[PATCH] usb: Add 1ms delay after first Get Descriptor request

[Marek Vasut]

On 10/31/22 20:27, Simon Glass wrote:
> Hi Marek,

Hi,

> On Sun, 30 Oct 2022 at 16:38, Marek Vasut <marex at denx.de> wrote:
>>
>> Logitech Unifying Receiver 046d:c52b bcdDevice 12.10 seems
>> sensitive about the first Get Descriptor request. If there
>> are any other requests in the same microframe, the device
>> reports bogus data, first of the descriptor parts is not
>> sent to the host. Wait over one microframe duration before
>> issuing subsequent requests to avoid probe failure with
>> this device, since it can be used to connect USB keyboards.
>>
>> Signed-off-by: Marek Vasut <marex at denx.de>
>> ---
>> Cc: Janne Grunau <j at jannau.net>
>> Cc: Mark Kettenis <kettenis at openbsd.org>
>> ---
>>   common/usb.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
> 
> Is this device complying with the spec or is it broken?
> 
> In any case we need a way to enable/disable this as it will slow down
> unaffected platforms.

This makes little difference, since anyone can plug such device into a 
port and suddenly the platform is affected. We cannot really predict 
what users have on their desks.

Specifically for this case, the logitech receiver seems to be a rather 
common device.

> I've also been wondering if (not with this patch) USB can move to
> using the cyclic stuff to do its work, so we don't have to wait.

EHCI HCD already partly does, at least for storage, so yes, patches welcome.