From: Jan Weitzel <J.Weitzel@phytec.de>
To: Evgeniy Polyakov <zbr@ioremap.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC] w1: Disable irqs in critical section
Date: Thu, 08 Sep 2011 07:46:21 +0200 [thread overview]
Message-ID: <1315460781.4396.10.camel@lws-weitzel> (raw)
In-Reply-To: <20110907175059.GA12074@ioremap.net>
Am Mittwoch, den 07.09.2011, 21:50 +0400 schrieb Evgeniy Polyakov:
> On Wed, Sep 07, 2011 at 10:48:32AM +0200, Jan Weitzel (j.weitzel@phytec.de) wrote:
> > Interrupting w1_delay in w1_read_bit results in missing the low level
> > on the w1 line and receiving "1" instead of "0".
> > Adding local_irq_save / local_irq_restore around the critical section
>
> This means that CPU will be essentially stuck for 15 useconds for every
> bit transferred, doesn't really look like a good idea.
>
> Are you absolutely sure that missing bit is because of timings and not
> some other bug?
>
I trigger a gpio line after the samplepoint. I case of a wrong bit the
sample is taken after the "0 gap". The cycle time (samplt to sample)is
increased form about 80µs to 95µs.
I did the measurement with the w1-gpio driver on a OMAP4 board.
Jan
next prev parent reply other threads:[~2011-09-08 5:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-07 8:48 Jan Weitzel
2011-09-07 17:50 ` Evgeniy Polyakov
2011-09-08 5:46 ` Jan Weitzel [this message]
2011-09-13 22:41 ` Andrew Morton
2011-09-14 12:23 ` Jan Weitzel
2011-09-14 19:45 ` Evgeniy Polyakov
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