[alsa-devel] iMX6UL EVK with kernel 4.6

[Fabio Estevam]

On Sun, May 1, 2016 at 3:59 PM, Petr Kulhavy <brain at jikos.cz> wrote:

> I have not tried setting the bit 20 of the GPR1 register. How would that be
> set?

If you have memtool installed in your rootfs:

./memtool -32 20E4004=0F560005

You can do this via bootloader prompt or via devmem2 in the Linux prompt.

Without this MCLK will not be out.

>
> Both the 3.x and 4.1 work for me. However you need to set the headphone
> volume to non-zero and especially the pcm output mixer (unmute),
> otherwise the audio path is not routed through and the codec is switched off
> due to power saving (and generates no bclk and lrclk).
> This confused me as well, but after setting the mixer playback stasrts
> working with the Freescale kernel.

I was putting the volume to a suitable value, but didn't touch PCM output mixer.

I see in alsamixer: "PCM Playback -6dB [Off]", but it does not allow
me to change this setting though.