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From: Andrei Kuchynski <akuchynski@chromium.org>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Dmitry Baryshkov <lumag@kernel.org>,
	Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
	Jameson Thies <jthies@google.com>,
	Benson Leung <bleung@chromium.org>,
	Tzung-Bi Shih <tzungbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Guenter Roeck <groeck@chromium.org>,
	Pooja Katiyar <pooja.katiyar@intel.com>,
	Badhri Jagan Sridharan <badhri@google.com>,
	RD Babiera <rdbabiera@google.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	chrome-platform@lists.linux.dev,
	Andrei Kuchynski <akuchynski@chromium.org>
Subject: [PATCH 06/10] Revert "usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode"
Date: Mon, 16 Jun 2025 13:31:43 +0000	[thread overview]
Message-ID: <20250616133147.1835939-7-akuchynski@chromium.org> (raw)
In-Reply-To: <20250616133147.1835939-1-akuchynski@chromium.org>

This reverts commit b4b38ffb38c91afd4dc387608db26f6fc34ed40b.

The commit introduced a deadlock with the cros_ec_typec driver.
The deadlock occurs due to a recursive lock acquisition of
`cros_typec_altmode_work::mutex`.
The call chain is as follows: 
1. cros_typec_altmode_work() acquires the mutex
2. typec_altmode_vdm() -> dp_altmode_vdm() ->
3. typec_altmode_exit() -> cros_typec_altmode_exit()
4. cros_typec_altmode_exit() attempts to acquire the mutex again

This revert is considered safe as no other known driver sends back
DP_CMD_STATUS_UPDATE command with the NAK flag.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/usb/typec/altmodes/displayport.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index b09b58d7311d..ac84a6d64c2f 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -393,10 +393,6 @@ 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);
-- 
2.50.0.rc1.591.g9c95f17f64-goog


  parent reply	other threads:[~2025-06-16 13:33 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-06-16 13:31 [PATCH 00/10] USB Type-C mode selection Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 01/10] usb: typec: Add alt_mode_override field to port property Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 02/10] platform/chrome: cros_ec_typec: Set alt_mode_override flag Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 03/10] usb: typec: ucsi: " Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 04/10] usb: typec: Expose alternate mode priorities via sysfs Andrei Kuchynski
2025-06-17  9:50   ` Heikki Krogerus
2025-06-17 12:38     ` Andrei Kuchynski
2025-06-17 13:28       ` Greg Kroah-Hartman
2025-06-18  2:47         ` Abhishek Pandit-Subedi
2025-06-18 13:42           ` Heikki Krogerus
2025-06-18 19:00             ` Abhishek Pandit-Subedi
2025-06-16 13:31 ` [PATCH 05/10] usb: typec: Implement automated alternate mode selection Andrei Kuchynski
2025-06-16 13:31 ` Andrei Kuchynski [this message]
2025-06-16 14:15   ` [PATCH 06/10] Revert "usb: typec: displayport: Receive DP Status Update NAK request exit dp altmode" Greg Kroah-Hartman
2025-06-16 19:42     ` Andrei Kuchynski
2025-06-17  8:54   ` Heikki Krogerus
2025-06-17 12:54     ` Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 07/10] usb: typec: Report altmode entry status via callback Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 08/10] usb: typec: ucsi: displayport: Propagate DP altmode entry result Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 09/10] platform/chrome: cros_ec_typec: Propagate " Andrei Kuchynski
2025-06-16 13:31 ` [PATCH 10/10] platform/chrome: cros_ec_typec: Report USB4 mode entry status via callback Andrei Kuchynski
2025-06-16 13:34 ` [PATCH 00/10] USB Type-C mode selection Dmitry Baryshkov

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