linux-kernel - Re: [PATCH v2] clocksource/drivers/riscv: Get rid of clocksource_arch

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Date:   Tue, 3 Jan 2023 11:38:55 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Prabhakar <prabhakar.csengg@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-riscv@...ts.infradead.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2] clocksource/drivers/riscv: Get rid of
 clocksource_arch_init() callback

On 12/29/22 16:46, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Having a clocksource_arch_init() callback always sets vdso_clock_mode to
> VDSO_CLOCKMODE_ARCHTIMER if GENERIC_GETTIMEOFDAY is enabled, this is
> required for the riscv-timer.
> 
> This works for platforms where just riscv-timer clocksource is present.
> On platforms where other clock sources are available we want them to
> register with vdso_clock_mode set to VDSO_CLOCKMODE_NONE.
> 
> On the Renesas RZ/Five SoC OSTM block can be used as clocksource [0], to
> avoid multiple clock sources being registered as VDSO_CLOCKMODE_ARCHTIMER
> move setting of vdso_clock_mode in the riscv-timer driver instead of doing
> this in clocksource_arch_init() callback as done similarly for ARM/64
> architecture.
> 
> [0] drivers/clocksource/renesas-ostm.c
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Tested-by: Samuel Holland <samuel@...lland.org>
> ---
> RFC -> v2
> * Dropped vdso_default static global variable
> * Used IS_ENABLED() macro
> * Included Tested-by from Samuel
> 
> RFC:
> https://patchwork.kernel.org/project/linux-renesas-soc/patch/20221211215843.24024-1-prabhakar.mahadev-lad.rj@bp.renesas.com/
> ---
>  arch/riscv/Kconfig                | 1 -
>  arch/riscv/kernel/time.c          | 9 ---------
>  drivers/clocksource/timer-riscv.c | 5 +++++
>  3 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index e2b656043abf..9c687da7756d 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -12,7 +12,6 @@ config 32BIT
>  
>  config RISCV
>  	def_bool y
> -	select ARCH_CLOCKSOURCE_INIT
>  	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
>  	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
>  	select ARCH_HAS_BINFMT_FLAT
> diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
> index 8217b0f67c6c..42bee305e997 100644
> --- a/arch/riscv/kernel/time.c
> +++ b/arch/riscv/kernel/time.c
> @@ -30,12 +30,3 @@ void __init time_init(void)
>  	of_clk_init(NULL);
>  	timer_probe();
>  }
> -
> -void clocksource_arch_init(struct clocksource *cs)
> -{
> -#ifdef CONFIG_GENERIC_GETTIMEOFDAY
> -	cs->vdso_clock_mode = VDSO_CLOCKMODE_ARCHTIMER;
> -#else
> -	cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
> -#endif
> -}
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 55dad7965f43..c416e5e934bf 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -77,6 +77,11 @@ static struct clocksource riscv_clocksource = {
>  	.mask		= CLOCKSOURCE_MASK(64),
>  	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
>  	.read		= riscv_clocksource_rdtime,
> +#if IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY)
> +	.vdso_clock_mode = VDSO_CLOCKMODE_ARCHTIMER,
> +#else
> +	.vdso_clock_mode = VDSO_CLOCKMODE_NONE,

The else case isn't strictly necessary because VDSO_CLOCKMODE_NONE is
the default. Either way it looks fine to me.

Reviewed-by: Samuel Holland <samuel@...lland.org>

And I tested v2 as well.

Regards,
Samuel

> +#endif
>  };
>  
>  static int riscv_timer_starting_cpu(unsigned int cpu)