linux-kernel - Re: [PATCH] clocksource: dw_apb_timer

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Date:	Fri, 30 Oct 2015 11:44:46 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Jisheng Zhang <jszhang@...vell.com>, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] clocksource: dw_apb_timer_of: support timer-based delay

On 10/30/2015 09:27 AM, Jisheng Zhang wrote:
> Implement an ARM delay timer to be used for udelay(). This allows us to
> skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD
> platforms. And after this patch, udelay() will be unaffected by CPU
> frequency changes.
>
> Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> ---
>   drivers/clocksource/Kconfig           | 10 ++++++++++
>   drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++
>   2 files changed, 26 insertions(+)
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index a7726db..7b081805 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -29,6 +29,16 @@ config DW_APB_TIMER_OF
>   	select DW_APB_TIMER
>   	select CLKSRC_OF
>
> +config DW_APB_TIMER_BASED_DELAY
> +	bool "DW APB timer based delay"
> +	depends on ARM && DW_APB_TIMER_OF
> +	default n
> +	help
> +	  This option enables support for using the DW APB timer to
> +	  implement timer-based delay. It is useful for skiping the
> +	  delay loop calibration at boot on some platforms. And the
> +	  udelay() will be unaffected by CPU frequency changes.
> +

Why do you want it to be optional ?

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