[PATCH v2 0/5] Add support for T-HEAD C9xx PMU extensions

[Atish Patra]

On Wed, Aug 17, 2022 at 4:20 AM Heiko Stuebner <heiko at sntech.de> wrote:
>
> The T-HEAD C9XX cores implement functionality very similar to SSCOFPMF.
> Instead of implementing a separate interface into SBI as done in v1,
> we can add the C9XX tidbits with quite minimal overhead and leaverage
> the existing SBI pmu interface including giving access to the firmware
> counters.
>

That's great. But modifying generic code for a vendor errata is not a
good idea as I pointed out
in the kernel patch as well. Instead of that, can you please define
pmu_ops so that platforms
can override those and have a clean implementation ?

You won't need a HART extension any more. Technically, this is not a
valid extension also.

> The current only hickup is the detection override in sbi_hart, where
> I still need to find out why the MHPMCOUNTERs are not writeable
> at _that_ point of the boot, but with this series on top of openSBI 1.1
> and the matching kernel perf patch I get reasonable results for example
> for:
>
> perf stat -e cycles -e instructions -e L1-icache-load-misses -e L1-icache-loads ls
>
>  Performance counter stats for 'ls':
>
>           17119496      cycles
>            2867765      instructions              #    0.17  insn per cycle
>              55929      L1-icache-load-misses     #    1.61% of all L1-icache accesses
>            3467346      L1-icache-loads
>
>        0.030156216 seconds time elapsed
>
>        0.000000000 seconds user
>        0.023496000 seconds sys
>
> Heiko Stuebner (5):
>   lib: sbi_platform: pass extension bitmap pointer to extension_init
>   lib: sbi: do platform-specific extension population earlier
>   platform: generic: add extensions_init handler and platform-override
>   platform: generic: allwinner: add an extension for C9xx cores
>   lib: sbi_pmu: add t-head pmu support
>
>  include/sbi/riscv_thead_c9xx.h               | 127 +++++++++++++++++++
>  include/sbi/sbi_hart.h                       |   3 +
>  include/sbi/sbi_platform.h                   |   7 +-
>  lib/sbi/sbi_hart.c                           |  29 ++++-
>  lib/sbi/sbi_pmu.c                            |  48 ++++++-
>  platform/generic/allwinner/sun20i-d1.c       |  10 ++
>  platform/generic/include/platform_override.h |   2 +
>  platform/generic/platform.c                  |   9 ++
>  8 files changed, 226 insertions(+), 9 deletions(-)
>  create mode 100644 include/sbi/riscv_thead_c9xx.h
>
> --
> 2.35.1
>
>
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-- 
Regards,
Atish