Re: [PATCH v4 1/4] omap: dma: Fix buffering disable bit setting for omap24xx

[Jarkko Nikula <jhnikula@gmail.com>]

On Mon, 4 Oct 2010 14:44:28 +0530
"G, Manjunath Kondaiah" <manjugk@ti.com> wrote:

> 
> 
> > -----Original Message-----
> > From: linux-omap-owner@vger.kernel.org 
> > [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Peter Ujfalusi
> > Sent: Monday, October 04, 2010 1:48 PM
> > To: Tony Lindgren
> > Cc: linux-omap@vger.kernel.org; Jarkko Nikula; 
> > linux-arm-kernel@lists.infradead.org
> > Subject: [PATCH v4 1/4] omap: dma: Fix buffering disable bit 
> > setting for omap24xx
> > 
> > From: ext Jarkko Nikula <jhnikula@gmail.com>
> > 
> > An errata workaround for omap24xx is not setting the 
> > buffering disable bit
> > 25 what is the purpose but channel enable bit 7 instead.
> 
> ...
> 
> > diff --git a/arch/arm/plat-omap/dma.c 
> > b/arch/arm/plat-omap/dma.c index ec7eddf..6914ccf 100644
> > --- a/arch/arm/plat-omap/dma.c
> > +++ b/arch/arm/plat-omap/dma.c
> > @@ -999,8 +999,9 @@ void omap_start_dma(int lch)
> >  	 * Errata: On ES2.0 BUFFERING disable must be set.
> >  	 * This will always fail on ES1.0
> >  	 */
> 
> Sorry, I didn't catch this with earlier patch.
> 
> Looks like wrong comment. only on 2430ES1.0 and for all omap2420, 
> buffer disable should be set. 
> I feel below description will be useful to the reader:
> "Errata: Inter Frame DMA buffering issue(All OMAP2420 and OMAP2430ES1.0):
> DMA will wrongly buffer elements if packing and bursting is enabled.
> This might result in data gets stalled in FIFO at the end of the block.
> Workaround: DMA channels must have BUFFERING_DISABLED bit set to guarantee
> no data will stay in the DMA FIFO in case inter frame buffering occurs.
> 
Ok, no problem. I'll add this to the next version. This is good to get
documented.


-- 
Jarkko