linux-kernel - Re: [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for multiple erratum detection methods

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Date:   Wed, 22 Mar 2017 16:41:14 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Scott Wood <oss@...error.net>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Ding Tianhong <dingtianhong@...wei.com>,
        dann frazier <dann.frazier@...onical.com>
Subject: Re: [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for
 multiple erratum detection methods

On Mon, Mar 20, 2017 at 05:48:17PM +0000, Marc Zyngier wrote:
> We're currently stuck with DT when it comes to handling errata, which
> is pretty restrictive. In order to make things more flexible, let's
> introduce an infrastructure that could support alternative discovery
> methods. No change in functionality.
> 
> Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  arch/arm64/include/asm/arch_timer.h  |  7 +++-
>  drivers/clocksource/arm_arch_timer.c | 80 +++++++++++++++++++++++++++++++-----
>  2 files changed, 75 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index b4b34004a21e..5cd964e90d11 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -37,9 +37,14 @@ extern struct static_key_false arch_timer_read_ool_enabled;
>  #define needs_unstable_timer_counter_workaround()  false
>  #endif
>  
> +enum arch_timer_erratum_match_type {
> +	ate_match_dt,
> +};
>  
>  struct arch_timer_erratum_workaround {
> -	const char *id;		/* Indicate the Erratum ID */
> +	enum arch_timer_erratum_match_type match_type;

Putting the match_fn instead will be much more simpler and the code won't
have to deal with ate_match_type, no ?

[ ... ]

> +static void arch_timer_check_ool_workaround(enum arch_timer_erratum_match_type type,
> +					    void *arg)
> +{
> +	const struct arch_timer_erratum_workaround *wa;
> +	ate_match_fn_t match_fn = NULL;
> +
> +	if (static_branch_unlikely(&arch_timer_read_ool_enabled))
> +		return;
> +

Why is this check necessary ?

[ ... ]



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