ish: add more explanations comments for reset flow in aontask
BRANCH=none
TEST=ISH still reset properly on arcada
@@ -558,8 +558,33 @@ static void handle_reset(int pm_state)
sram_power(0);
while (1) {
-
- /* check if host ish driver already set the DMA enable flag */
+ /**
+ * check if host ish driver already set the DMA enable flag
+ *
+ * ISH FW and ISH ipc host driver using IPC_ISH_RMP2 register
+ * for synchronization during ISH boot.
+ * ISH ipc host driver will set DMA_ENABLED_MASK bit when it
+ * is loaded and starts, and clear this bit when it is removed.
+ *
+ * see: https://github.com/torvalds/linux/blob/master/drivers/
+ * hid/intel-ish-hid/ipc/ipc.c
+ *
+ * we have two kinds of reset situations need to handle here:
+ * 1: reset ISH via uart console cmd or ectool host cmd
+ * 2: S0 -> Sx (reset_prep interrupt)
+ *
+ * for #1, ISH ipc host driver no changed states,
+ * DMA_ENABLED_MASK bit always set, so, will reset ISH directly
+ *
+ * for #2, ISH ipc host driver changed states, and cleared
+ * DMA_ENABLED_MASK bit, then ISH FW received reset_prep
+ * interrupt, ISH will stay in this while loop (most time in
+ * halt state), waiting for DMA_ENABLED_MASK bit was set and
+ * reset ISH then. Since ISH ROM have no power managment, stay
+ * in aontask can save more power especially if system stay in
+ * Sx for long time.
+ *
+ */
if (IPC_ISH_RMP2 & DMA_ENABLED_MASK) {
/* clear ISH2HOST doorbell register */
@@ -570,12 +595,13 @@ static void handle_reset(int pm_state)
/* reset ISH minute-ia cpu core, will goto ISH ROM */
ish_mia_reset();
+
+ __builtin_unreachable();
}
ish_mia_halt();
}
- __builtin_unreachable();
}
static void handle_unknown_state(void)
