mei: allow clients on bus to communicate in remove callback

Introduce new intermediate state to allow the clients on the bus
to communicate with the firmware from the remove handler.
This is to enable to perform a clean shutdown.
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20210206144325.25682-2-tomas.winkler@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/bus.c

@@ -44,7 +44,8 @@ ssize_t __mei_cl_send(struct mei_cl *cl, u8 *buf, size_t length, u8 vtag,
 	bus = cl->dev;
 
 	mutex_lock(&bus->device_lock);
-	if (bus->dev_state != MEI_DEV_ENABLED) {
+	if (bus->dev_state != MEI_DEV_ENABLED &&
+	    bus->dev_state != MEI_DEV_POWERING_DOWN) {
 		rets = -ENODEV;
 		goto out;
 	}
@@ -128,7 +129,8 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length, u8 *vtag,
 	bus = cl->dev;
 
 	mutex_lock(&bus->device_lock);
-	if (bus->dev_state != MEI_DEV_ENABLED) {
+	if (bus->dev_state != MEI_DEV_ENABLED &&
+	    bus->dev_state != MEI_DEV_POWERING_DOWN) {
 		rets = -ENODEV;
 		goto out;
 	}

drivers/misc/mei/client.c

@@ -990,7 +990,8 @@ int mei_cl_disconnect(struct mei_cl *cl)
 		return 0;
 	}
 
-	if (dev->dev_state == MEI_DEV_POWER_DOWN) {
+	if (dev->dev_state == MEI_DEV_POWERING_DOWN ||
+	    dev->dev_state == MEI_DEV_POWER_DOWN) {
 		cl_dbg(dev, cl, "Device is powering down, don't bother with disconnection\n");
 		mei_cl_set_disconnected(cl);
 		return 0;

drivers/misc/mei/init.c

@@ -303,9 +303,12 @@ void mei_stop(struct mei_device *dev)
 	dev_dbg(dev->dev, "stopping the device.\n");
 
 	mutex_lock(&dev->device_lock);
-	mei_set_devstate(dev, MEI_DEV_POWER_DOWN);
+	mei_set_devstate(dev, MEI_DEV_POWERING_DOWN);
 	mutex_unlock(&dev->device_lock);
 	mei_cl_bus_remove_devices(dev);
+	mutex_lock(&dev->device_lock);
+	mei_set_devstate(dev, MEI_DEV_POWER_DOWN);
+	mutex_unlock(&dev->device_lock);
 
 	mei_cancel_work(dev);
 

drivers/misc/mei/mei_dev.h

@@ -57,6 +57,7 @@ enum mei_dev_state {
 	MEI_DEV_ENABLED,
 	MEI_DEV_RESETTING,
 	MEI_DEV_DISABLED,
+	MEI_DEV_POWERING_DOWN,
 	MEI_DEV_POWER_DOWN,
 	MEI_DEV_POWER_UP
 };