ALT-DP: Don't send DP_ATTENTION until after DP_CONFIG

This CL adds a new variable to the hpd state that enables the pd
policy layer to inform the hpd->DP_ATTENTION converter that at least
one DP_CONFIG message has been received. This control is used to make
sure that DP_ATTENTION messages aren't sent prior the DFP_D being
configured for DP port mode. Some port partners may get confused if
DP_ATTENTION is sent prior to either DP_CONFIG or DP_STATUS.

BRANCH=quiche
BUG=b:192051705
TEST=verifed on kasumi (grunt) that the display is extended correctly
following usbc hotplug events. Previously, this case was failing 1 out
of 3-4 times.

Signed-off-by: Scott Collyer <scollyer@google.com>
Change-Id: I80d576de7fc0075be2b1a838d1ed764ae7828e8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3035785
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Diana Z <dzigterman@chromium.org>
Reviewed-by: Abe Levkoy <alevkoy@chromium.org>
Commit-Queue: Scott Collyer <scollyer@chromium.org>

1 files changed, 35 insertions, 4 deletions

diff --git a/common/usbc/usb_pd_dp_ufp.c b/common/usbc/usb_pd_dp_ufp.c
index d2307a6025..31a3069bb9 100644
--- a/common/usbc/usb_pd_dp_ufp.c
+++ b/common/usbc/usb_pd_dp_ufp.c
@@ -50,6 +50,7 @@ struct hpd_edge {
 struct hpd_info {
 	enum hpd_state state;
 	int count;
+	int send_enable;
 	uint64_t timer;
 	uint64_t last_send_ts;
 	enum hpd_event queue[HPD_QUEUE_DEPTH];
@@ -71,6 +72,17 @@ int pd_ufp_get_dp_opos(int port)
 	return alt_dp_mode_opos[port];
 }
 
+void pd_ufp_enable_hpd_send(int port)
+{
+	/*
+	 * This control is used ensure that a DP_ATTENTION message is not sent
+	 * to the DFP-D before a DP_CONFIG messaage has been received. This
+	 * control is not strictly required by the spec, but some port partners
+	 * will get confused if DP_ATTENTION is sent prior to DP_CONFIG.
+	 */
+	hpd.send_enable = 1;
+}
+
 static void hpd_to_dp_attention(void)
 {
 	int port = hpd_config.port;
@@ -314,19 +326,37 @@ static void manage_hpd(void)
 	 * queued, then send DP_ATTENTION message.
 	 */
 	if (hpd.count > 0) {
-		if ((get_time().val - hpd.last_send_ts) > HPD_T_MIN_DP_ATTEN) {
+		/*
+		 * If at least one hpd event is pending in the queue, send
+		 * a DP_ATTENTION message if a DP_CONFIG message has been
+		 * received and have passed the minimum spacing interval.
+		 */
+		if (hpd.send_enable &&
+		    ((get_time().val - hpd.last_send_ts) >
+		     HPD_T_MIN_DP_ATTEN)) {
 			/* Generate DP_ATTENTION event pending in queue */
 			hpd_to_dp_attention();
 		} else {
+			uint32_t callback_us;
+
 			/*
 			 * Need to wait until until min spacing requirement of
 			 * DP attention messages. Set callback time to the min
 			 * value required. This callback time could be changed
 			 * based on hpd interrupts.
+			 *
+			 * This wait is also used to prevent a DP_ATTENTION
+			 * message from being sent before at least one DP_CONFIG
+			 * message has been received. If DP_ATTENTION messages
+			 * need to be delayed for this reason, then just wait
+			 * the minimum time spacing.
 			 */
-			hook_call_deferred(&manage_hpd_data,
-					   HPD_T_MIN_DP_ATTEN -
-					   (get_time().val - hpd.last_send_ts));
+			callback_us = HPD_T_MIN_DP_ATTEN -
+				(get_time().val - hpd.last_send_ts);
+			if (callback_us <= 0 ||
+			    callback_us > HPD_T_MIN_DP_ATTEN)
+				callback_us = HPD_T_MIN_DP_ATTEN;
+			hook_call_deferred(&manage_hpd_data, callback_us);
 		}
 	}
 
@@ -374,6 +404,7 @@ void usb_pd_hpd_converter_enable(int enable)
 		hpd.count = 0;
 		hpd.timer = 0;
 	        hpd.last_send_ts = 0;
+		hpd.send_enable = 0;
 
 		/* Reset hpd signal edges queue */
 		hpd.edges.head = 0;