synaptics_s3708: Poll interrupt after arming LPWG

Poll the interrupt line that the touch controller uses to report a
pending event when we arm the low-power wake gesture (double-tap
detector). If it's active (low), post an event to read the status
register, which will reset the interrupt line and allow us to detect a
subsequent double-touch gesture via the ISR.

This fixes an issue where sometimes double-touch would fail to function
until the screen is toggled on and off. The cause was a pending touch
event leading to the interrupt line being held low prior to when the
sensor hub registered the ISR.

Bug: 32971126
Test: drag finger across screen and turn the screen off with the power
button to increase the likelihood of a pending touch event when
double-touch is enabled, then use logcat to verify that the failure
condition was triggered and solved by this change (reproducibility under
these conditions seems to be ~25%).

Change-Id: I375ff57e8240b392bbce2de96ceb99556d95e6fa

1 files changed, 12 insertions, 1 deletions

diff --git a/firmware/src/drivers/synaptics_s3708/synaptics_s3708.c b/firmware/src/drivers/synaptics_s3708/synaptics_s3708.c
index 1706a660..af7c5259 100644
--- a/firmware/src/drivers/synaptics_s3708/synaptics_s3708.c
+++ b/firmware/src/drivers/synaptics_s3708/synaptics_s3708.c
@@ -104,6 +104,7 @@ enum TaskState
 {
     STATE_ENABLE_0,
     STATE_ENABLE_1,
+    STATE_ENABLE_2,
     STATE_DISABLE_0,
     STATE_INT_HANDLE_0,
     STATE_INT_HANDLE_1,
@@ -438,7 +439,17 @@ static void processI2cResponse(struct I2cTransfer *xfer)
             if (mTask.retryCnt < HACK_RETRY_SKIP_COUNT) {
                 setRetryTimer();
             } else {
-                setReportingMode(S3708_REPORT_MODE_LPWG, STATE_IDLE);
+                setReportingMode(S3708_REPORT_MODE_LPWG, STATE_ENABLE_2);
+            }
+            break;
+
+        case STATE_ENABLE_2:
+            // Poll the GPIO line to see if it is low/active (it might have been
+            // low when we enabled the ISR, e.g. due to a pending touch event).
+            // Only do this after arming the LPWG, so it happens after we know
+            // that we can talk to the touch controller.
+            if (!gpioGet(mTask.pin)) {
+                osEnqueuePrivateEvt(EVT_SENSOR_TOUCH_INTERRUPT, NULL, NULL, mTask.id);
             }
             break;