From: Johannes Stezenbach <js@sig21.net>
To: Antony Pavlov <antonynpavlov@gmail.com>
Cc: barebox <barebox@lists.infradead.org>
Subject: Re: SPI chip select problem
Date: Mon, 25 Jun 2012 12:48:59 +0200 [thread overview]
Message-ID: <20120625104859.GA10844@sig21.net> (raw)
In-Reply-To: <CAA4bVAHqT37AuMbBUia4FGSdayQXvSYJ63hok_fYSaZpZHQK6A@mail.gmail.com>
On Mon, Jun 25, 2012 at 02:07:34PM +0400, Antony Pavlov wrote:
> On 25 June 2012 12:53, Johannes Stezenbach <js@sig21.net> wrote:
> > On Mon, Jun 25, 2012 at 11:45:06AM +0400, Antony Pavlov wrote:
> >>
> >> There is the 'cs_change' flag for *_spi_transfer() method, but this
> >> flag does not used at all!
> >
> > altera_spi.c and mic_spi.c use it, but often this is not needed (e.g. for
> > SPI flashes) so to keep the code simple and small it might be better
> > to not implement cs_change handling.
>
> But I have not found any common code where cs_change is managed.
It doesn't need to be handled in common code, the spi_device
driver requests a cs_change if it needs one, the spi_master driver
programs the hardware to do it. Common code in drivers/spi/spi.c
doesn't need to care. (To clarify: cs_change does not mean
to switch from one CS to another, it means to pulse the
CS line between spi_transfers of a spi_message. Some devices
need that in some cases.)
Johannes
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prev parent reply other threads:[~2012-06-25 10:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-25 7:45 Antony Pavlov
2012-06-25 8:53 ` Johannes Stezenbach
2012-06-25 10:07 ` Antony Pavlov
2012-06-25 10:48 ` Johannes Stezenbach [this message]
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