21.05.2019 7:55, Vinod Koul пишет: > On 08-05-19, 10:24, Jon Hunter wrote: >> >> On 05/05/2019 19:12, Dmitry Osipenko wrote: >>> The DMA_PREP_INTERRUPT flag means that descriptor's callback should be >>> invoked upon transfer completion and that's it. For some reason driver >>> completely disables the hardware interrupt handling, leaving channel in >>> unusable state if transfer is issued with the flag being unset. Note >>> that there are no occurrences in the relevant drivers that do not set >>> the flag, hence this patch doesn't fix any actual bug and merely fixes >>> potential problem. >>> >>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >> >> >From having a look at this, I am guessing that we have never really >> tested the case where DMA_PREP_INTERRUPT flag is not set because as you >> mentioned it does not look like this will work at all! > > That is a fair argument >> >> Is there are use-case you are looking at where you don't set the >> DMA_PREP_INTERRUPT flag? >> >> If not I am wondering if we should even bother supporting this and warn >> if it is not set. AFAICT it does not appear to be mandatory, but maybe >> Vinod can comment more on this. > > This is supposed to be used in the cases where you submit a bunch of > descriptors and selectively dont want an interrupt in few cases... > > Is this such a case? The flag is set by device drivers. AFAIK, none of the drivers that are used on Tegra SoC's make a use of that flag, at least not in upstream.
