cr50:ap_state: reenable detect ap on interrupt

ap_state doesn't disable/enable the detect ap interrupt correctly. This
means cr50 is mostly just polling the AP state. Cr50 may not realize the
AP is up until almost a second after it first turned on. This change
reenables the detect ap on interrupt while debouncing the AP state or if
Cr50 thinks the AP is off, so cr50 can more quickly detect the
transition from off to on.

This issue doesn't affect devices that detect the AP with TPM_RST_L,
because we never disable the TPM_RST_L interrupt and that handler calls
ap_on_deferred directly.

BUG=b:71866206
BRANCH=cr50
TEST=run power_state:rec on Dru and make sure there are no tpm irq
timeouts.

Change-Id: I67388f9dce94fb22efe5755a0de563e5af42f8f5
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/869410
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/board/cr50/ap_state.c b/board/cr50/ap_state.c
index e9ddea5640..5bf764ec7c 100644
--- a/board/cr50/ap_state.c
+++ b/board/cr50/ap_state.c
@@ -181,6 +181,14 @@ static void ap_detect(void)
 		}
 
 		return;
+	} else if (!board_detect_ap_with_tpm_rst()) {
+		/*
+		 * If the signal is low, cr50 will enter the debouncing state or
+		 * off. Either way, cr50 is waiting for the signal to go high.
+		 * Reenable the interrupt, so cr50 can immediately detect it
+		 * instead of relying on the 1s polling.
+		 */
+		gpio_enable_interrupt(GPIO_DETECT_AP);
 	}
 
 	/* AP wasn't detected.  If we're already off, done. */
@@ -204,9 +212,5 @@ static void ap_detect(void)
 		set_state(DEVICE_STATE_INIT_DEBOUNCING);
 	else
 		set_state(DEVICE_STATE_DEBOUNCING);
-
-	/* If we're using AP UART RX for detect, enable its interrupt */
-	if (!board_detect_ap_with_tpm_rst())
-		gpio_enable_interrupt(GPIO_DETECT_AP);
 }
 DECLARE_HOOK(HOOK_SECOND, ap_detect, HOOK_PRIO_DEFAULT);