On Friday 08 May 2009 09:40:44 ext Jarkko Nikula wrote: > It really does fix the power-up & -down pops on Beagle. By listening > carefully I can hear slight power-up and -down pops but only if really > focusing on it. > > But now the audio output is distorted and volume level is a little bit > lower. Without the patch it plays fine. Is it possible that now the > output voltage is not correctly biased? Worth to check with a scope. Well, that's what you get, when you are testing audio with /dev/zero and /dev/urandom... I have not noticed that the random noise got more random ;) What you have described is correct, it is heavily distorted. But I have debugged this further and I believe I know what is going on: The sequence for disable according to the documentation: HS_POP_SET:RAMP_EN = 0 HS_POP_GAIN:HSL_GAIN, HSR_GAIN = 0 HS_POP_SET:VMID_EN = 0 Now what is missing from this is that after setting the HS_POP_SET:RAMP_EN = 0 it will take RAMP_DELAY time for the VMID to reach 0. Since we are not waiting between RAMP_EN = 0 and VMID_EN = 0, the VMID has been cut, which causes the 'tuck' on the headset output. In case of the Beagle board the ramp delay can be configured(MCLK=26MHz): 20ms - 2581ms, by default it is 20ms. To verify this I have added mdelay(30) after the RAMP_EN = 0, and there were no 'tuck'. However when I increased the RAMP_DELAY (to 40ms, or longer) the 'tuck' reappeared. How to solve this? Realistically we can not add 2581ms delay to the headsetl_event function... We could keep the VMID enabled all the time (which increases the idle power consumption by ~0.001A), but then the muting of the headset (HS_POP_GAIN:HSL_GAIN, HSR_GAIN = 0) will give the 'tuck'... In power consumption the difference between HS_POP_GAIN:HSL_GAIN, HSR_GAIN == 0 and HS_POP_GAIN:HSL_GAIN, HSR_GAIN != 0 is about ~0.01A, which is significant in my opinion. Using a timer to finish the ramp down? Anyways, this seams quite bad. I will think about it over the weekend... Any ideas? -- Péter _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
