On Thu, Oct 18, 2012 at 11:55:40PM +0100, Russell King - ARM Linux wrote: > On Thu, Oct 18, 2012 at 03:20:46PM -0700, Mark A. Greer wrote: > > This patch seems fairly stable but I've only tested omap-sham (crypto) > > and omap_hsmmc (mmc) on an am37x EVM. I also enabled burst mode but > > that made the system unstable when exercising either omap-sham or > > omap_hsmmc. I'm unaware of any errata that would make this an unwanted > > modification but I haven't checked all of the SoCs. Are there other > > reasons that this should be applied?? > > It definitely needs checking with audio, because it will affect the > pointer position in relation to audio output, and it will have an > effect on how much audio data is lost over a pause/resume event. > > Unfortunately, the OMAP DMA hardware has no way to do a proper "pause", > it can only do a "stop" which involves dumping its FIFOs on the floor > in the case of anything but a DEV->MEM transfer. So the more data > held in the DMA hardware, the more is lost on pause. Hmm, interesting. Is there a way to tweak DMA params like this on a per logical channel basis using the dmaengine API? I don't see any but I could have missed it. If not, are you open to adding such a thing (e.g., extend 'enum dma_ctrl_flags' with DMA_ENABL_PREFETCH)? Mark -- -- 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
