[alsa-devel] [Audio Driver Low power state]

[Gomathi Kumar]

Hi all,

I am new to kernel work and am trying to understand the low power state of
audio driver.

I am using ALC262 codec, hda_intel and 3.10 kernel code.
In this codec, d3_stop_clk flag is not set. So in the code flow I was able
to understand the following.

if (!codec->pm_down_notified &&
        !bus->power_keep_link_on && (state & AC_PWRST_CLK_STOP_OK))

this particular condition in hda_power_work function fails, as
power_keep_link_on flag is directly based on d3_stop_clk flag.

codec->d3_stop_clk = snd_hda_codec_get_supported_ps(codec, fg,
                                        AC_PWRST_CLKSTOP);

I modified the if condition to not check the power_keep_link_on flag. After
this change the audio is consuming lesser power, but I am not able to see
it going to suspend/runtime suspend.

*Please clarify what is happening when I modify the if condition and how
audio device is consuming low power?*

*Also please help me understand, the significance of flags EPSS and
D3_STOP_CLK and if they can be set by software code. *

Thanks,
Gomathi