6.12-stable review patch. If anyone has any objections, please let me know.
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From: Junnan Wu junnan01.wu@samsung.com
[ Upstream commit e8faa8a466f61f4ae07069ed6b0872f602f1cba9 ]
After commit 20bda12a0ea0 (“firmware: arm_scmi: Make VirtIO transport a standalone driver”), the VirtIO transport probes independently. During scmi_virtio_probe, scmi_probe() is called, which intune invokes scmi_protocol_acquire() that sends a message over the virtqueue and waits for a reply.
Previously, DRIVER_OK was only set after scmi_vio_probe, in the core virtio via virtio_dev_probe(). According to the Virtio spec (3.1 Device Initialization): | The driver MUST NOT send any buffer available notifications to the | device before setting DRIVER_OK.
Some type-1 hypervisors block available-buffer notifications until the driver is marked OK. In such cases, scmi_vio_probe stalls in scmi_wait_for_reply(), and the probe never completes.
Resolve this by setting DRIVER_OK immediately after the device-specific setup, so scmi_probe() can safely send notifications.
Note after splitting the transports into modules, the probe sequence changed a bit. We can no longer rely on virtio_device_ready() being called by the core in virtio_dev_probe(), because scmi_vio_probe() doesn’t complete until the core SCMI stack runs scmi_probe(), which immediately issues the initial BASE protocol exchanges.
Fixes: 20bda12a0ea0 ("firmware: arm_scmi: Make VirtIO transport a standalone driver") Signed-off-by: Junnan Wu junnan01.wu@samsung.com Message-Id: 20250812075343.3201365-1-junnan01.wu@samsung.com Signed-off-by: Sudeep Holla sudeep.holla@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/arm_scmi/transports/virtio.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/firmware/arm_scmi/transports/virtio.c b/drivers/firmware/arm_scmi/transports/virtio.c index d349766bc0b26..f78b87f334037 100644 --- a/drivers/firmware/arm_scmi/transports/virtio.c +++ b/drivers/firmware/arm_scmi/transports/virtio.c @@ -870,6 +870,9 @@ static int scmi_vio_probe(struct virtio_device *vdev) /* Ensure initialized scmi_vdev is visible */ smp_store_mb(scmi_vdev, vdev);
+ /* Set device ready */ + virtio_device_ready(vdev); + ret = platform_driver_register(&scmi_virtio_driver); if (ret) { vdev->priv = NULL;