[RFC PATCH 10/10] lib: Remove redundant sbi_platform_ipi_clear() calls

[Atish Patra]

On Sun, Feb 21, 2021 at 12:54 AM Anup Patel <anup.patel at wdc.com> wrote:
>
> The sbi_platform_ipi_clear() called from wait_for_coldboot() and
> sbi_hsm_hart_wait() is redundant because IPI will be automatically
> cleared by sbi_platform_ipi_init() called from sbi_ipi_init().
>
> Further, wait_for_coldboot() is common for warm startup and warm
> resume path so the sbi_platform_ipi_clear() called in warm resume
> path cause resuming HART to miss an IPI injected other HART to
> wakeup the HART.
>
> Signed-off-by: Anup Patel <anup.patel at wdc.com>
> ---
>  lib/sbi/sbi_hsm.c  |  7 ++++---
>  lib/sbi/sbi_init.c | 11 ++++++++---
>  lib/sbi/sbi_ipi.c  |  5 ++++-
>  3 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/lib/sbi/sbi_hsm.c b/lib/sbi/sbi_hsm.c
> index b597265..643eba0 100644
> --- a/lib/sbi/sbi_hsm.c
> +++ b/lib/sbi/sbi_hsm.c
> @@ -107,7 +107,6 @@ void sbi_hsm_prepare_next_jump(struct sbi_scratch *scratch, u32 hartid)
>  static void sbi_hsm_hart_wait(struct sbi_scratch *scratch, u32 hartid)
>  {
>         unsigned long saved_mie;
> -       const struct sbi_platform *plat = sbi_platform_ptr(scratch);
>         struct sbi_hsm_data *hdata = sbi_scratch_offset_ptr(scratch,
>                                                             hart_data_offset);
>         /* Save MIE CSR */
> @@ -124,8 +123,10 @@ static void sbi_hsm_hart_wait(struct sbi_scratch *scratch, u32 hartid)
>         /* Restore MIE CSR */
>         csr_write(CSR_MIE, saved_mie);
>
> -       /* Clear current HART IPI */
> -       sbi_platform_ipi_clear(plat, hartid);
> +       /*
> +        * No need to clear IPI here because the sbi_ipi_init() will
> +        * clear it for current HART via sbi_platform_ipi_init().
> +        */
>  }
>
>  int sbi_hsm_init(struct sbi_scratch *scratch, u32 hartid, bool cold_boot)
> diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
> index 1d4a838..4de2dfa 100644
> --- a/lib/sbi/sbi_init.c
> +++ b/lib/sbi/sbi_init.c
> @@ -130,7 +130,6 @@ static unsigned long coldboot_done;
>  static void wait_for_coldboot(struct sbi_scratch *scratch, u32 hartid)
>  {
>         unsigned long saved_mie, cmip;
> -       const struct sbi_platform *plat = sbi_platform_ptr(scratch);
>
>         /* Save MIE CSR */
>         saved_mie = csr_read(CSR_MIE);
> @@ -167,8 +166,14 @@ static void wait_for_coldboot(struct sbi_scratch *scratch, u32 hartid)
>         /* Restore MIE CSR */
>         csr_write(CSR_MIE, saved_mie);
>
> -       /* Clear current HART IPI */
> -       sbi_platform_ipi_clear(plat, hartid);
> +       /*
> +        * The wait for coldboot is common for both warm startup and
> +        * warm resume path so clearing IPI here would result in losing
> +        * an IPI in warm resume path.
> +        *
> +        * Also, the sbi_platform_ipi_init() called from sbi_ipi_init()
> +        * will automatically clear IPI for current HART.
> +        */
>  }
>
>  static void wake_coldboot_harts(struct sbi_scratch *scratch, u32 hartid)
> diff --git a/lib/sbi/sbi_ipi.c b/lib/sbi/sbi_ipi.c
> index a3a6ce6..b50735e 100644
> --- a/lib/sbi/sbi_ipi.c
> +++ b/lib/sbi/sbi_ipi.c
> @@ -230,7 +230,10 @@ int sbi_ipi_init(struct sbi_scratch *scratch, bool cold_boot)
>         ipi_data = sbi_scratch_offset_ptr(scratch, ipi_data_off);
>         ipi_data->ipi_type = 0x00;
>
> -       /* Platform init */
> +       /*
> +        * Initialize platform IPI support. This will also clear any
> +        * pending IPIs for current/calling HART.
> +        */
>         ret = sbi_platform_ipi_init(sbi_platform_ptr(scratch), cold_boot);
>         if (ret)
>                 return ret;
> --
> 2.25.1
>
>
> --
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Reviewed-by: Atish Patra <atish.patra at wdc.com>

-- 
Regards,
Atish