improve poweroff sequence

When powering off the modem, we must assert the RESET line only when the 
modem has shut down (otherwise it'll cause a hard reset and won't allow 
the modem to shut down properly).

This commit also polls the STATUS pin during poweroff and quits 
immediately once this pin goes high.

src/gpio.c

@@ -64,11 +64,8 @@ int gpio_sequence_poweron(struct EG25Manager *manager)
 
 int gpio_sequence_shutdown(struct EG25Manager *manager)
 {
-    gpiod_line_set_value(manager->gpio_out[GPIO_OUT_RESET], 1);
     gpiod_line_set_value(manager->gpio_out[GPIO_OUT_DISABLE], 1);
-    gpiod_line_set_value(manager->gpio_out[GPIO_OUT_PWRKEY], 1);
+    gpio_sequence_poweron(manager);
-    sleep(1);
-    gpiod_line_set_value(manager->gpio_out[GPIO_OUT_PWRKEY], 0);
 
     g_message("Executed power-off sequence");
 
@@ -175,6 +172,19 @@ int gpio_init(struct EG25Manager *manager)
     return 0;
 }
 
+gboolean gpio_check_poweroff(struct EG25Manager *manager)
+{
+    if (manager->gpio_in[GPIO_IN_STATUS] &&
+        gpiod_line_get_value(manager->gpio_in[GPIO_IN_STATUS]) == 1) {
+
+        // Asserting RESET line to prevent modem from rebooting
+        gpiod_line_set_value(manager->gpio_out[GPIO_OUT_RESET], 1);
+        return TRUE;
+    }
+
+    return FALSE;
+}
+
 void gpio_destroy(struct EG25Manager *manager)
 {
     int i;

src/gpio.h

@@ -15,3 +15,5 @@ int gpio_sequence_poweron(struct EG25Manager *state);
 int gpio_sequence_shutdown(struct EG25Manager *state);
 int gpio_sequence_suspend(struct EG25Manager *state);
 int gpio_sequence_resume(struct EG25Manager *state);
+
+gboolean gpio_check_poweroff(struct EG25Manager *manager);

src/manager.c

@@ -25,6 +25,16 @@ static gboolean quit_timeout_cb(struct EG25Manager *manager)
     return FALSE;
 }
 
+static gboolean gpio_poll_cb(struct EG25Manager *manager)
+{
+    if (gpio_check_poweroff(manager)) {
+        quit_timeout_cb(manager);
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
 static gboolean quit_app(struct EG25Manager *manager)
 {
     g_message("Request to quit...");
@@ -33,10 +43,7 @@ static gboolean quit_app(struct EG25Manager *manager)
         g_message("Powering down the modem...");
         gpio_sequence_shutdown(manager);
         manager->modem_state = EG25_STATE_FINISHING;
-        /*
+        g_timeout_add(500, G_SOURCE_FUNC(gpio_poll_cb), manager);
-         * TODO: add a polling function to check STATUS and RI pins state
-         * (that way we could reduce the poweroff delay)
-         */
         g_timeout_add_seconds(30, G_SOURCE_FUNC(quit_timeout_cb), manager);
     }