linux-kernel - Re: [PATCH] dmaengine: bcm2835: Fix polling for completion of DMA with interrupts masked.

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Message-ID: <20160607072121.GM16910@localhost>
Date:	Tue, 7 Jun 2016 12:51:21 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Eric Anholt <eric@...olt.net>
Cc:	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>, dmaengine@...r.kernel.org
Subject: Re: [PATCH] dmaengine: bcm2835: Fix polling for completion of DMA
 with interrupts masked.

On Mon, Jun 06, 2016 at 11:10:38PM -0700, Eric Anholt wrote:
> >> >> -	if (ret == DMA_COMPLETE || !txstate)
> >> >> +	if (ret == DMA_COMPLETE)
> >> >
> >> > Why do you change this? txstate can be NULL, so no point calculating reside
> >> > for those cases
> >> 
> >> The point was to go into the "Calculate where we're at in our current
> >> DMA (if the current DMA is the one we're asking about status for)" path,
> >> so that we could note when the DMA is complete even when there's no
> >> txstate passed in.
> >
> > Can you explain what you mean by current DMA!
> >
> > The claulation is always done for 'descriptor' represnted by the cookie. So
> > it doesnt not matter...!
> 
> By current I mean the current descriptor that has been submitted to the
> hardware, in bcm2835_chan->desc.

As I said, you calculate for the descriptor respresnted by cookie and
not the one getting processed!

-- 
~Vinod

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