[PATCH v5 04/15] lib: sbi: Detect number of bits implemented in mhpmcounter

[Anup Patel]

On Sat, Jul 10, 2021 at 9:48 PM Atish Patra <atish.patra at wdc.com> wrote:
>
> RISC-V privilege specification allows the implementation to have less
> than 64 bits.
>
> Add a function to detect the number of implemented bits in mhpmcounter
> dynamically at runtime.
>
> Reviewed-by: Xiang W <wxjstz at 126.com>
> 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 |  1 +
>  lib/sbi/sbi_hart.c     | 48 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)
>
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 9e317c52008c..0c18ef9325b2 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -44,6 +44,7 @@ void sbi_hart_delegation_dump(struct sbi_scratch *scratch,
>  unsigned int sbi_hart_pmp_count(struct sbi_scratch *scratch);
>  unsigned long sbi_hart_pmp_granularity(struct sbi_scratch *scratch);
>  unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch);
> +unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch);
>  int sbi_hart_pmp_configure(struct sbi_scratch *scratch);
>  bool sbi_hart_has_feature(struct sbi_scratch *scratch, unsigned long feature);
>  void sbi_hart_get_features_str(struct sbi_scratch *scratch,
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 9c01cf75c0bb..e8cd0421b5e6 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -33,6 +33,7 @@ struct hart_features {
>         unsigned int pmp_addr_bits;
>         unsigned long pmp_gran;
>         unsigned int mhpm_count;
> +       unsigned int mhpm_bits;
>  };
>  static unsigned long hart_features_offset;
>
> @@ -177,6 +178,14 @@ unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch)
>         return hfeatures->pmp_addr_bits;
>  }
>
> +unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch)
> +{
> +       struct hart_features *hfeatures =
> +                       sbi_scratch_offset_ptr(scratch, hart_features_offset);
> +
> +       return hfeatures->mhpm_bits;
> +}
> +
>  int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
>  {
>         struct sbi_domain_memregion *reg;
> @@ -330,6 +339,37 @@ static unsigned long hart_pmp_get_allowed_addr(void)
>         return val;
>  }
>
> +static int hart_pmu_get_allowed_bits(void)
> +{
> +       unsigned long val = ~(0UL);
> +       struct sbi_trap_info trap = {0};
> +       int num_bits = 0;
> +
> +       /**
> +        * It is assumed that platforms will implement same number of bits for
> +        * all the performance counters including mcycle/minstret.
> +        */
> +       csr_write_allowed(CSR_MHPMCOUNTER3, (ulong)&trap, val);
> +       if (!trap.cause) {
> +               val = csr_read_allowed(CSR_MHPMCOUNTER3, (ulong)&trap);
> +               if (trap.cause)
> +                       return 0;
> +       }
> +       num_bits = __fls(val) + 1;
> +#if __riscv_xlen == 32
> +       csr_write_allowed(CSR_MHPMCOUNTER3H, (ulong)&trap, val);
> +       if (!trap.cause) {
> +               val = csr_read_allowed(CSR_MHPMCOUNTER3H, (ulong)&trap);
> +               if (trap.cause)
> +                       return num_bits;
> +       }
> +       num_bits += __fls(val) + 1;
> +
> +#endif
> +
> +       return num_bits;
> +}
> +
>  static void hart_detect_features(struct sbi_scratch *scratch)
>  {
>         struct sbi_trap_info trap = {0};
> @@ -395,9 +435,17 @@ __pmp_skip:
>
>         /* Detect number of MHPM counters */
>         __check_csr(CSR_MHPMCOUNTER3, 0, 1UL, mhpm_count, __mhpm_skip);
> +       hfeatures->mhpm_bits = hart_pmu_get_allowed_bits();
> +
>         __check_csr_4(CSR_MHPMCOUNTER4, 0, 1UL, mhpm_count, __mhpm_skip);
>         __check_csr_8(CSR_MHPMCOUNTER8, 0, 1UL, mhpm_count, __mhpm_skip);
>         __check_csr_16(CSR_MHPMCOUNTER16, 0, 1UL, mhpm_count, __mhpm_skip);
> +
> +       /**
> +        * No need to check for MHPMCOUNTERH for RV32 as they are expected to be
> +        * implemented if MHPMCOUNTER is implemented.
> +        */
> +
>  __mhpm_skip:
>
>  #undef __check_csr_64
> --
> 2.31.1
>
>
> --
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