[v2] i2c: s3c2410: dont need CPU_FREQ transitions for exynos series

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@samsung.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(-)

On Tue, Oct 15, 2013 at 3:23 PM, Naveen Krishna Chatradhi
<ch.naveen@samsung.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@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.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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Hi,

On Mon, Oct 14, 2013 at 11:56 PM, Kyungmin Park <kmpark@infradead.org> wrote:
> On Tue, Oct 15, 2013 at 3:23 PM, Naveen Krishna Chatradhi
> <ch.naveen@samsung.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@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.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(-)

Looks great to me.  Thank you for the suggestions Tomasz, as always.

Reviewed-by: Doug Anderson <dianders@chromium.org>

We need to come up with a solution for the CPU_FREQ stuff in
s3c2410_wdt too.  We could use a similar solution but since the
CPU_FREQ stuff in s3c2410_wdt is more than just an optimization it
means that it's not good if S3C24XX is included in a multiplatform
kernel.  (For the watchdog it's more than just an optimization since
every frequency transition actually pets the watchdog, making it
useless when you transition several times per second).

-Doug
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