[PATCH v21 4/4] perf: arm_pmuv3: Add support for the Branch Record Buffer Extension (BRBE)

[James Clark]

On 19/05/2025 10:56 pm, Rob Herring wrote:
> On Mon, May 19, 2025 at 04:06:22PM +0100, Will Deacon wrote:
>> Hey Rob,
>>
>> On Mon, Apr 07, 2025 at 12:41:33PM -0500, Rob Herring (Arm) wrote:
>>> From: Anshuman Khandual <anshuman.khandual at arm.com>
>>>
>>> The ARMv9.2 architecture introduces the optional Branch Record Buffer
>>> Extension (BRBE), which records information about branches as they are
>>> executed into set of branch record registers. BRBE is similar to x86's
>>> Last Branch Record (LBR) and PowerPC's Branch History Rolling Buffer
>>> (BHRB).
>>
>> Since you picked this up from v19, the driver has changed considerably
>> and I presume you will be continuing to extend it in future as the
>> architecture progresses. Perhaps having you listed as Author (and
>> crucially, in git blame :p) with Anshuman as a Co-developed-by: would be
>> more appropriate?
> 
> Shrug.
> 
>>> ---
>>>   drivers/perf/Kconfig         |  11 +
>>>   drivers/perf/Makefile        |   1 +
>>>   drivers/perf/arm_brbe.c      | 802 +++++++++++++++++++++++++++++++++++++++++++
>>>   drivers/perf/arm_brbe.h      |  47 +++
>>>   drivers/perf/arm_pmu.c       |  15 +-
>>>   drivers/perf/arm_pmuv3.c     | 129 ++++++-
>>>   include/linux/perf/arm_pmu.h |   8 +
>>>   7 files changed, 1006 insertions(+), 7 deletions(-)
>>
>> Do you know if James Clark's tests [1] are going to be respun for the
>> perf tool? It would be handy to have some way to test this new
>> functionality.
> 
> Yes. I dropped them here because I've been told by Arnaldo in the past
> to send userspace stuff separately.
> 

That version of the test was out of date so I've pushed the new version 
here: 
https://git.linaro.org/plugins/gitiles/people/james.clark/linux.git/+/16e4a18c2d5fc53736f05c9052b1d11d74909707

But I'll wait for the driver changes to be finalised before posting it. 
Or Rob can take it back into the patchset.