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

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Date:	Fri, 07 Aug 2015 18:20:44 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Peter Hurley <peter@...leysoftware.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	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 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().

Sebastian
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