On Mon, Jan 31, 2022 at 12:16:06PM +0200, Tony Lindgren wrote:

Hi,

* Drew Fustini [off-list ref] [220129 21:05]:

quoted

On Tue, Mar 23, 2021 at 09:43:26AM +0200, Tony Lindgren wrote:

quoted

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.

quoted

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@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 :)

I ran this with existing errata fix with dmtimer 3 and 4:

root@am57xx-evm:~# cyclictest --mlockall --smp --priority=80 --interval=200 --distance=0
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.02 0.03 0.05 

T: 0 ( 1449) P:80 I:200 C: 800368 Min:      0 Act:   32 Avg:   22 Max:     128
T: 1 ( 1450) P:80 I:200 C: 800301 Min:      0 Act:   12 Avg:   23 Max:      70

And the results after my switch to dmtimer 15 and 16:

root@am57xx-evm:~# cyclictest --mlockall --smp --priority=80 --interval=200 --distance=0
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.36 0.19 0.07

T: 0 ( 1711) P:80 I:200 C: 759599 Min:      0 Act:    6 Avg:   22 Max:     108
T: 1 ( 1712) P:80 I:200 C: 759539 Min:      0 Act:   19 Avg:   23 Max:      79

This doesn't appear to show any latency regression.

Any other options for cyclictest that that you'd recommend trying?

Thank you,
Drew

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