[PATCH 09/11] lib: sbi: Detect hart features only once for each hart

[Atish Patra]

On Fri, Apr 29, 2022 at 8:52 AM Anup Patel <apatel at ventanamicro.com> wrote:
>
> Currently, the hart_detect_features() is called everytime a hart
> is stopped and started again which is unnecessary work.
>
> We update hart_detect_features() to detect hart features only
> once for each hart.
>

Great.

> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> ---
>  lib/sbi/sbi_hart.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 956d185..28a7e75 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -28,6 +28,7 @@ extern void __sbi_expected_trap_hext(void);
>  void (*sbi_hart_expected_trap)(void) = &__sbi_expected_trap;
>
>  struct hart_features {
> +       bool detected;
>         int priv_version;
>         unsigned long extensions;
>         unsigned int pmp_count;
> @@ -510,11 +511,15 @@ static int hart_pmu_get_allowed_bits(void)
>  static void hart_detect_features(struct sbi_scratch *scratch)
>  {
>         struct sbi_trap_info trap = {0};
> -       struct hart_features *hfeatures;
> +       struct hart_features *hfeatures =
> +               sbi_scratch_offset_ptr(scratch, hart_features_offset);
>         unsigned long val, oldval;
>
> -       /* Reset hart features */
> -       hfeatures = sbi_scratch_offset_ptr(scratch, hart_features_offset);
> +       /* If hart features already detected then do nothing */
> +       if (hfeatures->detected)
> +               return;
> +
> +       /* Clear hart features */
>         hfeatures->extensions = 0;
>         hfeatures->pmp_count = 0;
>         hfeatures->mhpm_count = 0;
> @@ -642,6 +647,9 @@ __mhpm_skip:
>                         hfeatures->extensions |= BIT(SBI_HART_EXT_SMSTATEEN);
>         }
>
> +       /* Mark hart feature detection done */
> +       hfeatures->detected = true;
> +
>         return;
>  }
>
> --
> 2.34.1
>

Reviewed-by: Atish Patra <atishp at rivosinc.com>

-- 
Regards,
Atish