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

[Tony Lindgren]

Hi,

* Drew Fustini <dfustini at baylibre.com> [220129 21:05]:
> 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>;
>   };

OK, sorry I missed that part.

> 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 at 95800000
>   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?

I think the only difference is that timers 15 and 16 are in l4_per3 instead
of l4_per1. I doubt that matters as they are pretty much always clocked in
this case. If you want to check you can run cyclictest :)

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

OK thanks,

Tony