From mboxrd@z Thu Jan 1 00:00:00 1970 From: jhnikula@gmail.com (Jarkko Nikula) Date: Mon, 4 Oct 2010 12:50:19 +0300 Subject: [PATCH v4 1/4] omap: dma: Fix buffering disable bit setting for omap24xx In-Reply-To: References: <1286180294-32618-1-git-send-email-peter.ujfalusi@nokia.com> <1286180294-32618-2-git-send-email-peter.ujfalusi@nokia.com> Message-ID: <20101004125019.98228ee3.jhnikula@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, 4 Oct 2010 14:44:28 +0530 "G, Manjunath Kondaiah" wrote: > > > > -----Original Message----- > > From: linux-omap-owner at vger.kernel.org > > [mailto:linux-omap-owner at vger.kernel.org] On Behalf Of Peter Ujfalusi > > Sent: Monday, October 04, 2010 1:48 PM > > To: Tony Lindgren > > Cc: linux-omap at vger.kernel.org; Jarkko Nikula; > > linux-arm-kernel at lists.infradead.org > > Subject: [PATCH v4 1/4] omap: dma: Fix buffering disable bit > > setting for omap24xx > > > > From: ext Jarkko Nikula > > > > 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