[PATCH v6 0/5] cpufreq: powernv: Redesign the presentation of throttle notification and solve bug-fixes in the driver

From: Shilpasri G Bhat
Date: Fri Jan 22 2016 - 02:20:28 EST

In POWER8, OCC(On-Chip-Controller) can throttle the frequency of the
CPU when the chip crosses its thermal and power limits. Currently,
powernv-cpufreq driver detects and reports this event as a console
message. Some machines may not sustain the max turbo frequency in all
conditions and can be throttled frequently. This can lead to the
flooding of console with throttle messages. So this patchset aims to
redesign the presentation of this event via sysfs counters and
tracepoints. And it also fixes couple of bugs reported in the driver.

- Patch [1] fixes the cpu hot-plug bug in powernv_cpufreq_work_fn().
- Patch [2] solves a bug in powernv_cpufreq_throttle_check(), which
calls in to cpu_to_chip_id() in hot path which reads DT every time
to find the chip id.
- Patches [3] to [5] will add a perf trace point
"power:powernv_throttle" and sysfs throttle counter stats in

Changes from v5:
- Fix kbuild error:
drivers/cpufreq/powernv-cpufreq.c:428:2: error: implicit declaration of
function 'get_online_cpus' [-Werror=implicit-function-declaration]

Changes from v4:
- Fix a hot-plug bug in powernv_cpufreq_work_fn()
- Changes wrt Gautham's and Shreyas's comments

Changes from v3:
- Add a fix to replace cpu_to_chip_id() with simpler PIR shift to
obtain the chip id.
- Break patch2 in to two patches separating the tracepoint and sysfs
attribute changes.

Changes from v2:
- Fixed kbuild test warning.
drivers/cpufreq/powernv-cpufreq.c:609:2: warning: ignoring return
value of 'kstrtoint', declared with attribute warn_unused_result

Shilpasri G Bhat (5):
cpufreq: powernv: Hot-plug safe the kworker thread
cpufreq: powernv: Remove cpu_to_chip_id() from hot-path
cpufreq: powernv/tracing: Add powernv_throttle tracepoint
cpufreq: powernv: Replace pr_info with trace print for throttle event
cpufreq: powernv: Add sysfs attributes to show throttle stats

drivers/cpufreq/powernv-cpufreq.c | 313 +++++++++++++++++++++++++++++++-------
include/trace/events/power.h | 22 +++
kernel/trace/power-traces.c | 1 +
3 files changed, 281 insertions(+), 55 deletions(-)