linux-kernel - [PATCH v4 8/8] usb: typec: ucsi: Enforce mode selection for cros_ec

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Message-ID: <20260113130536.3068311-9-akuchynski@chromium.org>
Date: Tue, 13 Jan 2026 13:05:36 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chrome-platform@...ts.linux.dev
Cc: Tzung-Bi Shih <tzungbi@...nel.org>,
	Guenter Roeck <groeck@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Łukasz Bartosik <ukaszb@...omium.org>,
	Abel Vesa <abel.vesa@...aro.org>,
	Pooja Katiyar <pooja.katiyar@...el.com>,
	Johan Hovold <johan@...nel.org>,
	Hsin-Te Yuan <yuanhsinte@...omium.org>,
	Madhu M <madhu.m@...el.com>,
	Venkat Jayaraman <venkat.jayaraman@...el.com>,
	Andrei Kuchynski <akuchynski@...omium.org>
Subject: [PATCH v4 8/8] usb: typec: ucsi: Enforce mode selection for cros_ec_ucsi

The mode selection sequence is initiated by the driver after all partner
alternate modes have been successfully registered.
When a partner is disconnected, the driver also stops the mode selection
process and releases resources via `typec_mode_selection_delete`.

Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>
---
 drivers/usb/typec/ucsi/cros_ec_ucsi.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/usb/typec/ucsi/cros_ec_ucsi.c b/drivers/usb/typec/ucsi/cros_ec_ucsi.c
index eed2a7d0ebc63..437a2982a9d51 100644
--- a/drivers/usb/typec/ucsi/cros_ec_ucsi.c
+++ b/drivers/usb/typec/ucsi/cros_ec_ucsi.c
@@ -16,6 +16,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/wait.h>
+#include <linux/usb/typec_altmode.h>
 
 #include "ucsi.h"
 
@@ -33,6 +34,11 @@
 /* Number of times to attempt recovery from a write timeout before giving up. */
 #define WRITE_TMO_CTR_MAX	5
 
+/* Delay between mode entry/exit attempts, ms */
+static const unsigned int mode_selection_delay = 1000;
+/* Timeout for a mode entry attempt, ms */
+static const unsigned int mode_selection_timeout = 4000;
+
 struct cros_ucsi_data {
 	struct device *dev;
 	struct ucsi *ucsi;
@@ -134,6 +140,19 @@ static int cros_ucsi_sync_control(struct ucsi *ucsi, u64 cmd, u32 *cci,
 	return ret;
 }
 
+static void cros_ucsi_add_partner_altmodes(struct ucsi_connector *con)
+{
+	if (con->ucsi->cap.features & UCSI_CAP_ALT_MODE_OVERRIDE)
+		typec_mode_selection_start(con->partner,
+				mode_selection_delay, mode_selection_timeout);
+}
+
+static void cros_ucsi_remove_partner_altmodes(struct ucsi_connector *con)
+{
+	if (con->ucsi->cap.features & UCSI_CAP_ALT_MODE_OVERRIDE)
+		typec_mode_selection_delete(con->partner);
+}
+
 static const struct ucsi_operations cros_ucsi_ops = {
 	.read_version = cros_ucsi_read_version,
 	.read_cci = cros_ucsi_read_cci,
@@ -141,6 +160,8 @@ static const struct ucsi_operations cros_ucsi_ops = {
 	.read_message_in = cros_ucsi_read_message_in,
 	.async_control = cros_ucsi_async_control,
 	.sync_control = cros_ucsi_sync_control,
+	.add_partner_altmodes = cros_ucsi_add_partner_altmodes,
+	.remove_partner_altmodes = cros_ucsi_remove_partner_altmodes,
 };
 
 static void cros_ucsi_work(struct work_struct *work)
-- 
2.52.0.457.g6b5491de43-goog