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

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Message-ID: <CAHfPSqCHUAccv4Usd1XcZ8MzD+Jf=jHSWWQ0m1Mj64nKCN7_jw@mail.gmail.com>
Date:	Sat, 12 Oct 2013 12:06:34 +0530
From:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>, sjg@...omium.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, wsa@...-dreams.de,
	khali@...ux-fr.org, Ben Dooks <ben-linux@...ff.org>,
	grant.likely@...retlab.ca, broonie@...nel.org,
	dianders@...omium.org, cpgs@...sung.com
Subject: Re: [PATCH] i2c: s3c2410: dont need CPU_FREQ transitions for exynos series

On 12 October 2013 11:12, Tomasz Figa <t.figa@...sung.com> wrote:
> On Saturday 12 of October 2013 04:28:51 Tomasz Figa wrote:
>> [Fixing incorrent mail addresses and dropping the old DT ML.]
>>
>> On Saturday 12 of October 2013 04:22:04 Tomasz Figa wrote:
>> > Hi Naveen,
>> >
>> > On Friday 11 of October 2013 16:56:54 Naveen Krishna Chatradhi wrote:
>> > > The exynos5 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 for non Exynos SoCs.
>> > >
>> > > This change should save a bunch of cpufreq transitions calls
>> > > which does not apply to exynos SoCs.
>> >
>> > The idea is fine, although...
>> >
>> > > Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
>> > > ---
>> > >  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..d062fa7 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) && !defined(CONFIG_ARCH_EXYNOS)
>> >
>> > ...this is not a good coding practice, especially when already having
>> > multiplatform kernels in sight.
>> >
>> > The best way would be to check on which SoC we are running at runtime,
>> > but since this might need changing a lot of code, then at least I would
>> > change this from !defined(EXYNOS) to defined(S3C24XX), so it is not being
>> > compiled in when S3C24XX support is not enabled and if it's enabled then
>> > the notifier will be registered as a safe fallback that will run correctly
>> > on all platforms.
>
> Actually you can simply check for CONFIG_CPU_FREQ_S3C24XX here.
sure, this makes it more meaningful. will make the modifications and resubmit.
>
> Best regards,
> Tomasz
>



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