platform/chrome: cros_ec_proto: Lock device when updating MKBP version

The cros_ec_get_host_command_version_mask() function requires that the
caller must have ec_dev->lock mutex before calling it. This requirement
was not met and as a result it was possible that two commands were sent
to the device at the same time.

The problem was observed while using UART backend which doesn't use any
additional locks, unlike SPI backend which locks the controller until
response is received.

Fixes: f74c755 ("platform/chrome: cros_ec_proto: Update version on GET_NEXT_EVENT failure")
Cc: stable@vger.kernel.org
Signed-off-by: Patryk Duda <patrykd@google.com>
Link: https://lore.kernel.org/r/20240730104425.607083-1-patrykd@google.com
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

drivers/platform/chrome/cros_ec_proto.c

@@ -813,9 +813,11 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev,
 	if (ret == -ENOPROTOOPT) {
 		dev_dbg(ec_dev->dev,
 			"GET_NEXT_EVENT returned invalid version error.\n");
+		mutex_lock(&ec_dev->lock);
 		ret = cros_ec_get_host_command_version_mask(ec_dev,
 							EC_CMD_GET_NEXT_EVENT,
 							&ver_mask);
+		mutex_unlock(&ec_dev->lock);
 		if (ret < 0 || ver_mask == 0)
 			/*
 			 * Do not change the MKBP supported version if we can't