linux-kernel - Re: [PATCH v4] spi: qup: Add DMA capabilities

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Message-ID: <54FC30BE.1070606@metafoo.de>
Date:	Sun, 08 Mar 2015 12:21:34 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Mark Brown <broonie@...nel.org>
CC:	Stanimir Varbanov <stanimir.varbanov@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-spi@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Kumar Gala <galak@...eaurora.org>,
	Andy Gross <agross@...eaurora.org>,
	Sagar Dharia <sdharia@...eaurora.org>,
	Daniel Sneddon <dsneddon@...eaurora.org>
Subject: Re: [PATCH v4] spi: qup: Add DMA capabilities

On 03/07/2015 08:43 PM, Andy Shevchenko wrote:
> On Sat, Mar 7, 2015 at 1:21 PM, Mark Brown <broonie@...nel.org> wrote:
>> On Wed, Mar 04, 2015 at 12:02:05PM +0200, Stanimir Varbanov wrote:
>>> From: Andy Gross <agross@...eaurora.org>
>>>
>>> This patch adds DMA capabilities to the spi-qup driver.  If DMA channels are
>>> present, the QUP will use DMA instead of block mode for transfers to/from SPI
>>> peripherals for transactions larger than the length of a block.
>>
>> Applied, but why is there no devm_dma_request_slave_channel_reason()?
>
> I suppose the answer would be "we have a lot of slightly different
> cases and we have to get rid of current mess with legacy API calls".
> The most problematic stuff now inside DMA slave subsystem is so called
> "filter function". It's a main impediment right now as I understand.

dma_request_slave_channel_reason() is the sane API though and does not use 
the filter functions. Adding a devm version of it seems reasonable.

- Lars
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