> -----Original Message----- > From: Valkeinen, Tomi > Sent: Thursday, January 09, 2014 1:52 PM > To: Hiremath, Vaibhav; Ivaylo Dimitrov > Cc: Tony Lindgren; linux-omap@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-fbdev@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2] ARM: omapfb: add coherent dma memory support > > On 2014-01-09 07:06, Hiremath, Vaibhav wrote: > > > I am seeing underflow issue on AM43x device if I use omapfb_vram argument. > > Did you see this on OMAP? > > > > I am using "omapfb_vram=10M@0xA0000000", and I believe it is correct way > of usage. > > Hmm ok... The AM4x seems to have issues anyway, as we're seeing underflows > easily in other situations also. > > Well, there's a small difference in the allocation. The normal dma alloc uses > dma_alloc_attrs() and passes DMA_ATTR_WRITE_COMBINE as a flag, whereas > allocating from the absolute address just uses the piece of memory. I couldn't > find how to set write-combine for the abs memory area. > > Then again, that's for CPU caching, so I don't see why it would affect DSS as > such (but that's still something we should measure, cpu read/write perf for > normal and abs allocation). > > The only thought I have is that somehow the reserved memory area is missing > some configuration that is done for the rest of the memory. But that's purely a > guess, this is totally out of my area of expertise... > > Vaibhav, just to be sure, can you run both with normal dma_alloc and with the > reserve, and verify that the dispc register dumps are the same? > I don't see how they could be different, but just to be sure. > Will check and update you shortly. Thanks, Vaibhav -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
