linux-kernel - Re: [PATCH] i2c-s3c2410: Decrease delay after end of transaction

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Message-ID: <20100420111314.GD2234@trinity.fluff.org>
Date:	Tue, 20 Apr 2010 12:13:14 +0100
From:	Ben Dooks <ben-linux@...ff.org>
To:	Yauhen Kharuzhy <yauhen.kharuzhy@...mwad.com>
Cc:	Ben Dooks <ben-linux@...ff.org>, Jean Delvare <khali@...ux-fr.org>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH] i2c-s3c2410: Decrease delay after end of transaction

On Tue, Apr 20, 2010 at 01:53:19PM +0300, Yauhen Kharuzhy wrote:
> msleep(1) which has been used for delay after issuing a STOP condition
> to bus cause very big delay (min 1/HZ s). This is makes bulk register
> update in I2C devices (for instance video camera) very slowly.
> 
> Seems that this delay can be safely decreased to few tens of
> microseconds.

Mark Brown has already submitted a similar patch that uses the bus
busy bit. will be in the i2c-next tree soon.
 
> Signed-off-by: Yauhen Kharuzhy <yauhen.kharuzhy@...mwad.com>
> ---
>  drivers/i2c/busses/i2c-s3c2410.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
> index d27072b..de20a4e 100644
> --- a/drivers/i2c/busses/i2c-s3c2410.c
> +++ b/drivers/i2c/busses/i2c-s3c2410.c
> @@ -521,7 +521,7 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
>  
>  	/* ensure the stop has been through the bus */
>  
> -	msleep(1);
> +	udelay(50);
>  
>   out:
>  	return ret;
> -- 
> 1.6.6.1
> 

-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.

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