[PATCH] usb: storage: increase init retry count to support lengthy HDD spin up

[Ahmad Fatoum]

Hi,

On 01.03.21 12:07, Ahmad Fatoum wrote:
> Some USB disks take notoriously long to spin up. They are seen by a bus
> scan, but they report ready only after a few seconds have passed. This
> is not a problem if vbus is enabled early on, so devices have had a
> chance to spin up. If vbus is first enabled as part of the usb scan,
> not enough time might have passed for the USB disk to be usable.
> 
> This issue was observed on an i.MX6QP with following topology:
> 
>   usb: USB: scanning bus for devices...
>   usb: 5 USB Device(s) found
>     1 ID 0000:0000
>     |  u-boot EHCI Host Controller
>     |
>     +-2 ID 0424:2517
>     |
>     +-5 ID 1058:2621
>     |    Western Digital Elements 2621
>     ...
> 
> Unplugging and replugging the USB disk and doing a second usb scan
> made the unit ready test succeed. By increasing the retry count
> during initialization, this workaround is no longer necessary.

Please dismiss for now. This doesn't always work, even for my HDD.



> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  drivers/usb/storage/usb.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
> index b417640186a2..7b0aecd757b0 100644
> --- a/drivers/usb/storage/usb.c
> +++ b/drivers/usb/storage/usb.c
> @@ -141,7 +141,7 @@ exit:
>  	return ret;
>  }
>  
> -static int usb_stor_test_unit_ready(struct us_blk_dev *usb_blkdev)
> +static int usb_stor_test_unit_ready(struct us_blk_dev *usb_blkdev, int retries)
>  {
>  	u8 cmd[6];
>  	int ret;
> @@ -150,7 +150,7 @@ static int usb_stor_test_unit_ready(struct us_blk_dev *usb_blkdev)
>  	cmd[0] = SCSI_TST_U_RDY;
>  
>  	ret = usb_stor_transport(usb_blkdev, cmd, sizeof(cmd), NULL, 0,
> -				 10, 100);
> +				 retries, 100);
>  	if (ret < 0)
>  		return -ENODEV;
>  
> @@ -282,7 +282,7 @@ static int usb_stor_blk_io(struct block_device *disk_dev,
>  
>  	/* ensure unit ready */
>  	dev_dbg(dev, "Testing for unit ready\n");
> -	if (usb_stor_test_unit_ready(pblk_dev)) {
> +	if (usb_stor_test_unit_ready(pblk_dev, 10)) {
>  		dev_dbg(dev, "Device NOT ready\n");
>  		return -EIO;
>  	}
> @@ -365,7 +365,8 @@ static int usb_stor_init_blkdev(struct us_blk_dev *pblk_dev)
>  	/* ensure unit ready */
>  	dev_dbg(dev, "Testing for unit ready\n");
>  
> -	result = usb_stor_test_unit_ready(pblk_dev);
> +	/* retry a bit longer than usual as some HDDs take longer to spin up */
> +	result = usb_stor_test_unit_ready(pblk_dev, 60);
>  	if (result) {
>  		dev_dbg(dev, "Device NOT ready\n");
>  		return result;
> 

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