From: Junnan Wu Date: Tue, 12 Aug 2025 07:53:43 +0000 (+0800) Subject: firmware: arm_scmi: Mark VirtIO ready before registering scmi_virtio_driver X-Git-Tag: v6.18-rc1~145^2~12^2~7 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e8faa8a466f61f4ae07069ed6b0872f602f1cba9;p=thirdparty%2Fkernel%2Flinux.git firmware: arm_scmi: Mark VirtIO ready before registering scmi_virtio_driver 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 Message-Id: <20250812075343.3201365-1-junnan01.wu@samsung.com> Signed-off-by: Sudeep Holla --- diff --git a/drivers/firmware/arm_scmi/transports/virtio.c b/drivers/firmware/arm_scmi/transports/virtio.c index cb934db9b2b4a..326c4a93e44b9 100644 --- a/drivers/firmware/arm_scmi/transports/virtio.c +++ b/drivers/firmware/arm_scmi/transports/virtio.c @@ -871,6 +871,9 @@ 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;