linux-kernel - Re: [PATCH 10/18] spi: s3c64xx: Do not require legacy DMA API in case of S3C64XX

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Message-ID: <20130813202941.GH6427@sirena.org.uk>
Date:	Tue, 13 Aug 2013 21:29:41 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	Dan Williams <djbw@...com>, Jaroslav Kysela <perex@...ex.cz>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mike Turquette <mturquette@...aro.org>,
	Padmavathi Venna <padma.v@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Sangbeom Kim <sbkim73@...sung.com>,
	Takashi Iwai <tiwai@...e.de>, Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH 10/18] spi: s3c64xx: Do not require legacy DMA API in
 case of S3C64XX

On Tue, Aug 13, 2013 at 10:20:19PM +0200, Tomasz Figa wrote:
> On Tuesday 13 of August 2013 21:18:16 Mark Brown wrote:

> > 	if (dev->chancnt > 1 && !dma_has_cap(DMA_PRIVATE, dev->cap_mask))
> > 		list_for_each_entry(chan, &dev->channels, device_node) {
> > 			/* some channels are already publicly allocated */
> > 			if (chan->client_count) {

> > which is happening because dma1chan0 (which is on the same DMA
> > controller as the SPI controller) and in fact every other DMA channel
> > had references grabbed by the network stack dmaengine helpers which I'd
> > enabled in config.  The fact that they do that is unhelpful, it renders
> > the API mostly useless, but is nothing to do with this series.

> I believe you just found another brokenness of current DMA channel 
> matching.

Yeah, at first glance the reference grabbing thing seems a bit peculiar.
I didn't research why it's done that way yet.

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