[RFT PATCH v1 3/5] usb: Add some delay to wait for slow USB devices to be operational

Marek Vasut
2020-03-22T13:29:11Z

On 3/22/20 2:00 PM, Lukasz Majewski wrote:
> This change provides some extra time for some slow (or degraded) USB devices
> to become fully operational.
>
> This code is the port to newest U-Boot of the fix from - "rayvt" (from [1]).
>
> Links:
> [1] - https://forum.doozan.com/read.php?3,35295,35295#msg-35295
> [2] - https://www.dropbox.com/s/nrkrd1no63viuu8/uboot-bodhi-2016.05-timeoutTD.patch?dl=0
>
> Signed-off-by: Lukasz Majewski <lukma@denx.de>
> [Unfortunately, the original patch [2] did not contain S-o-B from the original
> author - "rayvt"]
> ---
>
> common/usb.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/common/usb.c b/common/usb.c
> index 349e838f1d..305482b5bb 100644
> --- a/common/usb.c
> +++ b/common/usb.c
> @@ -925,14 +925,20 @@ static int get_descriptor_len(struct usb_device *dev, int len, int expect_len)
> __maybe_unused struct usb_device_descriptor *desc;
> ALLOC_CACHE_ALIGN_BUFFER(unsigned char, tmpbuf, USB_BUFSIZ);
> int err;
> + int retry = 5;
>
> desc = (struct usb_device_descriptor *)tmpbuf;
>
> +again:
> err = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, len);
> if (err < expect_len) {
> if (err < 0) {
> - printf("unable to get device descriptor (error=%d)\n",
> - err);
> + printf("unable to get device descriptor (error=%d) retry: %d\n",
> + err, retry);
> + mdelay(50);

Why 50 mSec and not some other value, like 100 mSec ?