[alsa-devel] [PATCH 0/2] RFC: support for audio wall clock

[Pierre-Louis Bossart]

On 6/29/2012 8:03 PM, Raymond Yau wrote:
> Do suspsend/resume affect the usage of the wall clock ? Those au88x0 
> also have a 32 bit register which return the ticks from a 12.288 Mz 
> oscillator (i.e. 256 x 48000Hz) , this register wrap around in around 
> 349.5 seconds Can this clock be used to determine the drift too ? 

In theory any clock can be used, as long as it's synchronous with the 
bitclock used in the serial stream. I am planning to use our 19.2 MHz 
clock on non HDAudio platforms, a 12.288 would work at well. The cycle 
count will be translated to ns, the initial clock base has a marginal 
impact on the result.
I haven't validated anything related to suspend/resume. It should work 
if the trigger is invoked on resume where the audio wallclock is 
reinitialized with the system time
-Pierre