From: Mark Brown <broonie@kernel.org>
To: Max Filippov <jcmvbkbc@gmail.com>
Cc: "linux-xtensa@linux-xtensa.org" <linux-xtensa@linux-xtensa.org>,
linux-spi@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Chris Zankel <chris@zankel.net>, Marc Gauthier <marc@cadence.com>,
Rob Herring <robh+dt@kernel.org>,
Grant Likely <grant.likely@linaro.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/3] spi: add xtfpga SPI controller driver
Date: Wed, 12 Mar 2014 01:53:42 +0000 [thread overview]
Message-ID: <20140312015342.GL28112@sirena.org.uk> (raw)
In-Reply-To: <CAMo8BfL6dwgZitRBZQEU6HCRVMRoYhPkiJWW5QTpS-cu-njR5A@mail.gmail.com>
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On Wed, Mar 12, 2014 at 05:43:49AM +0400, Max Filippov wrote:
> On Wed, Mar 12, 2014 at 5:08 AM, Mark Brown <broonie@kernel.org> wrote:
> > That's buggy, drivers should never configure anything more than 8 bits
> > per word with regmap.
> Ok, so the driver should allow for 8 bit transfers and regmap will arrange
> transfers as 8-bit pairs, making CS to be asserted for 16 bits, right?
> Hmmm... I see the only way to support that with that hardware: advertise
> 8 bit support, buffer bytes up to 16 bits, send 16 bit words on CS deassertion
> request, log violations verbosely. Other ideas?
That's about it. Like I keep saying for any sort of generic use you
really want to support 8 bits per word.
> > You're missing the point. The controller chip select line can do what
> > it likes, it's not connected to the target device if a GPIO is being
> > used.
> In my case SPI controller is wired directly to the codec with three
> wires: SDIN, SCLK and CS. There are no registers that can control
> either of these wires independently of others.
Right, but other users are likely to exist and the framework has support
for this so it's not much work to support.
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next prev parent reply other threads:[~2014-03-12 1:53 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-11 12:44 [PATCH 0/3] xtensa " Max Filippov
2014-03-11 12:44 ` [PATCH 1/3] spi: add " Max Filippov
2014-03-11 19:49 ` Mark Brown
2014-03-11 20:20 ` Max Filippov
2014-03-12 0:34 ` Mark Brown
2014-03-12 0:59 ` Max Filippov
2014-03-12 1:08 ` Mark Brown
2014-03-12 1:43 ` Max Filippov
2014-03-12 1:53 ` Mark Brown [this message]
2014-03-12 1:11 ` Mark Brown
2014-03-12 1:48 ` Max Filippov
2014-03-12 13:24 ` Mark Brown
2014-03-11 12:44 ` [PATCH 2/3] spi/xtensa-xtfpga: add DT binding documentation Max Filippov
2014-03-11 12:44 ` [PATCH 3/3] MAINTAINERS: add xtfpga platform section Max Filippov
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