[v1 1/2] lib: sbi_pmu: Add PMU snapshot definitions

[Anup Patel]

On Wed, Dec 6, 2023 at 6:39 AM Atish Patra <atishp at rivosinc.com> wrote:
>
> OpenSBI doesn't support SBI PMU snapshot yet as there is not much benefit
> unless the multiple counters overflow at the same time.
>
> Just add the definition and return not supported error at this moment. The
> default returned error is also not supported. Thus, no functional change
> intended.
>
> Signed-off-by: Atish Patra <atishp at rivosinc.com>
> ---
>  include/sbi/sbi_ecall_interface.h | 3 +++
>  lib/sbi/sbi_ecall_pmu.c           | 2 ++
>  2 files changed, 5 insertions(+)
>
> diff --git a/include/sbi/sbi_ecall_interface.h b/include/sbi/sbi_ecall_interface.h
> index 1fe469e37078..b4e6f63e0bf0 100644
> --- a/include/sbi/sbi_ecall_interface.h
> +++ b/include/sbi/sbi_ecall_interface.h
> @@ -103,6 +103,7 @@
>  #define SBI_EXT_PMU_COUNTER_STOP       0x4
>  #define SBI_EXT_PMU_COUNTER_FW_READ    0x5
>  #define SBI_EXT_PMU_COUNTER_FW_READ_HI 0x6
> +#define SBI_EXT_PMU_SNAPSHOT_SET_SHMEM 0x7
>
>  /** General pmu event codes specified in SBI PMU extension */
>  enum sbi_pmu_hw_generic_events_t {
> @@ -241,9 +242,11 @@ enum sbi_pmu_ctr_type {
>
>  /* Flags defined for counter start function */
>  #define SBI_PMU_START_FLAG_SET_INIT_VALUE (1 << 0)
> +#define SBI_PMU_START_FLAG_INIT_FROM_SNAPSHOT (1 << 1)
>
>  /* Flags defined for counter stop function */
>  #define SBI_PMU_STOP_FLAG_RESET (1 << 0)
> +#define SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT (1 << 1)
>
>  /* SBI function IDs for DBCN extension */
>  #define SBI_EXT_DBCN_CONSOLE_WRITE             0x0
> diff --git a/lib/sbi/sbi_ecall_pmu.c b/lib/sbi/sbi_ecall_pmu.c
> index 1d5d512eeed7..c58591106d09 100644
> --- a/lib/sbi/sbi_ecall_pmu.c
> +++ b/lib/sbi/sbi_ecall_pmu.c
> @@ -74,6 +74,8 @@ static int sbi_ecall_pmu_handler(unsigned long extid, unsigned long funcid,
>         case SBI_EXT_PMU_COUNTER_STOP:
>                 ret = sbi_pmu_ctr_stop(regs->a0, regs->a1, regs->a2);
>                 break;
> +       case SBI_EXT_PMU_SNAPSHOT_SET_SHMEM:
> +               /* fallthrough as OpenSBI doesn't support snapshot yet */

We should also return SBI_ERR_NO_SHMEM when:
1) SBI_PMU_START_FLAG_INIT_FROM_SNAPSHOT is set in PMU start call
2) SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT is set in PMU stop call.

>         default:
>                 ret = SBI_ENOTSUPP;
>         }
> --
> 2.34.1
>

Regards,
Anup