[PATCH v2 0/4] ARM: dts: r8a7790: lager: use demuxer for I2C

[Wolfram Sang]

>    # ./exercise-i2c-demux.sh
>    I2C Demux: i2c-8
>      Master: 1:/i2c at e650800
>    [   97.694487] i2c-rcar e6508000.i2c: probed 0 (1)
>      Master: 0:/i2c at e650000
>    [  102.706365] i2c-demux-pinctrl i2c-8: failed to setup demux-adapter 0 (-19) 0 (0)

Confirmed :( Got today only this far that the ENODEV comes from the PFC
driver. CONFIG_DEBUG_PINCTRL is a good idea for further debugging
probably.

>    3.1 Unfortunately it fails for the I2C2 dmux if the GPIO fallback is
>        present.

Hopefully the same issue.

>    3.2 The test also fails for the I2C3 demux but that appears to be due
>        to a shortcoming in the voltage regulator code which does not
>        appear to like being reinitialised. The kernel complains as follows:

Yes, the demuxer trigger re-bind cycles which are not well considered
and/or tested. E.g. for soc-camera, this patch needed to go upstream:

https://patchwork.linuxtv.org/patch/32473/

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