oprofile and ARM A9 hardware counter

[Måns Rullgård]

Will Deacon <will.deacon at arm.com> writes:

> On Fri, Jan 27, 2012 at 01:47:01PM +0000, Måns Rullgård wrote:
>> Will Deacon <will.deacon at arm.com> writes:
>> 
>> > Mans,
>> >
>> > On Fri, Jan 27, 2012 at 12:56:35PM +0000, Måns Rullgård wrote:
>> >> Will Deacon <will.deacon at arm.com> writes:
>> >> > Did this lead anywhere in the end? It seems as though Ming Lei has a working
>> >> > setup but Stephane is unable to replicate it, despite applying the necessary
>> >> > patches and trying an updated bootloader.
>> >> 
>> >> With the patches listed above plus the one in [1], I get PMU interrupts.
>> >> However, unless I restrict the profiled process to one CPU
>> >> (taskset 1 perf record ...), I get a panic in armpmu_event_update() with
>> >> the 'event' argument being null when called from armv7pmu_handle_irq().
>> >> 
>> >> [1] http://article.gmane.org/gmane.linux.ports.arm.omap/69696
>> >
>> > Great, thanks for trying this out. Which version of the kernel were you
>> > using? I fixed a bunch of NULL pointer derefs. during the 3.2 window, but if
>> > you were using an -rc kernel you have have hit one of them.
>> 
>> This was with the Linaro tilt-3.2 kernel from
>> git://git.linaro.org/landing-teams/working/ti/kernel.git, commit
>> 73e2c294444f209d281f7cd10b52b53b087e74f1.  Maybe one of the many patches
>> it has on top of 3.2 is to blame.
>
> Perhaps, or (more likely) the interrupt affinity for the CTI isn't working
> properly and the interrupt is always delivered to CPU0. I'll keep this in
> mind in case we get any more reports like this.

It works whichever CPU I pin it to (i.e. taskset 2 also works).

FWIW, my /proc/interrupts looks like this when perf is running:

           CPU0       CPU1
 29:   25238127    1409121       GIC  twd
 33:    4586197          0       GIC  arm-pmu
 34:          0    4744550       GIC  arm-pmu
 39:          0          0       GIC  TWL6030-PIH
 41:          0          0       GIC  l3-dbg-irq
 42:          0          0       GIC  l3-app-irq
 43:          0          0       GIC  prcm
 44:        141          0       GIC  DMA
[...]

-- 
Måns Rullgård
mans at mansr.com