Commit 0ff0705a authored by Hans de Goede's avatar Hans de Goede Committed by Greg Kroah-Hartman
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usb: typec: ucsi: Fix AB BA lock inversion 



Lockdep reports an AB BA lock inversion between ucsi_init() and
ucsi_handle_connector_change():

AB order:

1. ucsi_init takes ucsi->ppm_lock (it runs with that locked for the
   duration of the function)
2. usci_init eventually end up calling ucsi_register_displayport,
   which takes ucsi_connector->lock

BA order:

1. ucsi_handle_connector_change work is started, takes ucsi_connector->lock
2. ucsi_handle_connector_change calls ucsi_send_command which takes
   ucsi->ppm_lock

The ppm_lock really only needs to be hold during 2 functions:
ucsi_reset_ppm() and ucsi_run_command().

This commit fixes the AB BA lock inversion by making ucsi_init drop the
ucsi->ppm_lock before it starts registering ports; and replacing any
ucsi_run_command() calls after this point with ucsi_send_command()
(which is a wrapper around run_command taking the lock while handling
the command).

Some of the replacing of ucsi_run_command with ucsi_send_command
in the helpers used during port registration also fixes a number of
code paths after registration which call ucsi_run_command() without
holding the ppm_lock:
1. ucsi_altmode_update_active() call in ucsi/displayport.c
2. ucsi_register_altmodes() call from ucsi_handle_connector_change()
   (through ucsi_partner_change())

Cc: stable@vger.kernel.org
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Acked-by: default avatarHeikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200809141904.4317-2-hdegoede@redhat.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7a2f2974

drivers/usb/typec/ucsi/ucsi.c

+9 −9
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ void ucsi_altmode_update_active(struct ucsi_connector *con) 
	int i;



	command = UCSI_GET_CURRENT_CAM | UCSI_CONNECTOR_NUMBER(con->num);

	ret = ucsi_run_command(con->ucsi, command, &cur, sizeof(cur));

	ret = ucsi_send_command(con->ucsi, command, &cur, sizeof(cur));

	if (ret < 0) {

		if (con->ucsi->version > 0x0100) {

			dev_err(con->ucsi->dev,
@@ -354,7 +354,7 @@ ucsi_register_altmodes_nvidia(struct ucsi_connector *con, u8 recipient) 
		command |= UCSI_GET_ALTMODE_RECIPIENT(recipient);

		command |= UCSI_GET_ALTMODE_CONNECTOR_NUMBER(con->num);

		command |= UCSI_GET_ALTMODE_OFFSET(i);

		len = ucsi_run_command(con->ucsi, command, &alt, sizeof(alt));

		len = ucsi_send_command(con->ucsi, command, &alt, sizeof(alt));

		/*

		 * We are collecting all altmodes first and then registering.

		 * Some type-C device will return zero length data beyond last
@@ -431,7 +431,7 @@ static int ucsi_register_altmodes(struct ucsi_connector *con, u8 recipient) 
		command |= UCSI_GET_ALTMODE_RECIPIENT(recipient);

		command |= UCSI_GET_ALTMODE_CONNECTOR_NUMBER(con->num);

		command |= UCSI_GET_ALTMODE_OFFSET(i);

		len = ucsi_run_command(con->ucsi, command, alt, sizeof(alt));

		len = ucsi_send_command(con->ucsi, command, alt, sizeof(alt));

		if (len <= 0)

			return len;
@@ -904,7 +904,7 @@ static int ucsi_register_port(struct ucsi *ucsi, int index) 
	/* Get connector capability */

	command = UCSI_GET_CONNECTOR_CAPABILITY;

	command |= UCSI_CONNECTOR_NUMBER(con->num);

	ret = ucsi_run_command(ucsi, command, &con->cap, sizeof(con->cap));

	ret = ucsi_send_command(ucsi, command, &con->cap, sizeof(con->cap));

	if (ret < 0)

		return ret;
@@ -953,8 +953,7 @@ static int ucsi_register_port(struct ucsi *ucsi, int index) 


	/* Get the status */

	command = UCSI_GET_CONNECTOR_STATUS | UCSI_CONNECTOR_NUMBER(con->num);

	ret = ucsi_run_command(ucsi, command, &con->status,

			       sizeof(con->status));

	ret = ucsi_send_command(ucsi, command, &con->status, sizeof(con->status));

	if (ret < 0) {

		dev_err(ucsi->dev, "con%d: failed to get status\n", con->num);

		return 0;
@@ -1044,6 +1043,8 @@ static int ucsi_init(struct ucsi *ucsi) 
		goto err_reset;

	}



	mutex_unlock(&ucsi->ppm_lock);



	/* Register all connectors */

	for (i = 0; i < ucsi->cap.num_connectors; i++) {

		ret = ucsi_register_port(ucsi, i);
@@ -1054,12 +1055,10 @@ static int ucsi_init(struct ucsi *ucsi) 
	/* Enable all notifications */

	ucsi->ntfy = UCSI_ENABLE_NTFY_ALL;

	command = UCSI_SET_NOTIFICATION_ENABLE | ucsi->ntfy;

	ret = ucsi_run_command(ucsi, command, NULL, 0);

	ret = ucsi_send_command(ucsi, command, NULL, 0);

	if (ret < 0)

		goto err_unregister;



	mutex_unlock(&ucsi->ppm_lock);



	return 0;



err_unregister:
@@ -1071,6 +1070,7 @@ err_unregister: 
		con->port = NULL;

	}



	mutex_lock(&ucsi->ppm_lock);

err_reset:

	ucsi_reset_ppm(ucsi);

err:

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