Merge tag 'scmi-fixes-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep...

[sfrench/cifs-2.6.git] / drivers / firmware / arm_scmi / virtio.c

diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c
index 224577f869286c75ae2a277b738c2613b79ecfa1..11e8efb7137512fb292bb6055501829bec0cc881 100644 (file)
--- a/drivers/firmware/arm_scmi/virtio.c
+++ b/drivers/firmware/arm_scmi/virtio.c
@@ -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);
 }
@@ -384,8 +390,11 @@ static int scmi_vio_probe(struct virtio_device *vdev)
        struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
 
        /* Only one SCMI VirtiO device allowed */
-       if (scmi_vdev)
-               return -EINVAL;
+       if (scmi_vdev) {
+               dev_err(dev,
+                       "One SCMI Virtio device was already initialized: only one allowed.\n");
+               return -EBUSY;
+       }
 
        have_vq_rx = scmi_vio_have_vq_rx(vdev);
        vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
@@ -428,16 +437,25 @@ static int scmi_vio_probe(struct virtio_device *vdev)
        }
 
        vdev->priv = channels;
-       scmi_vdev = vdev;
+       /* Ensure initialized scmi_vdev is visible */
+       smp_store_mb(scmi_vdev, vdev);
 
        return 0;
 }
 
 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;
+       /* Ensure scmi_vdev is visible as NULL */
+       smp_store_mb(scmi_vdev, NULL);
 }
 
 static int scmi_vio_validate(struct virtio_device *vdev)
@@ -476,7 +494,7 @@ static int __init virtio_scmi_init(void)
        return register_virtio_driver(&virtio_scmi_driver);
 }
 
-static void __exit virtio_scmi_exit(void)
+static void virtio_scmi_exit(void)
 {
        unregister_virtio_driver(&virtio_scmi_driver);
 }