poppy: If base ADC value is unclear, try reading it again

If the base ADC value does not clearly indicate attach, reverse
attach, or disconnect, read the ADC value again in 500ms.

This time should be long enough that even if the ADC value is
wrong, it would not use an inconsiderate amount of power.

BRANCH=none
BUG=b:67970530
TEST=Connect 6K and 30K resistors in parallel between DET and GND
     pin, EC detects an unclear 27 mV ADC value, and retries
     every 500ms until the 6K resistor is removed and a clear
     attach value is read (154 mV).
TEST=Connect base in reverse, ADC value is around 475 mV, and
     ADC is not polled again.
TEST=Disconnect base, ADC value is at maximum (2816 mV), and ADC
     is not polled again.

Change-Id: I616114afc683608b853c18d0a081c6cd1e150c75
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/727790
Reviewed-by: Furquan Shaikh <furquan@chromium.org>

1 files changed, 17 insertions, 10 deletions

diff --git a/board/poppy/board.c b/board/poppy/board.c
index 424e77b1b4..c3b45aaa2f 100644
--- a/board/poppy/board.c
+++ b/board/poppy/board.c
@@ -139,12 +139,14 @@ void anx74xx_cable_det_interrupt(enum gpio_signal signal)
 }
 #endif
 
+/* Base detection and debouncing */
+#define BASE_DETECT_DEBOUNCE_US (20 * MSEC)
+
 /*
- * Base detection and debouncing
- *
- * TODO(b/35585396): Fine-tune these values.
+ * If the base status is unclear (i.e. not within expected ranges, read
+ * the ADC value again every 500ms.
  */
-#define BASE_DETECT_DEBOUNCE_US (20 * MSEC)
+#define BASE_DETECT_RETRY_US (500 * MSEC)
 
 /*
  * rev0: Lid has 100K pull-up, base has 5.1K pull-down, so the ADC
@@ -167,6 +169,9 @@ void anx74xx_cable_det_interrupt(enum gpio_signal signal)
 #define BASE_DETECT_REVERSE_MIN_MV 450
 #define BASE_DETECT_REVERSE_MAX_MV 500
 
+/* Minimum ADC value to indicate base is disconnected for sure */
+#define BASE_DETECT_DISCONNECT_MIN_MV 1500
+
 /*
  * Base EC pulses detection pin for 500 us to signal out of band USB wake (that
  * can be used to wake system from deep S3).
@@ -259,13 +264,15 @@ static void base_detect_deferred(void)
 			CPRINTS("Sending event to AP");
 			host_set_single_event(EC_HOST_EVENT_KEY_PRESSED);
 		}
-	} else {
-		/*
-		 * TODO(b/35585396): Figure out what to do with
-		 * other ADC values that do not clearly indicate base
-		 * presence or absence.
-		 */
+	} else if ((v >= BASE_DETECT_REVERSE_MIN_MV &&
+		    v <= BASE_DETECT_REVERSE_MAX_MV) ||
+		   v >= BASE_DETECT_DISCONNECT_MIN_MV) {
+		/* TODO(b/35585396): Handle reverse connection separately. */
 		base_detect_change(BASE_DISCONNECTED);
+	} else {
+		/* Unclear base status, schedule again in a while. */
+		hook_call_deferred(&base_detect_deferred_data,
+				   BASE_DETECT_RETRY_US);
 	}
 }