On 3/23/20 8:04 AM, Lukasz Majewski wrote: > Hi Marek, > >> 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 <lu...@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 ? > > I think that this value (50 ms) was took from Linux in some point and > with the retry set to 5 was the ported heuristics. > > If you ask why exactly there is 50 ms - I cannot say, as I've just > ported the patch.
I see, then please research this. The USB stack has enough ad-hoc random values in it already, no need to add new ones.
