[PATCH v2 4/4] ARM: dts: amlogic: meson8-fernsehfee3: Describe regulators

[Martin Blumenstingl]

On Mon, Apr 28, 2025 at 12:44 PM J. Neuschäfer via B4 Relay
<devnull+j.ne.posteo.net at kernel.org> wrote:
>
> From: "J. Neuschäfer" <j.ne at posteo.net>
>
> The fernsehfee3 board uses a Ricoh RN5T618 PMIC to generate various
> voltages. Board schematics are not available, but the regulator voltages
> found in /sys/kernel/debug/regulator/regulator_summary match those in
> meson8m2-mxiii-plus.dts:
>
>  DCDC1               0    0      0 unknown  1100mV     0mA     0mV     0mV
>  DCDC2               0    0      0 unknown  1150mV     0mA     0mV     0mV
>  DCDC3               0    0      0 unknown  1500mV     0mA     0mV     0mV
>  LDO1                0    0      0 unknown  2900mV     0mA     0mV     0mV
>  LDO2                0    0      0 unknown  1800mV     0mA     0mV     0mV
>  LDO3                0    0      0 unknown  1800mV     0mA     0mV     0mV
>  LDO4                0    0      0 unknown  2850mV     0mA     0mV     0mV
>  LDO5                0    0      0 unknown  1800mV     0mA     0mV     0mV
>  LDORTC1             0    0      0 unknown  2700mV     0mA     0mV     0mV
>  LDORTC2             0    0      0 unknown   900mV     0mA     0mV     0mV
>
> This patch takes the following approach:
>
>  - Copy RN5T618 regulator nodes from meson8m2-mxiii-plus.dts
>  - Remove some of the regulator names, which do not seem to apply
>  - Verify regulator supply relations by starting without any relations
>    (and without regulator-always-on) and seeing what breaks when the
>    kernel turns off "unused" regulators.
>
> This results in the following observations:
>
>  - When LDO1 is turned off, the board resets
>  - When DCDC1, DCDC2, DCDC3, LDO2, or LDO5 are turned off, the board (as
>    observed through the serial port) stops running, so these must stay on
>    at all times.
>  - LDO4 (VCC2V8) appears to be unused on this board.
>  - LDO3 (VCC1V8_USB) must stay on in order for USB to work, both the
>    external USB ports and the internal USB wifi module.
>
> The cpu-supply and mali-supply relations are also copied from
> meson8m2-mxiii-plus.dts
>
> Signed-off-by: J. Neuschäfer <j.ne at posteo.net>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>

Thanks for the detailed summary!