Re: [PATCH v4 1/1] ARM: perf: Set ARMv7 SDER SUNIDEN bit

On Wed, Jan 13, 2016 at 11:36:26PM -0500, George G. Davis wrote:

From: Martin Fuzzey <redacted>

ARMv7 counters other than the CPU cycle counter only work if the Secure
Debug Enable Register (SDER) SUNIDEN bit is set.

Since access to the SDER is only possible in secure state, it will
only be done if the device tree property "secure-reg-access" is set.

Without this:
# perf stat -e cycles,instructions sleep 1

 Performance counter stats for 'sleep 1':

          14606094 cycles                    #    0.000 GHz
                 0 instructions              #    0.00  insns per cycle

After applying:
# perf stat -e cycles,instructions sleep 1

 Performance counter stats for 'sleep 1':

           5843809 cycles
           2566484 instructions              #    0.44  insns per cycle

       1.020144000 seconds time elapsed

Some platforms (eg i.MX53) may also need additional platform specific
setup.

Signed-off-by: Martin Fuzzey <redacted>
Signed-off-by: Pooya Keshavarzi <Pooya.Keshavarzi-V5te9oGctAVWk0Htik3J/w@public.gmane.org>
Signed-off-by: George G. Davis <redacted>
---
Changes in v4:
- Reword commit message to clarify that this change is ARMv7 specific.
- Clarify that secure-reg-access property is only valid for ARMv7 CPUs
  and is not supported on anything else (in particular, the arm64
  port requires you to boot in non-secure mode).
- Convert on_each_cpu(armv7pmu_enable_secure_access, NULL, 1) call in
  armv7pmu_init() to in-lined code in ->reset callback, since that is
  called off the back of a CPU hotplug notifier when the PMU may need
  to be reinitialised.
Changes in v3:
- Pooya Keshavarzi:
  * v2 review comment fixups
  * Use on_each_cpu() to set SUNIDEN on all CPUs
  * Move armv7pmu_enable_secure_access() call from armv7pmu_start() to
    armv7_a8_map_event() such that is called only once instead of each
    time `perf` is executed
- George G. Davis:
  * Fixup to apply after file renames due to commit fa8ad78 (arm: perf:
    factor arm_pmu core out to drivers)
  * Fix checkpatch 'CHECK: Prefer using the BIT macro' issue
---
 Documentation/devicetree/bindings/arm/pmu.txt | 10 ++++++++++

Acked-by: Rob Herring <redacted>

Rob
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