"Premi, Sanjeev" <pr...@ti.com> writes: >> -----Original Message----- >> From: davinci-linux-open-source-boun...@linux.davincidsp.com >> [mailto:davinci-linux-open-source-boun...@linux.davincidsp.com >> ] On Behalf Of Kevin Hilman >> Sent: Wednesday, January 06, 2010 5:09 AM >> To: Subrahmanya, Chaithrika >> Cc: davinci-linux-open-source@linux.davincidsp.com >> Subject: Re: Audio quality with CPU frequency scaling >> >> "Chaithrika U S" <chaithr...@ti.com> writes: >> >> > Kevin, >> > >> > With the cpufreq support on DA850/OMAP-L138 SoC we are observing >> > that audio does not function as expected at all sampling rates >> > for various operating points. At a CPU frequency of 96MHz, audio >> > works fine with a sampling frequency of 8kHz. For other sampling >> > rates, there are lot of underrun/overrun errors. This is because >> > of EDMA also runs at a lower speed and is not able to transfer >> > data at the desired rate. >> > >> > To overcome the above, we can depend on the user to set the scaling >> > min frequency to be the same as scaling max frequency (in this case >> > 300 MHz) before starting aplay/arecord or temporarily move to >> > performance governor so that the audio quality is not affected. >> > >> > Do you think this is the right approach to this problem? Any other >> > solutions you suggest exploring? >> >> An alternative to relying on the user to change the CPUfreq policy is >> to have the audio driver itself do that. Based on the sample rate and >> clock frequency, the audio driver should be able to determine that the >> EDMA rate will not be fast enough and set a CPUfreq policy so that >> lower frequencies are not attempted. When the audio driver is done, >> it can set the policy back. > > Kevin, > > Wouldn't this mean that driver is directly influencing the policy? >
Yes indeed, but if it is a question of correct functionality, I don't have a problem with that. If a driver is changing policy for power vs. performance tradeoff, I have a problem with that. Kevin _______________________________________________ Davinci-linux-open-source mailing list Davinci-linux-open-source@linux.davincidsp.com http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
