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Date:   Wed, 27 May 2020 12:50:58 +0100
From:   Will Deacon <will@kernel.org>
To:     Tuan Phan <tuanphan@os.amperecomputing.com>
Cc:     patches@amperecomputing.com, Mark Rutland <mark.rutland@arm.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2] driver/perf: Add PMU driver for the ARM DMC-620
 memory controller.
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On Mon, May 11, 2020 at 01:44:52PM -0700, Tuan Phan wrote:
> DMC-620 PMU supports 10 total counters that are independently
> programmable for different events and can be individually started and
> stopped.
> 
> ACPI is only supported; device tree support is welcomed to be added and
> tested for other platforms.
> 
> Usage example:
>   #perf stat -e arm_dmc620_10008c000/clk_cycle_count/ -C 0
>   Get perf event for clk_cycle_count counter.
> 
>   #perf stat -e arm_dmc620_10008c000/clkdiv2_allocate,mask=0x1f,match=0x2f,
>   incr=2,invert=1/ -C 0
>   The above example shows how to specify mask, match, incr,
>   invert parameters for clkdiv2_allocate event.
> 
> Signed-off-by: Tuan Phan <tuanphan@os.amperecomputing.com>
> ---
> Changes in v2:
> - Removed IRQF_SHARED flag and added support for multiple 
> PMUs sharing the same interrupt.
> - Fixed an interrupt handler race condition.
> 
> The ACPI binding spec for PMU DMC620 is under beta and located
> in ARM server group under project "ACPI on ARM". 
> 
>  drivers/perf/Kconfig          |   8 +
>  drivers/perf/Makefile         |   1 +
>  drivers/perf/arm_dmc620_pmu.c | 869 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 878 insertions(+)
>  create mode 100644 drivers/perf/arm_dmc620_pmu.c

Given that this is Arm IP, it would be nice to have a review from somebody
at Arm. I have vague recollections of an internal DMC PMU driver too, but I
don't remember the details.

Will