linux-kernel - Re: [PATCH 22/35] W1: ds1wm.c msleep for reset

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Message-ID: <20080330113806.GL15122@2ka.mipt.ru>
Date:	Sun, 30 Mar 2008 15:38:06 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	David Fries <david@...es.net>
Cc:	linux-kernel@...r.kernel.org, Matt Reimer <mreimer@...p.net>
Subject: Re: [PATCH 22/35] W1: ds1wm.c msleep for reset

On Fri, Mar 28, 2008 at 07:27:00AM -0500, David Fries (david@...es.net) wrote:
> masters/ds1wm.c 1.4
> Like the previous w1_io.c reset coments and msleep patch, I don't have
> the hardware to verify the change, but I think it is safe.  It also
> helps to see a comment like this in the code.
> "We'll wait a bit longer just to be sure."
> If they are going to calculate delaying 324.9us, but actually delay
> 500us, why not just give up the CPU and sleep?  This is designed for a
> battery powered ARM system, avoiding busywaiting has to be good for
> battery life.

Ack, but would like to here from Matt Reimer.
Added to Cc:

> I sent a request for testers March 7, 2008 to the Linux kernel mailing
> list and two developers who have patches for ds1wm.c, but I didn't get
> any respons.
> 
> Signed-off-by: David Fries <david@...es.net>
> ---
>  drivers/w1/masters/ds1wm.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/w1/masters/ds1wm.c b/drivers/w1/masters/ds1wm.c
> index ea894bf..29e144f 100644
> --- a/drivers/w1/masters/ds1wm.c
> +++ b/drivers/w1/masters/ds1wm.c
> @@ -160,8 +160,10 @@ static int ds1wm_reset(struct ds1wm_data *ds1wm_data)
>  	 *     625 us - 60 us - 240 us - 100 ns = 324.9 us
>  	 *
>  	 * We'll wait a bit longer just to be sure.
> +	 * Was udelay(500), but if it is going to busywait the cpu that long,
> +	 * might as well come back later.
>  	 */
> -	udelay(500);
> +	msleep(1);
>  
>  	ds1wm_write_register(ds1wm_data, DS1WM_INT_EN,
>  		DS1WM_INTEN_ERBF | DS1WM_INTEN_ETMT | DS1WM_INTEN_EPD |
> -- 
> 1.4.4.4



-- 
	Evgeniy Polyakov
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