On Mon, May 09, 2022 at 11:02:23AM +0100, Suzuki K Poulose wrote:

Cc: Mike Williams, Mathieu Poirier

On 09/05/2022 10:28, Will Deacon wrote:

quoted

On Sun, May 08, 2022 at 07:28:08PM -0500, Besar Wicaksono wrote:

quoted

Add driver support for ARM CoreSight PMU device and event attributes for NVIDIA
implementation. The code is based on ARM Coresight PMU architecture and ACPI ARM
Performance Monitoring Unit table (APMT) specification below:
  * ARM Coresight PMU:
         https://developer.arm.com/documentation/ihi0091/latest
  * APMT: https://developer.arm.com/documentation/den0117/latest

Notes:
  * There is a concern on the naming of the PMU device.
    Currently the driver is probing "arm-coresight-pmu" device, however the APMT
    spec supports different kinds of CoreSight PMU based implementation. So it is
    open for discussion if the name can stay or a "generic" name is required.
    Please see the following thread:
    http://lists.infradead.org/pipermail/linux-arm-kernel/2022-May/740485.html

Besar Wicaksono (2):
   perf: coresight_pmu: Add support for ARM CoreSight PMU driver
   perf: coresight_pmu: Add support for NVIDIA SCF and MCF attribute

  arch/arm64/configs/defconfig                  |    1 +
  drivers/perf/Kconfig                          |    2 +
  drivers/perf/Makefile                         |    1 +
  drivers/perf/coresight_pmu/Kconfig            |   10 +
  drivers/perf/coresight_pmu/Makefile           |    7 +
  .../perf/coresight_pmu/arm_coresight_pmu.c    | 1317 +++++++++++++++++
  .../perf/coresight_pmu/arm_coresight_pmu.h    |  147 ++
  .../coresight_pmu/arm_coresight_pmu_nvidia.c  |  300 ++++
  .../coresight_pmu/arm_coresight_pmu_nvidia.h  |   17 +
  9 files changed, 1802 insertions(+)

How does this interact with all the stuff we have under
drivers/hwtracing/coresight/?

Absolutely zero, except for the name. The standard
is named "CoreSight PMU" which is a bit unfortunate,
given the only link, AFAIU, with the "CoreSight" architecture
is the Lock Access Register(LAR). For reference, the
drivers/hwtracing/coresight/ is purely "CoreSight" self-hosted
tracing and the PMU is called "cs_etm" (expands to coresight etm).
Otherwise the standard doesn't have anything to do with what
exists already in the kernel.

That said, I am concerned that the "coresight_pmu" is easily confused
with what exists today. Given that this is more of a "PMU" standard
for the IPs in the Arm world, it would be better to name it as such
avoiding any confusion with the existing PMUs.

Thanks Suzuki. I did suggest something similar[1] but asked to retain it
so that it can be discussed in the bigger and right forum.

One potential recommendation for the name is, "Arm PMU"  (The ACPI table is
named Arm PMU Table). But then that could be clashing with the armv8_pmu
:-(.

Some of the other options are :

"Arm Generic PMU"
"Arm Uncore PMU"

I wasn't sure on this if there is any restriction on usage of this on Arm
and hence didn't make the suggestion. But if allowed, this would be my
choice too.

-- 
Regards,
Sudeep

[1] https://lore.kernel.org/lkml/20220504182633.a3mwuiohfqtjvpep@bogus (local)

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