On Thu 31 Jan 02:44 PST 2019, Srinivas Kandagatla wrote: > > > On 31/01/2019 01:16, Bjorn Andersson wrote: > > On Thu 15 Nov 10:49 PST 2018, Srinivas Kandagatla wrote: > > > > > APR communication with DSP is not atomic in nature. > > > Its request-response type. Trying to pretend that these are atomic > > > and invoking apr client callbacks directly under atomic/irq context has > > > endless issues with soundcard. It makes more sense to convert these > > > to nonatomic calls. This also coverts all the dais to be nonatomic. > > > > > Hi Srinivas, > > > > Sorry for not looking at this before. > > > NP, thanks for the review! > > > Are you sure that you're meeting the latency requirements of low-latency > > audio with this change? > > Low and Ultra Low Latency audio is not supported in the exiting upstream > qdsp drivers. > Sure, but we want the design to allow for that still, either in future upstream or by additional downstream code. > Also it depends on definition of "latency", is the latency referring to > "filling the data" or "latency between DSP command and response". > I'm referring to the latency between the message from the DSP until we give it a new buffer. > For former case as long as we have more samples in our ring buffer there > should be no latency in filling the data. > For later case it should not really matter as long as former case is taken > care off. > > Low latency audio involves smaller sample sizes and no or minimal > preprocessing in DSP so am guessing that we should be okay with responses in > workqueue as long as we have good size ring buffer. > Relying on more buffered data will increase the latency of the audio, preventing you from doing really low-latency things. Regards, Bjorn
