linux-kernel - Re: [PATCH 2/2] clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940

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Date:   Sat, 29 Jan 2022 13:05:31 -0800
From:   Drew Fustini <dfustini@...libre.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Keerthy <j-keerthy@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Tero Kristo <kristo@...nel.org>, Suman Anna <s-anna@...com>
Subject: Re: [PATCH 2/2] clocksource/drivers/timer-ti-dm: Handle dra7 timer
 wrap errata i940

On Tue, Mar 23, 2021 at 09:43:26AM +0200, Tony Lindgren wrote:
> There is a timer wrap issue on dra7 for the ARM architected timer.
> In a typical clock configuration the timer fails to wrap after 388 days.
> 
> To work around the issue, we need to use timer-ti-dm percpu timers instead.
> 
> Let's configure dmtimer3 and 4 as percpu timers by default, and warn about
> the issue if the dtb is not configured properly.

Hi Tony,

This causes a conflict for IPU2 which is using timer 3 and 4.

>From arch/arm/boot/dts/dra7-ipu-dsp-common.dtsi:

  &ipu2 {
          mboxes = <&mailbox6 &mbox_ipu2_ipc3x>;
          ti,timers = <&timer3>;
          ti,watchdog-timers = <&timer4>, <&timer9>;
  };

I noticed an error ("could not get timer platform device") when booting
mainline on a BeagleBoard X15 (AM578):

  omap-rproc 55020000.ipu: assigned reserved memory node ipu2-memory@...00000
  remoteproc remoteproc1: 55020000.ipu is available
  remoteproc remoteproc1: powering up 55020000.ipu
  remoteproc remoteproc1: Booting fw image dra7-ipu2-fw.xem4, size 3747220
  omap-rproc 55020000.ipu: could not get timer platform device
  omap-rproc 55020000.ipu: omap_rproc_enable_timers failed: -19
  remoteproc remoteproc1: can't start rproc 55020000.ipu: -19

I switched this errata fix to use timer 15 and 16 instead which resolves
the error.  Do you think that is an acceptable solution?

If so, I will post the patch to the list.

Thanks,
Drew