[PATCH] riscv: dts: allwinner: d1: Add PMU event node

[Inochi Amaoto]

The DT field of riscv,pmu for opensbi can be found on:
https://github.com/riscv-software-src/opensbi/blob/master/docs/pmu_support.md

The value can be found in the R1S0 version of C906 documentation:
https://dl.linux-sunxi.org/D1/Xuantie_C906_R1S0_User_Manual.pdf

The meaning of T-HEAD events can be found in this patch:
https://lore.kernel.org/linux-perf-users/IA1PR20MB4953DD82D0116EC291C21777BBE2A@IA1PR20MB4953.namprd20.prod.outlook.com

The patch above also provides documentation for T-HEAD events and a example
that shows how to use perf with T-HEAD events.

>On Sat, Aug 26, 2023 at 04:38:53PM +0800, Inochi Amaoto wrote:
>> D1 has several pmu events supported by opensbi.
>> These events can be used by perf for profiling.
>>
>> Signed-off-by: Inochi Amaoto <inochiama at outlook.com>
>
>Could you please include a link to some documentation as to where these
>values came from? I know several people have had some trouble with
>understanding the pmu DT stuff & having some documentation would make
>this an in-tree end-to-end example.
>
>Thanks,
>Conor.
>