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Fex

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  1. Like
    Fex got a reaction from JRoe in Power line hum on Lime2 with mainline kernel   
    I found a workaround!
     
    After looking at some kernel stack traces, I found that this guy was responsible: https://www.kernel.org/doc/html/latest/sound/soc/dapm.html
     
    When the PCM device is closed the following happens in the kernel:
    snd_pcm_release() -> soc_pcm_close() -> delay of `pmdown_time` -> close_delayed_work() The last function powers down the audio subsystem, causing the hum. To circumvent this behavior, I simply set `pmdown_time` to -1:
    echo -1 > /sys/devices/platform/soc@01c00000/1c22c00.codec/cdc/pmdown_time Now, once the sound subsystem is powered on, it stays powered on. Not ideal but it seems to work.
  2. Like
    Fex got a reaction from Bernie_O in Power line hum on Lime2 with mainline kernel   
    I found a workaround!
     
    After looking at some kernel stack traces, I found that this guy was responsible: https://www.kernel.org/doc/html/latest/sound/soc/dapm.html
     
    When the PCM device is closed the following happens in the kernel:
    snd_pcm_release() -> soc_pcm_close() -> delay of `pmdown_time` -> close_delayed_work() The last function powers down the audio subsystem, causing the hum. To circumvent this behavior, I simply set `pmdown_time` to -1:
    echo -1 > /sys/devices/platform/soc@01c00000/1c22c00.codec/cdc/pmdown_time Now, once the sound subsystem is powered on, it stays powered on. Not ideal but it seems to work.
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