[PATCH 5/9] dmaengine: provide a common function for completing a dma descriptor

[Boojin Kim]

Vinod Koul wrote:
> Sent: Monday, April 23, 2012 7:01 PM
> To: Russell King - ARM Linux
> Cc: 'Stephen Warren'; 'Linus Walleij'; 'Srinidhi Kasagar'; Boojin Kim; 'Dan Williams'; 'Li Yang';
> linuxppc-dev at lists.ozlabs.org; linux-arm-kernel at lists.infradead.org
> Subject: Re: [PATCH 5/9] dmaengine: provide a common function for completing a dma descriptor
>
> On Mon, 2012-04-23 at 10:50 +0100, Russell King - ARM Linux wrote:
> > On Mon, Apr 23, 2012 at 06:40:06PM +0900, Boojin Kim wrote:
> > > I met a problem on DMA cyclic mode (DMA_CYCLIC) for sound playback.
> > > Kernel BUG occurs during DMA transfer with DMA cyclic mode.
> > > This patch makes the cookies into zero. But, cookies should be kept
> > > during cyclic mode because cyclic mode re-uses the cookies.
> >
> > The protection is there to prevent cookies being accidentally re-used.
> > If you're running a cyclic transfer, even then you shouldn't be completing
> > the same cookie time and time again - I think Vinod also concurs with this.
> Right :)
> I recently committed patch for imx-dma which doesn't mark the cyclic
> descriptor as complete. Descriptor represents a transaction and makes no
> sense to complete t if the transaction is still continuing.
Dear Vinod,
you already fixed it. :) thanks.
And I have other question. (Actually, It doesn't relate to this patch.)
I met the DMA probing fail problem on Linux 3.4.
It's because the return value on regulator_get() is changed
from ENODEV to EPROBE_DEFER in case not to supply a vcore regulator.
So, I try to change the check value about the return value of regulator_get()
in amba_get_enable_vcore()from ENODEV to EPROBE_DEFER.
How about it ? Do you already fix it too?

Thanks,
Boojin

> >
> > I think our preference is for cyclic transfers to entire remain uncompleted,
> > or to get a new cookie each time they allegedly "complete".
> No it is not complete. Cyclic never completes, it aborts when user
> wants. The "notification" interrupt is for updating the
> counters/notifying (timestamp/periods elapsed in sound), and shouldn't
> be used for anything else
>
> --
> ~Vinod
>
>
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