linux-kernel - Re: [PATCH] dma: shdma: transfer based runtime PM

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Date:	Tue, 30 Aug 2011 15:27:37 +0530
From:	Vinod Koul <vinod.koul@...ux.intel.com>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
	Dan Williams <dan.j.williams@...el.com>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH] dma: shdma: transfer based runtime PM

On Tue, 2011-08-30 at 09:12 +0200, Guennadi Liakhovetski wrote:
> On Mon, 29 Aug 2011, Vinod Koul wrote:
> > > > Something like:
> > > > /* since callback is set for last descriptor of chain, we call runtime
> > > >  * put for that desc alone
> > > >  */
> > > > list_for_each_entry_safe(desc, __desc, sh_chan->ld_queue, node) {
> > > > 	if (desc->async_tx.callback)
> > > > 		pm_runtime_put(device);
> > > 
> > > Not all dma users have callbacks.
> > Do you have such usage today, at least I dont :)
> > Nevertheless, in tx_submit adding a simple flag in your drivers
> > descriptor structure can tell you whether to call _put() or not. Agreed?
> 
> Yes, I agree, that one could make this work too. Still, I do not 
> understand how and why this is better to the extent, that I have to 
> reimplement my patch, retest and resubmit it. Maybe Dan or Paul have an 
> opinion on this?
But wont it make code look simpler and cleaner, you don't reply on your
counters but on pm_runtime infrastructure to do the job. You juts need
to call _put/_get at right places, which IMO l;ooks lot simpler than
current approach

-- 
~Vinod

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