On Tue, Nov 14, 2017 at 05:27:42PM +0900, Takashi Sakamoto wrote: > In my understanding, kernel's service of delayed work relies on kernel's > timer service. Resolution of the service is quite coarse in this purpose, at > least for several phases of word select clock. In the worst case when task > scheduling is too delay, many audio samples are not presented by the DAC in > the beginning of playback. I can easily imagine that users get confused. Yes, the delayed work might be delayed a lot more than expected under load (or possibly for other reasons). > In your patch description, 5 word select phases after 'the first command'. > According to "Digital Attenuator" section per page 44 of AK4613 English > datasheet (AsahiKASEI 2015, MS1052-E-05)[1], your 'the first command' seems > to be the previous command issueing of 'power-down release command'. In my > understanding, in ak4613 codec driver, issueing of the previous command is > done in 'ak4613_set_bias_level()'. If there's a guarantee for DAPM stuffs to > call this function on any non-IRQ context, it's better to call the > subsequent commands in the function with interval of sleep functionality > with finer resolution (e.g. usleep_range()) but I don't know exactly that > any components has guarantee to receive word select clock when the function > is called. The problem with set_bias_level() for this might be that the clocks aren't all running until audio is triggered... it's tricky to find a good place to put this that's in line. I'm thinking we might want to add a post trigger callback for cases like this, digital_mute() kind of has that job right now (since it exists mainly to cover up things like controllers that output nonsense during startup) but it'd be a bit of an abuse to just use it as-is. Probably easiest though.
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