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usb: typec: ucsi: displayport: Fix deadlock
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commit 364618c upstream.

This patch introduces the ucsi_con_mutex_lock / ucsi_con_mutex_unlock
functions to the UCSI driver. ucsi_con_mutex_lock ensures the connector
mutex is only locked if a connection is established and the partner pointer
is valid. This resolves a deadlock scenario where
ucsi_displayport_remove_partner holds con->mutex waiting for
dp_altmode_work to complete while dp_altmode_work attempts to acquire it.

Cc: stable <stable@kernel.org>
Fixes: af8622f ("usb: typec: ucsi: Support for DisplayPort alt mode")
Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250424084429.3220757-2-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Andrei Kuchynski authored and Greg Kroah-Hartman committed May 22, 2025
1 parent d8ef614 commit f32451c
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Showing 3 changed files with 48 additions and 8 deletions.
19 changes: 11 additions & 8 deletions drivers/usb/typec/ucsi/displayport.c
Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,8 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
u8 cur = 0;
int ret;

mutex_lock(&dp->con->lock);
if (!ucsi_con_mutex_lock(dp->con))
return -ENOTCONN;

if (!dp->override && dp->initialized) {
const struct typec_altmode *p = typec_altmode_get_partner(alt);
Expand Down Expand Up @@ -100,7 +101,7 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
schedule_work(&dp->work);
ret = 0;
err_unlock:
mutex_unlock(&dp->con->lock);
ucsi_con_mutex_unlock(dp->con);

return ret;
}
Expand All @@ -112,7 +113,8 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
u64 command;
int ret = 0;

mutex_lock(&dp->con->lock);
if (!ucsi_con_mutex_lock(dp->con))
return -ENOTCONN;

if (!dp->override) {
const struct typec_altmode *p = typec_altmode_get_partner(alt);
Expand Down Expand Up @@ -144,7 +146,7 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
schedule_work(&dp->work);

out_unlock:
mutex_unlock(&dp->con->lock);
ucsi_con_mutex_unlock(dp->con);

return ret;
}
Expand Down Expand Up @@ -202,20 +204,21 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
int cmd = PD_VDO_CMD(header);
int svdm_version;

mutex_lock(&dp->con->lock);
if (!ucsi_con_mutex_lock(dp->con))
return -ENOTCONN;

if (!dp->override && dp->initialized) {
const struct typec_altmode *p = typec_altmode_get_partner(alt);

dev_warn(&p->dev,
"firmware doesn't support alternate mode overriding\n");
mutex_unlock(&dp->con->lock);
ucsi_con_mutex_unlock(dp->con);
return -EOPNOTSUPP;
}

svdm_version = typec_altmode_get_svdm_version(alt);
if (svdm_version < 0) {
mutex_unlock(&dp->con->lock);
ucsi_con_mutex_unlock(dp->con);
return svdm_version;
}

Expand Down Expand Up @@ -259,7 +262,7 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
break;
}

mutex_unlock(&dp->con->lock);
ucsi_con_mutex_unlock(dp->con);

return 0;
}
Expand Down
34 changes: 34 additions & 0 deletions drivers/usb/typec/ucsi/ucsi.c
Original file line number Diff line number Diff line change
Expand Up @@ -1398,6 +1398,40 @@ void ucsi_set_drvdata(struct ucsi *ucsi, void *data)
}
EXPORT_SYMBOL_GPL(ucsi_set_drvdata);

/**
* ucsi_con_mutex_lock - Acquire the connector mutex
* @con: The connector interface to lock
*
* Returns true on success, false if the connector is disconnected
*/
bool ucsi_con_mutex_lock(struct ucsi_connector *con)
{
bool mutex_locked = false;
bool connected = true;

while (connected && !mutex_locked) {
mutex_locked = mutex_trylock(&con->lock) != 0;
connected = con->status.flags & UCSI_CONSTAT_CONNECTED;
if (connected && !mutex_locked)
msleep(20);
}

connected = connected && con->partner;
if (!connected && mutex_locked)
mutex_unlock(&con->lock);

return connected;
}

/**
* ucsi_con_mutex_unlock - Release the connector mutex
* @con: The connector interface to unlock
*/
void ucsi_con_mutex_unlock(struct ucsi_connector *con)
{
mutex_unlock(&con->lock);
}

/**
* ucsi_create - Allocate UCSI instance
* @dev: Device interface to the PPM (Platform Policy Manager)
Expand Down
3 changes: 3 additions & 0 deletions drivers/usb/typec/ucsi/ucsi.h
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@

struct ucsi;
struct ucsi_altmode;
struct ucsi_connector;

/* UCSI offsets (Bytes) */
#define UCSI_VERSION 0
Expand Down Expand Up @@ -62,6 +63,8 @@ int ucsi_register(struct ucsi *ucsi);
void ucsi_unregister(struct ucsi *ucsi);
void *ucsi_get_drvdata(struct ucsi *ucsi);
void ucsi_set_drvdata(struct ucsi *ucsi, void *data);
bool ucsi_con_mutex_lock(struct ucsi_connector *con);
void ucsi_con_mutex_unlock(struct ucsi_connector *con);

void ucsi_connector_change(struct ucsi *ucsi, u8 num);

Expand Down

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