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

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Date:	Sun, 30 Mar 2008 08:43:27 -0500
From:	David Fries <david@...es.net>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	linux-kernel@...r.kernel.org, Matt Reimer <mreimer@...p.net>
Subject: Re: [PATCH 22/35] W1: ds1wm.c msleep for reset

On Sun, Mar 30, 2008 at 03:38:06PM +0400, Evgeniy Polyakov wrote:
> 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:

Yes, it would be nice to hear from someone with the hardware, but it
has been over three weeks without a response.

Date:   Fri, 7 Mar 2008 22:37:37 -0600
Subject: [W1] ds1wm: testers please, msleep not udelay
Cc: Anton Vorontsov <cbouatmailru@...il.com>,
        Matt Reimer <mreimer@...p.net>


> > 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

-- 
David Fries <david@...es.net>
http://fries.net/~david/ (PGP encryption key available)
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