linux-kernel - Re: [PATCH 5/5] RFC spi: sun4i: add DMA support

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Message-ID: <CAMuHMdVThvtqgFnyqoqypwwf1d81uu9NBo6-heTZBcvBxRevNw@mail.gmail.com>
Date:	Mon, 30 May 2016 14:11:51 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Michal Suchanek <hramrach@...il.com>,
	linux-sunxi <linux-sunxi@...glegroups.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>,
	linux-spi <linux-spi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] RFC spi: sun4i: add DMA support

Hi Mark,

On Mon, May 30, 2016 at 1:26 PM, Mark Brown <broonie@...nel.org> wrote:
> On Thu, May 26, 2016 at 07:25:25PM -0000, Michal Suchanek wrote:
>>  - fallback to previous behaviour when DMA initialization fails
>>
>>    + this has the problem that when the driver happens to load before the dma
>>      driver it will not use dma - can be addressed with a module parameter
>
> No, you should pay attention to the error you are getting and let probe
> deferral happen if that's the error you get.

Unfortunately DMA is an optional feature.

There's no way to distinguish between -EPROBE_DEFER due to the SPI master
driver being probed before the DMA engine driver, and -EPROBE_DEFER due to
support for the DMA engine not having been compiled in.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds