[PATCH v3] console: usb: kbd: Limit poll frequency to improve performance

Filip Žaludek filip.zaludek at oracle.com
Thu Feb 9 22:18:56 CET 2023


On 2/8/23 19:45, Michal Suchánek wrote:
> Hello,
> On Wed, Jan 18, 2023 at 05:01:12PM +0100, Filip Žaludek wrote:
>> Hi Michal,
>>   thanks for testing! Do you consider keyboard as working once it is detected without
>> 'usb_kbd usb_kbd: Timeout poll on interrupt endpoint', or judging from subsequent
>> typing? Note that issue is reproducible only in about 20% of reboots.
> I rely on keyboard input to boot so if it was 20% broken I would notice.
> I don't use the rPi all that much so if it was broken only a few
> % of the time there is a chance I would miss it.

Common denominator here is most likely dwc2 controller on RPi3.

> However, for me not typing on the keyboard during usb detection it is
> 100% not detected, typing on it during usb detection it is 100%
> detected.

There are 3 states:
Keyboard not detected, keyboard detected but does not work, keyboard detected and works.

If keyboard is not detected/does not work then subsequent grub timeout is misleading/pointless..

> The timeout is limitation of the dwc2 controller handling of usb hubs.

  Michal, can you please elaborate more [pointers to docs, discussions] why/how is the timeout
limitation of the dwc2 controller handling of usb hubs?
  I am trying to dissect it more by printing single character from myriad of places what actually
works as a workaround, but when substituting with mdelay(x) exceeding printing does not.
[common/usb.c, common/usb_hub.c, drivers/core/device.c, drivers/usb/host/dwc2.c, drivers/usb/host/usb-uclass.c]


> There might be a possibility to improve the driver so that it handles
> the condition but it might be that the Linux driver relies on a separate
> thread handling the controller which is not acceptable for u-boot.
> I am not usb expert and definitely not dwc2 expert so I cannot do more
> than workaround the current driver limitation.
>> For me I can always enter 'U-Boot>' shell, but then keyboard usually does not work.
>> And yes, resetting the usb controller with pressing a key afterwards will
>> finally break the keyboard. ('usb reset' typed from keyboard)
>> If you are Prague located I am ready to demonstrate what I am talking about.
>>   Simon's keyboard detection is somewhat interfered by 'SanDisk USB Extreme Pro' detection,
>> printed complaints but keyboard still works..
>> 'usb_kbd usb_kbd: Timeout poll on interrupt endpoint' and 'Failed to get keyboard state from device 0c40:8000'
>> Btw. why from 0c40:8000 (ELMCU 2.4GHz receiver) when wired keyboard is 046d:c31c (Logitech Keyboard K120)?
>>   What is supposed scenario for RPi3/u-boot/grub usb keyboard equipped users wanting to boot non-default?
>> Enter 'U-Boot>' shell to detect keyboard; type boot; select desired grub entry..?
>> Reverting either from the two makes it non issue for me:
>> 'dwc2: use the nonblock argument in submit_int_msg'
>> commit 9dcab2c4d2cb50ab1864c818b82a72393c160236
> Without this booting from USB is not feasible because reading every
> block from the USB drive waits for the keyboard to time out.
>> 'console: usb: kbd: Limit poll frequency to improve performance'
>> commit 96991e652f541323a03c5b7e075d54a117091618
> No idea about this one, for me it doea not give any substantial
> difference in behavior.
> Thanks
> Michal

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