On Fri, 1 Oct 2010 09:39:06 +0300 Peter Ujfalusi <[email protected]> wrote:
> Implement the suggested workaround for OMAP3 regarding to sDMA draining > issue, when the channel is disabled on the fly. > This errata affects the following configuration: > sDMA transfer is source synchronized > Buffering is enabled > SmartStandby is selected. > > The issue can be easily reproduced by creating overrun situation while > recording audio. > Either introduce load to the CPU: > nice -19 arecord -D hw:0 -M -B 10000 -F 5000 -f dat > /dev/null & \ > dd if=/dev/urandom of=/dev/null > > or suspending the arecord, and resuming it: > arecord -D hw:0 -M -B 10000 -F 5000 -f dat > /dev/null > CTRL+Z; fg; CTRL+Z; fg; ... > > In case of overrun audio stops DMA, and restarts it (without reseting > the sDMA channel). When we hit this errata in stop case (sDMA drain did > not complete), at the coming start the sDMA will not going to be > operational (it is still draining). > This leads to DMA stall condition. > On OMAP3 we can recover with sDMA channel reset, it has been observed > that by introducing unrelated sDMA activity might also help (reading > from MMC for example). > > The same errata exists for OMAP2, where the suggestion is to disable the > buffering to avoid this type of error. > On OMAP3 the suggestion is to set sDMA to NoStandby before disabling > the channel, and wait for the drain to finish, than configure sDMA to > SmartStandby again. > > Signed-off-by: Peter Ujfalusi <[email protected]> > --- Acked-by: Jarkko Nikula <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
