From: Mark Brown <broonie@kernel.org>
To: Bert Vermeulen <bert@biot.com>
Cc: ralf@linux-mips.org, linux-mips@linux-mips.org,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
andy.shevchenko@gmail.com, jogo@openwrt.org
Subject: Re: [PATCH v6] spi: Add SPI driver for Mikrotik RB4xx series boards
Date: Thu, 9 Apr 2015 22:50:47 +0100 [thread overview]
Message-ID: <20150409215047.GE6023@sirena.org.uk> (raw)
In-Reply-To: <5526EFA0.2010108@biot.com>
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On Thu, Apr 09, 2015 at 11:31:12PM +0200, Bert Vermeulen wrote:
> On 04/06/2015 06:39 PM, Mark Brown wrote:> On Mon, Apr 06, 2015 at
> > I queried this on a previous version and asked for the code to be better
> > documented...
> I documented it in the commit message:
I'm asking for the *code* to be better documented. Right now it's just
raising obvious questions which are at best going to cost people time
digging for the reasons.
> The m25p80-compatible boot flash and (some models) MMC use regular SPI,
> bitbanged as required by the SoC. However the SPI-connected CPLD has
> a "fast write" mode, in which two bits are transferred by SPI clock
> cycle. The second bit is transmitted with the SoC's CS2 pin.
> Protocol drivers using this fast write facility signal this by setting
> the cs_change flag on transfers.
> The cs_change flag is used here instead of the openwrt version's
> spi_transfer.fast_write flag. The CPLD driver sets this flag on a
> per-transfer basis.
No, this is broken - it's abusing a standard API in a way that's
completly incompatible with the meaning of that API which is obviously a
very bad idea, especially since good practice is to offload the
implementation of that standard API to the core. It *sounds* like
you're just trying to implement two wire mode which does have a standard
API, please use that.
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next prev parent reply other threads:[~2015-04-09 21:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-06 1:54 Bert Vermeulen
2015-04-06 9:56 ` Andy Shevchenko
2015-04-06 16:39 ` Mark Brown
2015-04-09 21:31 ` Bert Vermeulen
2015-04-09 21:50 ` Mark Brown [this message]
2015-04-10 15:31 ` Bert Vermeulen
2015-04-10 15:45 ` Mark Brown
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