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

[Mark Kettenis]

> Date: Wed, 8 Feb 2023 19:45:36 +0100
> From: Michal Suchánek <msuchanek at suse.de>
> 
> 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.
> 
> 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.
> 
> The timeout is limitation of the dwc2 controller handling of usb hubs.
> 
> 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.

Reverting that commit leads to a significant slowdown loading a kernel
from disk with a usb keyboard connected.  The slowdown is somewhat
hardware dependent but on some systems loading the OpenBSD/arm64
kernel would take minutes instead of seconds.