We write 0 to device_status to initiate reset of a virtio-mmio device. The reset operation itself may or may not be completed by the time write instruction completes. Add polling device_status to return 0 to ensure reset completion before reinitializing the device. Change-Id: If15d11d090dfd0d4972ad35f49af03e076872413 Signed-off-by: Jianguo Sun <quic_jianguos@xxxxxxxxxxx> Signed-off-by: Sreenad Menon <quic_sreemeno@xxxxxxxxxxx> Signed-off-by: Anant Goel <quic_anantg@xxxxxxxxxxx> --- drivers/virtio/virtio_mmio.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c index 90e784e7b721..cf1a4a3dd35d 100644 --- a/drivers/virtio/virtio_mmio.c +++ b/drivers/virtio/virtio_mmio.c @@ -70,6 +70,7 @@ #include <linux/virtio_config.h> #include <uapi/linux/virtio_mmio.h> #include <linux/virtio_ring.h> +#include <linux/delay.h> @@ -269,6 +270,11 @@ static void vm_reset(struct virtio_device *vdev) /* 0 status means a reset. */ writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); + /* After writing 0 to device_status, the driver MUST wait for a read of + * device_status to return 0 before reinitializing the device. + */ + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) + msleep(1); } -- 2.17.1
