[alsa-devel] [RFC] disabling ALSA period interrupts
bossart.nospam at gmail.com
Wed May 12 15:50:42 CEST 2010
> It seems the requirement is just to have as least wakeups as possible
> in order to
> maximize power savings.
> If so, then how about setting the period size slightly smaller than
> the ring-buffer: the
> difference being just enough to refill the ring buffer. Of course, you
> would have to
> enforce full-buffer-size as the start threshold.
> We do just that to implement low-power-audio-mode for latest Samsung
> SoC's I2S blocks.
Thanks for the heads-up Jassi, this is interesting info that does show
the need to reduce the number of wakeups in embedded low-power
This might be almost equivalent to the timer approach in terms of # of
wakeups, however the timer can be reprogrammed on-the-fly whereas
periods can only be changed by closing and reopening the device. You
can also adjust the timer shall underflows occur. And the timer slack
lets the kernel group events. Not to mention that you will need
specific apps written to make use of this mode. The only drawback of
the timer approach is that you need to keep track of drifts between
system and audio clock and that you need the hardware and driver to
report the hw_ptr with precision.
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