ( ets_printf = 0x400024cc );
 PROVIDE ( ets_putc = 0x40002be8 );
 PROVIDE ( ets_rtc_int_register = 0x40002a40 );
-PROVIDE ( ets_run = 0x40000e04 );
-PROVIDE ( ets_set_idle_cb = 0x40000dc0 );
+PROVIDE ( _ets_run = 0x40000e04 );
+PROVIDE ( _ets_set_idle_cb = 0x40000dc0 );
 PROVIDE ( ets_set_user_start = 0x40000fbc );
 PROVIDE ( ets_str2macaddr = 0x40002af8 );
 PROVIDE ( ets_strcmp = 0x40002aa8 );
@@ -146,12 +146,12 @@ PROVIDE ( ets_strlen = 0x40002ac8 );
 PROVIDE ( ets_strncmp = 0x40002ab8 );
 PROVIDE ( ets_strncpy = 0x40002a98 );
 PROVIDE ( ets_strstr = 0x40002ad8 );
-PROVIDE ( ets_task = 0x40000dd0 );
+PROVIDE ( _ets_task = 0x40000dd0 );
 PROVIDE ( ets_timer_arm = 0x40002cc4 );
 PROVIDE ( ets_timer_disarm = 0x40002d40 );
 PROVIDE ( ets_timer_done = 0x40002d80 );
 PROVIDE ( ets_timer_handler_isr = 0x40002da8 );
-PROVIDE ( ets_timer_init = 0x40002e68 );
+PROVIDE ( _ets_timer_init = 0x40002e68 );
 PROVIDE ( ets_timer_setfn = 0x40002c48 );
 PROVIDE ( ets_uart_printf = 0x40002544 );
 PROVIDE ( ets_update_cpu_frequency = 0x40002f04 );

esp8266/ets_alt_task.c

+#include <stdio.h>
+#include "osapi.h"
+#include "os_type.h"
+#include "ets_sys.h"
+#include "etshal.h"
+
+// Use standard ets_task or alternative impl
+#define USE_ETS_TASK 0
+
+#define MP_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
+
+struct task_entry {
+    os_event_t *queue;
+    os_task_t task;
+    uint8_t qlen;
+    uint8_t prio;
+    int8_t i_get;
+    int8_t i_put;
+};
+
+static void (*idle_cb)(void *);
+static void *idle_arg;
+
+#define FIRST_PRIO 0x14
+#define LAST_PRIO 0x20
+#define PRIO2ID(prio) ((prio) - FIRST_PRIO)
+
+volatile struct task_entry emu_tasks[PRIO2ID(LAST_PRIO) + 1];
+
+static inline int prio2id(uint8_t prio) {
+    int id = PRIO2ID(prio);
+    if (id < 0 || id >= MP_ARRAY_SIZE(emu_tasks)) {
+        printf("task prio out of range: %d\n", prio);
+        while (1);
+    }
+    return id;
+}
+
+void dump_task(int prio, volatile struct task_entry *t) {
+    printf("q for task %d: queue: %p, get ptr: %d, put ptr: %d, qlen: %d\n",
+        prio, t->queue, t->i_get, t->i_put, t->qlen);
+}
+
+void dump_tasks(void) {
+    for (int i = 0; i < MP_ARRAY_SIZE(emu_tasks); i++) {
+        if (emu_tasks[i].qlen) {
+            dump_task(i + FIRST_PRIO, &emu_tasks[i]);
+        }
+    }
+    printf("====\n");
+}
+
+bool ets_task(os_task_t task, uint8 prio, os_event_t *queue, uint8 qlen) {
+    static unsigned cnt;
+    printf("#%d ets_task(%p, %d, %p, %d)\n", cnt++, task, prio, queue, qlen);
+#if USE_ETS_TASK
+    return _ets_task(task, prio, queue, qlen);
+#else
+    int id = prio2id(prio);
+    emu_tasks[id].task = task;
+    emu_tasks[id].queue = queue;
+    emu_tasks[id].qlen = qlen;
+    emu_tasks[id].i_get = 0;
+    emu_tasks[id].i_put = 0;
+    return true;
+#endif
+}
+
+bool ets_post(uint8 prio, os_signal_t sig, os_param_t param) {
+//    static unsigned cnt; printf("#%d ets_post(%d, %x, %x)\n", cnt++, prio, sig, param);
+#if USE_ETS_TASK
+    return _ets_post(prio, sig, param);
+#else
+    ets_intr_lock();
+
+    const int id = prio2id(prio);
+    os_event_t *q = emu_tasks[id].queue;
+    if (emu_tasks[id].i_put == -1) {
+        // queue is full
+        printf("ets_post: task %d queue full\n", prio);
+        return false;
+    }
+    q = &q[emu_tasks[id].i_put++];
+    q->sig = sig;
+    q->par = param;
+    if (emu_tasks[id].i_put == emu_tasks[id].qlen) {
+        emu_tasks[id].i_put = 0;
+    }
+    if (emu_tasks[id].i_put == emu_tasks[id].i_get) {
+        // queue got full
+        emu_tasks[id].i_put = -1;
+    }
+    //printf("after ets_post: "); dump_task(prio, &emu_tasks[id]);
+    //dump_tasks();
+
+    ets_intr_unlock();
+
+    return true;
+#endif
+}
+
+bool ets_loop_iter(void) {
+    //static unsigned cnt;
+    bool progress = false;
+    for (volatile struct task_entry *t = emu_tasks; t < &emu_tasks[MP_ARRAY_SIZE(emu_tasks)]; t++) {
+        ets_intr_lock();
+        //printf("etc_loop_iter: "); dump_task(t - emu_tasks + FIRST_PRIO, t);
+        if (t->i_get != t->i_put) {
+            progress = true;
+            //printf("#%d Calling task %d(%p) (%x, %x)\n", cnt++,
+            //    t - emu_tasks + FIRST_PRIO, t->task, t->queue[t->i_get].sig, t->queue[t->i_get].par);
+            //ets_intr_unlock();
+            t->task(&t->queue[t->i_get]);
+            //ets_intr_lock();
+            //printf("Done calling task %d\n", t - emu_tasks + FIRST_PRIO);
+            if (t->i_put == -1) {
+                t->i_put = t->i_get;
+            }
+            if (++t->i_get == t->qlen) {
+                t->i_get = 0;
+            }
+        }
+        ets_intr_unlock();
+    }
+    return progress;
+}
+
+#if SDK_BELOW_1_1_1
+void my_timer_isr(void *arg) {
+//    uart0_write_char('+');
+    ets_post(0x1f, 0, 0);
+}
+
+// Timer init func is in ROM, and calls ets_task by relative addr directly in ROM
+// so, we have to re-init task using our handler
+void ets_timer_init() {
+    printf("ets_timer_init\n");
+//    _ets_timer_init();
+    ets_isr_attach(10, my_timer_isr, NULL);
+    SET_PERI_REG_MASK(0x3FF00004, 4);
+    ETS_INTR_ENABLE(10);
+    ets_task((os_task_t)0x40002E3C, 0x1f, (os_event_t*)0x3FFFDDC0, 4);
+
+    WRITE_PERI_REG(PERIPHS_TIMER_BASEDDR + 0x30, 0);
+    WRITE_PERI_REG(PERIPHS_TIMER_BASEDDR + 0x28, 0x88);
+    WRITE_PERI_REG(PERIPHS_TIMER_BASEDDR + 0x30, 0);
+    printf("Installed timer ISR\n");
+}
+#endif
+
+bool ets_run(void) {
+#if USE_ETS_TASK
+    #if SDK_BELOW_1_1_1
+    ets_isr_attach(10, my_timer_isr, NULL);
+    #endif
+    _ets_run();
+#else
+//    ets_timer_init();
+    *(char*)0x3FFFC6FC = 0;
+    ets_intr_lock();
+    printf("ets_alt_task: ets_run\n");
+    dump_tasks();
+    ets_intr_unlock();
+    while (1) {
+        if (!ets_loop_iter()) {
+            //printf("idle\n");
+            ets_intr_lock();
+            if (idle_cb) {
+                idle_cb(idle_arg);
+            }
+            asm("waiti 0");
+            ets_intr_unlock();
+        }
+    }
+#endif
+}
+
+void ets_set_idle_cb(void (*handler)(void *), void *arg) {
+    //printf("ets_set_idle_cb(%p, %p)\n", handler, arg);
+    idle_cb = handler;
+    idle_arg = arg;
+}

esp8266/ets_alt_task.h

+bool ets_loop_iter(void);