Commit a14a1459 authored by Cristian Marussi's avatar Cristian Marussi Committed by Sudeep Holla
Browse files

firmware: arm_scmi: Simplify spinlocks in virtio transport 

Remove unneeded nested irqsave/irqrestore spinlocks.
Add also a few descriptive comments to explain better the system behaviour
at shutdown time.

Link: https://lore.kernel.org/r/20210916103336.7243-2-cristian.marussi@arm.com


Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: default avatarCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent 1cd73200

drivers/firmware/arm_scmi/virtio.c

+21 −8
Original line number Diff line number Diff line
@@ -110,18 +110,16 @@ static void scmi_finalize_message(struct scmi_vio_channel *vioch, 
	if (vioch->is_rx) {

		scmi_vio_feed_vq_rx(vioch, msg);

	} else {

		unsigned long flags;



		spin_lock_irqsave(&vioch->lock, flags);

		/* Here IRQs are assumed to be already disabled by the caller */

		spin_lock(&vioch->lock);

		list_add(&msg->list, &vioch->free_list);

		spin_unlock_irqrestore(&vioch->lock, flags);

		spin_unlock(&vioch->lock);

	}

}



static void scmi_vio_complete_cb(struct virtqueue *vqueue)

{

	unsigned long ready_flags;

	unsigned long flags;

	unsigned int length;

	struct scmi_vio_channel *vioch;

	struct scmi_vio_msg *msg;
@@ -140,7 +138,8 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) 
			goto unlock_ready_out;

		}



		spin_lock_irqsave(&vioch->lock, flags);

		/* IRQs already disabled here no need to irqsave */

		spin_lock(&vioch->lock);

		if (cb_enabled) {

			virtqueue_disable_cb(vqueue);

			cb_enabled = false;
@@ -151,7 +150,7 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) 
				goto unlock_out;

			cb_enabled = true;

		}

		spin_unlock_irqrestore(&vioch->lock, flags);

		spin_unlock(&vioch->lock);



		if (msg) {

			msg->rx_len = length;
@@ -161,11 +160,18 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) 
			scmi_finalize_message(vioch, msg);

		}



		/*

		 * Release ready_lock and re-enable IRQs between loop iterations

		 * to allow virtio_chan_free() to possibly kick in and set the

		 * flag vioch->ready to false even in between processing of

		 * messages, so as to force outstanding messages to be ignored

		 * when system is shutting down.

		 */

		spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);

	}



unlock_out:

	spin_unlock_irqrestore(&vioch->lock, flags);

	spin_unlock(&vioch->lock);

unlock_ready_out:

	spin_unlock_irqrestore(&vioch->ready_lock, ready_flags);

}
@@ -435,6 +441,13 @@ static int scmi_vio_probe(struct virtio_device *vdev) 


static void scmi_vio_remove(struct virtio_device *vdev)

{

	/*

	 * Once we get here, virtio_chan_free() will have already been called by

	 * the SCMI core for any existing channel and, as a consequence, all the

	 * virtio channels will have been already marked NOT ready, causing any

	 * outstanding message on any vqueue to be ignored by complete_cb: now

	 * we can just stop processing buffers and destroy the vqueues.

	 */

	vdev->config->reset(vdev);

	vdev->config->del_vqs(vdev);

	scmi_vdev = NULL;