Hi Pierre-Louis, Bard,
I've been looking into getting some Cherry Trail + RT5645 devices with a mono speaker I have to work properly.
Specifically the goal is to mix the right channel into the left output, so that sounds which are only played over the right channel do not get lost.
I'm using this UCM file: https://github.com/plbossart/UCM/blob/master/byt-rt5640/HiFi
Looking at the rtl5640 UCM file, getting the mono speaker to work (in a first simple attempt) should be as simple as replacing:
cset "name='SPOR MIX SPKVOL R Switch' on"
With
cset "name='SPOL MIX SPKVOL R Switch' on"
But this does not work, the speaker test sound for the right speaker is still silent (works with headphones).
I've also looked into directly poking the RT5645_SPO_MIXER i2c register for testing, but when checking its value with the original unmodified UCM file:
[root@localhost ~]# i2cget -y -f 1 0x1a 0x48 w 0x06c8
That is: 0xc806 as the output of i2cget "w" mode needs byteswapping. Note that both the RT5645_M_SV_L_SPM_L and RT5645_M_SV_R_SPM_L bits are already cleared, which is weird as this is before I've modified anything. Also the RT5645_M_SV_R_SPM_R bit is cleared, but that is expected.
Even if I manually set reg 0x48 to 0x07c8 which AFAIK should enable output of both left and right channels on the left speaker I still only get sounds played on the left channel.
Any insights / help with this would be very much welcome.
Regards,
Hans