linux-kernel - Re: [PATCH] dmaengine: qcom_bam

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Date:	Thu, 17 Jul 2014 13:31:10 -0500
From:	Andy Gross <agross@...eaurora.org>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] dmaengine: qcom_bam_dma: Add descriptor flags

On Mon, Jul 14, 2014 at 10:06:16PM +0530, Vinod Koul wrote:
> On Fri, May 30, 2014 at 03:49:50PM -0500, Andy Gross wrote:
> > This patch adds support for end of transaction (EOT) and notify when done (NWD)
> > hardware descriptor flags.
> > 
> > The EOT flag requests that the peripheral assert an end of transaction interrupt
> > when that descriptor is complete.  It also results in special signaling protocol
> > that is used between the attached peripheral and the core using the DMA
> > controller.  Clients will specify DMA_PREP_INTERRUPT to enable this flag.
> > 
> > The NWD flag requests that the peripheral wait until the data has been fully
> > processed by the peripheral before moving on to the next descriptor.  Clients
> > will specify DMA_PREP_FENCE to enable this flag.
> 
> I am going to apply this, but pls send a follow up patch to add comments on the
> flags and their behaviour. I think it is required!

Will do.

<snip>

> >  #define DESC_FLAG_EOT BIT(14)
> >  #define DESC_FLAG_EOB BIT(13)
> > +#define DESC_FLAG_NWD BIT(12)
> explaining behvaiour will help..

In the followup, I'll put in a lengthy description of the INT/EOT/NWD and how
they are used in the signaling to/from the attached peripheral.


Thanks!

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