[PATCH v3 2/3] lib: sbi: Detect Smstateen CSRs at boot-time

[Anup Patel]

On Wed, Apr 6, 2022 at 10:28 PM Mayuresh Chitale
<mchitale at ventanamicro.com> wrote:
>
> Extend HART feature detection to discover Smstateen CSRs at boot-time
> and configure mstateen envcfg bit depending on availability of
> menvcfg CSR.
>
> Signed-off-by: Mayuresh Chitale <mchitale at ventanamicro.com>

Looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  include/sbi/sbi_hart.h |  4 +++-
>  lib/sbi/sbi_hart.c     | 25 +++++++++++++++++++++++++
>  2 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 57f80bc..be3ad9f 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -28,9 +28,11 @@ enum sbi_hart_features {
>         SBI_HART_HAS_AIA = (1 << 5),
>         /** HART has menvcfg CSR */
>         SBI_HART_HAS_MENVCFG = (1 << 6),
> +       /** HART has mstateen CSR **/
> +       SBI_HART_HAS_SMSTATEEN = (1 << 7),
>
>         /** Last index of Hart features*/
> -       SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_MENVCFG,
> +       SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_SMSTATEEN,
>  };
>
>  struct sbi_scratch;
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 6be9286..b0edf38 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -43,6 +43,7 @@ static void mstatus_init(struct sbi_scratch *scratch)
>         int cidx;
>         unsigned int num_mhpm = sbi_hart_mhpm_count(scratch);
>         uint64_t mhpmevent_init_val = 0;
> +       uint64_t mstateen_val;
>
>         /* Enable FPU */
>         if (misa_extension('D') || misa_extension('F'))
> @@ -87,6 +88,22 @@ static void mstatus_init(struct sbi_scratch *scratch)
>  #endif
>         }
>
> +       if (sbi_hart_has_feature(scratch, SBI_HART_HAS_SMSTATEEN)) {
> +               mstateen_val = csr_read(CSR_MSTATEEN0);
> +#if __riscv_xlen == 32
> +               mstateen_val |= ((uint64_t)csr_read(CSR_MSTATEEN0H)) << 32;
> +#endif
> +               mstateen_val |= SMSTATEEN_STATEN;
> +               if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MENVCFG))
> +                       mstateen_val |= SMSTATEEN0_HSENVCFG;
> +               else
> +                       mstateen_val &= ~SMSTATEEN0_HSENVCFG;
> +               csr_write(CSR_MSTATEEN0, mstateen_val);
> +#if __riscv_xlen == 32
> +               csr_write(CSR_MSTATEEN0H, mstateen_val >> 32);
> +#endif
> +       }
> +
>         if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MENVCFG)) {
>                 menvcfg_val = csr_read(CSR_MENVCFG);
>
> @@ -348,6 +365,9 @@ static inline char *sbi_hart_feature_id2string(unsigned long feature)
>         case SBI_HART_HAS_MENVCFG:
>                 fstr = "menvcfg";
>                 break;
> +       case SBI_HART_HAS_SMSTATEEN:
> +               fstr = "smstateen";
> +               break;
>         default:
>                 break;
>         }
> @@ -584,6 +604,11 @@ __aia_skip:
>         if (!trap.cause)
>                 hfeatures->features |= SBI_HART_HAS_MENVCFG;
>
> +       /* Detect if hart supports mstateen CSRs */
> +       val = csr_read_allowed(CSR_MSTATEEN0, (unsigned long)&trap);
> +       if (!trap.cause)
> +               hfeatures->features |= SBI_HART_HAS_SMSTATEEN;
> +
>         return;
>  }
>
> --
> 2.17.1
>
>
> --
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