oprofile and ARM A9 hardware counter
khilman at ti.com
Tue Apr 3 10:27:52 EDT 2012
Will Deacon <will.deacon at arm.com> writes:
> On Tue, Apr 03, 2012 at 11:01:53AM +0100, Shilimkar, Santosh wrote:
>> On Tue, Apr 3, 2012 at 3:17 PM, Will Deacon <will.deacon at arm.com> wrote:
>> > It seems that they're both needed to get reliable PMU operation. Without the
>> > CLKDM_CAN_SWSUP fix, no interrupts are generated at all. Without the patch
>> > below (), it seems that we don't generate enough. So it looks like we
>> > need them both.
>> I see. Can you please confirm if it is still the case with .
> Right, ignore my previous comment, I was using a vanilla 3.3 kernel without
> realising and therefore what I thought were PMU/CTI interrupts were actually
> just from a timer. Sorry for the confusion.
> So I've gone back to basics. Here is a branch containing what I believe
> should be all the patches required for the OMAP4 PMU:
> git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git perf/omap4
> I've omitted the SWSUSP patch since you say it breaks pm, which is clearly not
> The problem is, trying to boot this on my pandaboard results in a hang (see
> dmesg below). Even worse, the problem isn't easily bisectable since rebuilding
> a working image can give you something that no longer boots and I haven't found
> a reliable way to cause the lockup.
> I'll take JTAG for a whirl to see where we are. If anything looks wrong in
> my dmesg, please shout (there are plenty of things in there that look like
> they've gone awry).
Not sure why it hangs for you, but it worked for me both with your
branch on v3.3 and merging with v3.4-rc1
Below is a Kconfig snippet which I append to my .config after
building omap2plus_defconfig in order to build a perf/trace/PMU enabled
kernel for my Panda.
# perf stat sleep 1
Performance counter stats for 'sleep 1':
9.582520 task-clock # 0.009 CPUs utilized
1 context-switches # 0.104 K/sec
0 CPU-migrations # 0.000 K/sec
147 page-faults # 0.015 M/sec
5096283 cycles # 0.532 GHz
607876 stalled-cycles-frontend # 11.93% frontend cycles idle
3285045 stalled-cycles-backend # 64.46% backend cycles idle
2722485 instructions # 0.53 insns per cycle
# 1.21 stalled cycles per insn
259247 branches # 27.054 M/sec
84274 branch-misses # 32.51% of all branches
1.015919088 seconds time elapsed
CONFIG_ARCH_OMAP3=n # need to disable OMAP3 for CPU_HAS_PMU support, needed for perf on OMAP4
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