linux-kernel - Re: [PATCH V2] clocksource: riscv: Patch riscv_clock_next

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Date:   Thu, 2 Feb 2023 09:39:14 +0530
From:   Anup Patel <anup@...infault.org>
To:     Matt Evans <mev@...osinc.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Atish Patra <atishp@...osinc.com>,
        Palmer Dabbelt <palmer@...belt.com>
Subject: Re: [PATCH V2] clocksource: riscv: Patch riscv_clock_next_event()
 jump before first use

On Thu, Feb 2, 2023 at 1:19 AM Matt Evans <mev@...osinc.com> wrote:
>
> A static key is used to select between SBI and Sstc timer usage in
> riscv_clock_next_event(), but currently the direction is resolved
> after cpuhp_setup_state() is called (which sets the next event).  The
> first event will therefore fall through the sbi_set_timer() path; this
> breaks Sstc-only systems.  So, apply the jump patching before first
> use.
>
> Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
> Signed-off-by: Matt Evans <mev@...osinc.com>

Looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>
> V1 -> V2: Commit msg tweak.
>
>  drivers/clocksource/timer-riscv.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 969a552da8d2..a36d173fd6cd 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>                 return error;
>         }
>
> +       if (riscv_isa_extension_available(NULL, SSTC)) {
> +               pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> +               static_branch_enable(&riscv_sstc_available);
> +       }
> +
>         error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>                          "clockevents/riscv/timer:starting",
>                          riscv_timer_starting_cpu, riscv_timer_dying_cpu);
> @@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>                 pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
>                        error);
>
> -       if (riscv_isa_extension_available(NULL, SSTC)) {
> -               pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> -               static_branch_enable(&riscv_sstc_available);
> -       }
> -
>         return error;
>  }
>
> --
> 2.30.2
>
>