linux-kernel - [PATCH v1] usb: typec: altmodes/displayport: Signal hpd low when exiting mode

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Message-ID: <20231009210057.3773877-2-rdbabiera@google.com>
Date:   Mon,  9 Oct 2023 21:00:58 +0000
From:   RD Babiera <rdbabiera@...gle.com>
To:     heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org
Cc:     badhri@...gle.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, RD Babiera <rdbabiera@...gle.com>,
        stable@...r.kernel.org
Subject: [PATCH v1] usb: typec: altmodes/displayport: Signal hpd low when
 exiting mode

Upon receiving an ACK for a sent EXIT_MODE message, the DisplayPort
driver currently resets the status and configuration of the port partner.
The hpd signal is not updated despite being part of the status, so the
Display stack can still transmit video despite typec_altmode_exit placing
the lanes in a Safe State.

Set hpd to low when a sent EXIT_MODE message is ACK'ed.

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: stable@...r.kernel.org
Signed-off-by: RD Babiera <rdbabiera@...gle.com>
---
 drivers/usb/typec/altmodes/displayport.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index f503cb4cd721..718da02036d8 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -307,6 +307,11 @@ static int dp_altmode_vdm(struct typec_altmode *alt,
 			typec_altmode_update_active(alt, false);
 			dp->data.status = 0;
 			dp->data.conf = 0;
+			if (dp->hpd) {
+				drm_connector_oob_hotplug_event(dp->connector_fwnode);
+				dp->hpd = false;
+				sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
+			}
 			break;
 		case DP_CMD_STATUS_UPDATE:
 			dp->data.status = *vdo;

base-commit: 1053c4a4b8fcbd28386e80347e7c82d4d617e352
-- 
2.42.0.609.gbb76f46606-goog