[PATCH v5 02/15] lib: sbi: Detect mcountinihibit support at runtime

[Anup Patel]

On Sat, Jul 10, 2021 at 9:48 PM Atish Patra <atish.patra at wdc.com> wrote:
>
> RISC-V ISA specification v1.11 defined mcountinhibit CSR that allows
> software to stop any counter from incrementing. The SBI PMU extension
> depends on this CSR support in hardware.
>
> Define mcountinhibit as a hart specific feature and detect it at runtime.
>
> Reviewed-by: Anup Patel <anup.patel at wdc.com>
> Signed-off-by: Atish Patra <atish.patra at wdc.com>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  include/sbi/sbi_hart.h |  4 +++-
>  lib/sbi/sbi_hart.c     | 11 +++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 031c7b08a815..9e317c52008c 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -18,8 +18,10 @@ enum sbi_hart_features {
>         SBI_HART_HAS_SCOUNTEREN = (1 << 0),
>         /** Hart has M-mode counter enable */
>         SBI_HART_HAS_MCOUNTEREN = (1 << 1),
> +       /** Hart has counter inhibit CSR */
> +       SBI_HART_HAS_MCOUNTINHIBIT = (1 << 2),
>         /** HART has timer csr implementation in hardware */
> -       SBI_HART_HAS_TIME = (1 << 2),
> +       SBI_HART_HAS_TIME = (1 << 3),
>
>         /** Last index of Hart features*/
>         SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_TIME,
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 56878b47624e..0bd1db1ab85e 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -259,6 +259,9 @@ static inline char *sbi_hart_feature_id2string(unsigned long feature)
>         case SBI_HART_HAS_MCOUNTEREN:
>                 fstr = "mcounteren";
>                 break;
> +       case SBI_HART_HAS_MCOUNTINHIBIT:
> +               fstr = "mcountinhibit";
> +               break;
>         case SBI_HART_HAS_TIME:
>                 fstr = "time";
>                 break;
> @@ -421,6 +424,14 @@ __mhpm_skip:
>                         hfeatures->features |= SBI_HART_HAS_MCOUNTEREN;
>         }
>
> +       /* Detect if hart supports MCOUNTINHIBIT feature */
> +       val = csr_read_allowed(CSR_MCOUNTINHIBIT, (unsigned long)&trap);
> +       if (!trap.cause) {
> +               csr_write_allowed(CSR_MCOUNTINHIBIT, (unsigned long)&trap, val);
> +               if (!trap.cause)
> +                       hfeatures->features |= SBI_HART_HAS_MCOUNTINHIBIT;
> +       }
> +
>         /* Detect if hart supports time CSR */
>         csr_read_allowed(CSR_TIME, (unsigned long)&trap);
>         if (!trap.cause)
> --
> 2.31.1
>
>
> --
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