linux-kernel - Re: [PATCH] dma: omap-dma: add support for pause of non-cyclic transfers

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Date:	Fri, 7 Aug 2015 17:35:53 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	nsekhar@...com, linux-omap@...r.kernel.org,
	linux-serial@...r.kernel.org, john.ogness@...utronix.de,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] dma: omap-dma: add support for pause of non-cyclic
 transfers

On Fri, Aug 07, 2015 at 06:20:44PM +0200, Sebastian Andrzej Siewior wrote:
> On 08/07/2015 06:07 PM, Peter Hurley wrote:
> >> If we look at what 8250-dma.c is doing:
> >>
> >>                 if (dma->rx_running) {
> >>                         dmaengine_pause(dma->rxchan);
> >>
> >> It's 8250-dma.c which is silently _ignoring_ the return code, failing
> >> to check that the operation it requested worked.  Maybe this should be
> >> WARN_ON(dmaengine_pause(dma->rxchan)) or at least it should print a
> >> message?
> > 
> > Thanks for the suggestion; I'll hold on to that and push it after we add
> > the 8250 omap dma pause in mainline.
> 
> I have a patch ready with WARN_ON_ONCE() for 8250-omap and 8250-dma.
> This warning would trigger on am335x/edma until v4.2-rc1 and omap-dma
> based version is open. I could post it if you want me to.
> Besides that those two, there are four other drivers ignoring the
> return code dmaengine_pause().

It'll probably be a good idea if those are fixed too, and also have a
__must_check annotation on the declaration of dmaengine_pause() to
prevent future mishaps like this.

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