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Message-ID: <1332746918.19804.84.camel@vkoul-udesk3>
Date: Mon, 26 Mar 2012 12:58:38 +0530
From: Vinod Koul <vinod.koul@...ux.intel.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Ravi Kumar V <kumarrav@...eaurora.org>, tsoni@...eaurora.org,
Russell King <linux@....linux.org.uk>,
linux-arm-msm@...r.kernel.or, linux-kernel@...r.kernel.org,
Bryan Huntsman <bryanh@...eaurora.org>,
Daniel Walker <dwalker@...o99.com>,
Dan Williams <dan.j.williams@...el.com>,
David Brown <davidb@...eaurora.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 2/2] DMAEngine: Add DMAEngine driver based on old
MSM ADM DMA APIs
On Mon, 2012-03-26 at 09:17 +0200, Linus Walleij wrote:
> On Thu, Mar 22, 2012 at 3:23 PM, Ravi Kumar V <kumarrav@...eaurora.org> wrote:
>
> This stuff:
>
> > +enum adm_flush_type {
> > + ADM_FORCED_FLUSH,
> > + ADM_GRACEFUL_FLUSH,
> > +};
>
> > +/*
> > + * Controlling the hardware channel like stopping, flushing.
> > + */
> > +static int msm_dma_chan_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> > + unsigned long arg)
> > +{
> > + enum adm_flush_type cmd_type = arg;
> > +
> > + if (cmd == DMA_TERMINATE_ALL) {
> > + switch (cmd_type) {
> > + case ADM_GRACEFUL_FLUSH:
> > + msm_dmov_stop_cmd(chan->chan_id, NULL, 1);
> > + break;
> > + case ADM_FORCED_FLUSH:
> > + /*
> > + * We treate default as forced flush
> > + * so we fall through
> > + */
> > + default:
> > + msm_dmov_stop_cmd(chan->chan_id, NULL, 0);
> > + break;
> > + }
> > + }
> > + return 0;
> > +}
>
> This is an interesting way of using the opaque arg. Can you describe
> the different semantics of graceful vs forced flush so we understand
> the usecases for them?
>
> DMA_TERMINATE_ALL is usually not very graceful.
>
> DMA_PAUSE might be the semantic you're looking for as the
> graceful path, and then you can do away with this strange
> enum altogether.
I am not a big fan of opaque objects. Btw client should use
dmaengine_terminate_all() only
--
~Vinod
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