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

Wed May 3 03:28:06 CEST 2023

Hi Filip,

On Tue, 2 May 2023 at 12:43, Filip Žaludek <filip.zaludek at oracle.com> wrote:
>
>
>
> Hi Simon, Michal, Marek,
>
>
>
> On 4/26/23 03:04, Simon Glass wrote:
> > Hi Filip,
> >
> > On Tue, 25 Apr 2023 at 06:36, Filip Žaludek <filip.zaludek at oracle.com> wrote:
> >>
> >>
> >>
> >> Hi Simon,
> >>
> >>
> >> On 4/19/23 03:49, Simon Glass wrote:
> >>> Hi Filip,
> >>>
> >>> On Tue, 11 Apr 2023 at 14:24, Filip Žaludek <filip.zaludek at oracle.com> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On 2/8/23 20:01, Mark Kettenis wrote:
> >>>>>> 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.
>
>
>
> More updates to usb keyboard/RPi3/dwc2 controller issue:
>
>    I was following my former observation about printing characters from semi
> random places [usb.c, usb_hub.c, device.c, usb-uclass.c, dwc2.c] what
> works as workaround. I realized this is only when printing to vidconsole,
> not to serial. After disabling video_sync() and/or flush_dcache_range()
> from corresponding vidconsole print functions, printing is no longer
> workaround. This behavior seem to be due to cache coherency.
>
>
>
>   Do you have any objections against elephant in porcelain proposal?
> Not able to narrow it down more to single source code line.
> With this keyboard works for me even when touching it only during 15s grub timeout.
> It is not for sure that cache coherency problem is from dwc2, but afaik there
> are no other complaints to usb keyboard.
> Performance degradation not observed..
>
>
> %< -------------------------------------------------------------
> diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
> index 23060fc369..f95314ff1b 100644
> --- a/drivers/usb/host/dwc2.c
> +++ b/drivers/usb/host/dwc2.c
> @@ -814,6 +814,7 @@ static int dwc_otg_submit_rh_msg(struct dwc2_priv *priv, struct usb_device *dev,
>          else
>                  stat = dwc_otg_submit_rh_msg_out(priv, dev, buffer, txlen, cmd);
>
> +       flush_dcache_all();
>          mdelay(1);

We have dma_map_single() and dma_unmap_single() which are designed for
this. If you put these into the two functions that are called
immediately above, perhaps that will solve the problem.

>
>          return stat;
> %< -------------------------------------------------------------
>
>
>
>
>
> >>>>
> >>>>
> >>>> Hello,
> >>>>      I am about to dig more into this issue with proper tools, but failed to
> >>>> configure/compile trace functionality on RPi3 due to missing references
> >>>> to timer_early_get_count() and timer_early_get_rate().
> >>>
> >>> You could implement a proper timer driver for rpi.
> >>>
> >>>>
> >>>>     Is it possible/feasible to implement calls in CONFIG_SYS_ARCH_TIMER
> >>>> and/or CONFIG_SP804_TIMER?
> >>>
> >>> Yes
> >>
> >>
> >>    I am little bit missing here secret sauce, timer_early_get_count() and timer_early_get_rate()
> >> are not supposed to be implemented in arch/arm/cpu/armv8/generic_timer.c? But predestined for
> >> drivers/timer/sp804_timer.c?
> >>
> >> TIMER is required for common/board_f.c and common/board_r.c but it disables generic_timer..
> >> %< -----------------------------------------
> >> ifndef CONFIG_$(SPL_TPL_)TIMER
> >> obj-$(CONFIG_SYS_ARCH_TIMER) += generic_timer.o
> >> endif
> >> %< -----------------------------------------
> >> And obviously multiple definition of get_tbclk and get_ticks when forced to compile/link.
> >
> > It seems from the above that if TIMER is enabled for a particular
> > U-Boot build phase, then generic_timer is not, and vice versa. I
> > suppose that is fair enough.
>
>
>   Sorry, it was imprecisely formulated question from me. I was expecting answer
> confirming and advocating sp804 is superior to System Timer. Implementing
> EARLY_TIMER for System Timer is trivial, sp804 requires research from my side.
> Skimming TF-A project sp804 seems superior.

Yes, implementing that as a timer driver seems fine to me. But we
often have multiple drivers so I suppose some people will use the
generic one if sp804 is not available.

> >>>>
> >>>>     I would be grateful even for trace to generate function traces without
> >>>> timestamps. Is such nasty hack without timestamping supposed to work?
> >>>> Basically my intention is to trace 'usb reset'.
> >>>>
> >>>> Appreciate any hints/outlines how to proceed.
> >>>
> >>> I assume you mean CONFIG_TRACE. Yes, you could update it to support
> >>> writing a zero timestamp. See the add_ftrace() function.
> >>>
> >>> But better to add a driver if you can. It should not be difficult.
> >>>
> >>> Regards,
> >>> Simon
> >>
> >>    I am already happily timestamp tracing with borrowed functionality from generic_timer.c,
> >> albeit bypassing kbuild mechanism. It did not yet answered my usb polling questions,
> >> tracing report is polluted/overfilled.
> >>
> >>
> >>
> >> Instrumenting code thoughts:
> >> * It would be handy to -finstrument-functions only for desired objects.
> >
> > The compiler probably doesn't support that, or at least we don't
> > support passing different compiler args to each file in U-Boot, other
> > than by manually hacking the Makefiles.
> >
> > But I wonder if we could have a list of wildcards to match against the
> > function names?
> >
> >> * It would be handy to have macro inverse to 'notrace' to mark only desired functions. Feasible?
> >> * gcc -finstrument-functions-exclude-file-list still pollutes tracing buffer.
> >
> > I wonder why? You could check whether the filename includes a full
> > path, or something like that, so that it doesn't match. There will be
> > a reason.
> >
>
>
>   Please take my Instrumenting code comments with grain of salt, only as user report.
> Some doc pages track suggestions and whishlists how to make life easier..

Sure...people using a feature are always going to have ways to tidy it
up / improve it. So I encourage you to take a look.

> >>
> >> More Tracing in U-Boot thoughts:
> >> * There is proftool options discrepancy, documented {-c, -f, -m, -o, -t, -v}, implemented {-m, -p, -t, -v}.
> >> * Both types FUNCF_ENTRY and FUNCF_EXIT are marked as " <- " by proftool.
> >
> > Yes, please send a patch or two to clean these up.
> >
> > Regards,
> > Simon
>
>
> I will try to allocate spare time cycles to work on this, albeit with low priority.

OK

Regards,
Simon