linux-kernel - Re: [PATCH v2] i2c: s3c2410: dont need CPU

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Date:	Tue, 15 Oct 2013 15:56:27 +0900
From:	Kyungmin Park <kmpark@...radead.org>
To:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>
Cc:	linux-i2c@...r.kernel.org, t.figa@...sung.com, sjg@...omium.org,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	wsa@...-dreams.de, ben-linux@...ff.org, grant.likely@...retlab.ca,
	broonie@...nel.org, dianders@...omium.org, cpgs@...sung.com
Subject: Re: [PATCH v2] i2c: s3c2410: dont need CPU_FREQ transitions for
 exynos series

On Tue, Oct 15, 2013 at 3:23 PM, Naveen Krishna Chatradhi
<ch.naveen@...sung.com> wrote:
> For Exynos4 and Exynos5 SoCs from Samsung the i2c clock is based
> on a fixed 66 MHz peripheral clock, and therefore is completely
> independent of the cpu frequency.
> Thus, registering for a CPU freq notifier is very wasteful.
>
> This patch modifes the code such that, i2c bus registers to
> cpu_freq_transition only if CONFIG_CPU_FREQ_S3C24XX is enabled.
>
> This change should save a bunch of cpufreq transitions calls
> which does not apply to exynos SoCs.
>
> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> ---
> Changes since v1:
> Use CONFIG_CPU_FREQ_S3C24XX instead of (CONFIG_CPU_FREQ & !CONFIG_EXYNOS)
> As commented by Tomasz
>
>  drivers/i2c/busses/i2c-s3c2410.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
> index cab1c91..97f14f7 100644
> --- a/drivers/i2c/busses/i2c-s3c2410.c
> +++ b/drivers/i2c/busses/i2c-s3c2410.c
> @@ -123,7 +123,7 @@ struct s3c24xx_i2c {
>         struct s3c2410_platform_i2c     *pdata;
>         int                     gpios[2];
>         struct pinctrl          *pctrl;
> -#ifdef CONFIG_CPU_FREQ
> +#if defined(CONFIG_CPU_FREQ_S3C24XX)
>         struct notifier_block   freq_transition;
>  #endif
>  };
> @@ -843,7 +843,7 @@ static int s3c24xx_i2c_clockrate(struct s3c24xx_i2c *i2c, unsigned int *got)
>         return 0;
>  }
>
> -#ifdef CONFIG_CPU_FREQ
> +#if defined(CONFIG_CPU_FREQ_S3C24XX)
>
>  #define freq_to_i2c(_n) container_of(_n, struct s3c24xx_i2c, freq_transition)
>
> --
> 1.7.10.4
>
> --
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