linux-kernel - Re: [PATCH 1/2] spi: sun4i: add DMA support

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Message-ID: <20160306214206.GW8418@lukather>
Date:	Sun, 6 Mar 2016 22:42:06 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	Mark Brown <broonie@...nel.org>, Priit Laes <plaes@...es.org>,
	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 Mailing List <linux-kernel@...r.kernel.org>,
	Emilio López <emilio@...pez.com.ar>
Subject: Re: [PATCH 1/2] spi: sun4i: add DMA support

On Fri, Feb 26, 2016 at 01:51:51PM +0100, Michal Suchanek wrote:
> Hello,
> 
> On 26 February 2016 at 13:25, Mark Brown <broonie@...nel.org> wrote:
> > On Fri, Feb 26, 2016 at 07:56:56AM +0200, Priit Laes wrote:
> >> From: Emilio López <emilio@...pez.com.ar>
> >>
> >> This patch adds support for 64 byte or bigger transfers on the
> >> sun4i SPI controller. Said transfers will be performed via DMA.
> >>
> >> Signed-off-by: Emilio López <emilio@...pez.com.ar>
> >> Tested-by: Michal Suchanek <hramrach@...il.com>
> >> Tested-by: Priit Laes <plaes@...es.org>
> >> ---
> >
> > You *must* sign off any patches you are sending, please see
> > SubmittingPatches.
> 
> I have sent these patches in the past.

Mike's point was that since it's Priit that he's submitting the
patches, he must add his SoB.

> Besides this non-technical objection there were multiple technical
> objections.
> 
> IIRC one was that the driver does not handle the case when the DMA
> channels are not available. As I understand it the channels are
> exclusively reserved for a particular peripherial on sunxi platform so
> this ShoulNotHappen(tm). So it's probably fine for the driver to fail
> probe  when you have broken DT or no DMA engine support for sunxi
> platform.

There's a quite trivial scenario that would trigger this: if the dma
driver or dmaengine is not enabled / loaded.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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