On 11 February 2015 at 13:27, Stephen Boyd [off-list ref] wrote:

On 02/10, Ashwin Chaugule wrote:

quoted

Hi Stephen,

On 10 February 2015 at 20:05, Stephen Boyd [off-list ref] wrote:

quoted

Scorpion supports a set of local performance monitor event
selection registers (LPM) sitting behind a cp15 based interface
that extend the architected PMU events to include Scorpion CPU
and Venum VFP specific events. To use these events the user is
expected to program the lpm register with the event code shifted
into the group they care about and then point the PMNx event at
that region+group combo by writing a LPMn_GROUPx event. Add
support for this hardware.

Note: the raw event number is a pure software construct that
allows us to map the multi-dimensional number space of regions,
groups, and event codes into a flat event number space suitable
for use by the perf framework.

This is based on code originally written by Ashwin Chaugule and
Neil Leeder [1] massed to become similar to the Krait PMU support
code.

Thanks for taking this up!
Overall this series looks good to me, but from what I faintly
recollect, doesn't this (and the Krait pmu code) get affected by
powercollapse issues anymore?
e.g.
https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/arch/arm/kernel/perf_event_msm.c?h=msm-3.4&id=b5ca687960f0fea2f4735e83ca5c9543474c19de

Right now there isn't any power collapse support in mainline so
there's no immediate problem. Once we add power collapse support
(i.e. cpuidle) to the Scorpion and Krait platforms we'll need to
do something in the perf event code to properly maintain the
counts across idle. I imagine it would be done by registering for
cpu_pm notifications and then doing the save/restore on
CPU_PM_ENTER and CPU_PM_EXIT. At least, that's what you started
doing in this patch[1]. And then it seems the patch you mention
came after that and actually did the save/restore of the counts.

[1] https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?h=msm-3.4&id=464983a7e991a484cac0bc0885cee4fee318d659

Right. Thats essential whenever the power collapse stuff goes in.

Thanks,
Ashwin.
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