Le 22/05/24 - 07:52, Takashi Iwai a écrit : > On Tue, 21 May 2024 20:32:59 +0200, > Mark Brown wrote: > > > > On Tue, May 21, 2024 at 10:31:12AM +0200, Louis Chauvet wrote: > > > > > To address this DMA issue, I have created a patch [1] that guarantees the > > > completion of the DMA transfer upon the return of xdma_synchronize. This > > > means xdma_synchronize now sleeps, but looking at other drivers around it > > > appears expected to be able to do so. > > > > You need to set the nonatomic flag for the PCM to allow this, the > > default is that triggers run in atomic context. > > Right, that's a most straightforward solution. It implies that the > period updates must be in non-atomic, i.e. use a threaded irq handler > in most cases. > > If the synchronization is needed for assuring the hardware stop, there > is an alternative with PCM sync_stop callback, too. The callback is > called at each time after a stream gets stopped before the next action > (that is, either prepare, hw_params or close). It's only for > stopping, and there is no similar way for sync of a stream start, > though. > > > thanks, > > Takashi > Hi! Thank you for your prompt responses! I have currently implemented the solution with sync_stop, as it is precisely what I need to do, and it works perfectly. As I may need to backport this driver up to 4.19, sync_stop was not yet available, so I will look into the threaded IRQ solution, which sounds promising. Thank you both very much! Best regards, Louis Chauvet -- Louis Chauvet, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
