Peter Ujfalusi 0e4905c019 OMAP3: DMA: Errata i541: sDMA FIFO draining does not finish ... 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 <peter.ujfalusi@nokia.com> Acked-by: Jarkko Nikula <jhnikula@gmail.com> Acked-by : Santosh Shilimkar <santosh.shilimkar@ti.com> Acked-by : Manjunath Kondaiah G <manjugk@ti.com> Signed-off-by: Tony Lindgren <tony@atomide.com>		2010-10-11 14:18:56 -07:00
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plat	OMAP3: DMA: Errata i541: sDMA FIFO draining does not finish	2010-10-11 14:18:56 -07:00