linux-kernel - [PATCH 1/1] usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode

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Message-Id: <20250209071926.69625-1-joswang1221@gmail.com>
Date: Sun,  9 Feb 2025 15:19:26 +0800
From: joswang <joswang1221@...il.com>
To: heikki.krogerus@...ux.intel.com
Cc: gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jos Wang <joswang@...ovo.com>
Subject: [PATCH 1/1] usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode

From: Jos Wang <joswang@...ovo.com>

Although some Type-C DRD devices that do not support the DP Sink
function (such as Huawei Mate 40Pro), the Source Port initiates
Enter Mode CMD, but the device responds to Enter Mode ACK, the
Source port then initiates DP Status Update CMD, and the device
responds to DP Status Update NAK.

As PD2.0 spec ("6.4.4.3.4 Enter Mode Command")，A DR_Swap Message
Shall Not be sent during Modal Operation between the Port Partners.
At this time, the source port initiates DR_Swap message through the
"echo device > /sys/class/typec/port0/data_role" command to switch
the data role from host to device. The device will initiate a Hard
Reset for recovery, resulting in the failure of data role swap.

Therefore, when DP Status Update NAK is received, Exit Mode CMD is
initiated to exit the currently entered DP altmode.

Signed-off-by: Jos Wang <joswang@...ovo.com>
---
 drivers/usb/typec/altmodes/displayport.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index ac84a6d64c2f..b09b58d7311d 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -393,6 +393,10 @@ static int dp_altmode_vdm(struct typec_altmode *alt,
 		break;
 	case CMDT_RSP_NAK:
 		switch (cmd) {
+		case DP_CMD_STATUS_UPDATE:
+			if (typec_altmode_exit(alt))
+				dev_err(&dp->alt->dev, "Exit Mode Failed!\n");
+			break;
 		case DP_CMD_CONFIGURE:
 			dp->data.conf = 0;
 			ret = dp_altmode_configured(dp);
-- 
2.17.1