On 8/2/2018 3:26 PM, Mark Brown wrote: > On Thu, Aug 02, 2018 at 12:11:54PM +0530, Akshu Agrawal wrote: >> In capture case we don't want ACP to SYSMEM dma >> to be circular. This is because if an in place DSP >> filter is applied to captured output then circular DMA >> can overwrite the filter value with stale data. > > Isn't that just a problem with userspace not giving itself enough buffer > to get the in place processing done before we loop round again. This > will simply change the type of error, it won't actually fix anything > AFAICT but perhaps I'm missing something. > Sorry for the delayed reply. Will try and explain more on whats happening: We have 2 DMAs, one being I2S->ACP(Audio Co-Processor memory) and the second being ACP->SYSMEM. When ACP->SYSMEM is circular then this DMA is faster and keeps updating from ACP memory. This leaves no time for user space to do any kind of in place post processing. This design works fine if the user reads the data from SYSMEM at capture rate (that is the rate at which I2S->ACP transfer happens). But, when an in place post processing happens on SYSMEM then the data gets overwritten. Sending and updated series with changes in 2/3 and 3/3 patch. Thanks, Akshu _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
