Re: [PATCH 3/4] arm64: dts: rockchip: add analog audio to ROCK 4D

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

On 6/30/25 1:19 PM, Nicolas Frattaroli wrote:
> The RADXA ROCK 4D, like many other Rockchip-based boards, uses an ES8388
> analog audio codec. On the production version of the board, the codec's
> LOUT1 and ROUT1 pins are tied to the headphone jack, whereas pins LOUT2
> and ROUT2 lead to a non-populated speaker amplifier that itself leads to
> a non-populated speaker jack. The schematic is still haunted by the
> ghosts of those symbols, but it clearly marks them as "NC".
> 
> The 3.5mm TRRS jack has its microphone ring (and ground ring) wired to
> the codec's LINPUT1 and RINPUT1 pins for differential signalling.
> 
> Furthermore, it uses the SoCs ADC to detect whether the inserted cable
> is of headphones (i.e., no microphone), or a headset (i.e., with
> microphone). The way this is done is that the ADC input taps the output
> of a 100K/100K resistor divider that divides the microphone ring pin
> that's pulled up to 3.3V.
> 
> There is no ADC level difference between a completely empty jack and one
> with a set of headphones (i.e., ones that don't have a microphone)
> connected. Consequently headphone insertion detection isn't something
> that can be done.
> 
> Add the necessary codec and audio card nodes. The non-populated parts,
> i.e. LOUT2 and ROUT2, are not modeled at all, as they are not present on
> the hardware.
> 
> Also, add an adc-keys node for the headset detection, which uses an
> input type of EV_SW with the SW_MICROPHONE_INSERT keycode. Below the
> 220mV pressed voltage level of our SW_MICROPHONE_INSERT switch, we also
> define a button that emits a KEY_RESERVED code, which is there to model
> this part of the voltage range as not just being extra legroom for the
> button above it, but actually a state that is encountered in the real
> world, and should be recognised as a valid state for the ADC range to be
> in so that no "closer" ADC button is chosen.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Enabled CONFIG_SND_SOC_ES8328_I2C and confirm playback works fine:

    $ speaker-test -D hw:ES8388,0 -F S16_LE -c 2 -t wav

Unfortunately the recording doesn't seem to be functional:

    $ arecord -D hw:ES8388,0 -f S16_LE -c 2 -r 48000 -d 5 -V stereo /tmp/test.wav
    Recording WAVE '/tmp/test.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
                                    +00%|00%+

    $ aplay -D hw:ES8388,0 /tmp/test.wav

However, the headset plug detection works correctly:

    $ evtest
    No device specified, trying to scan all of /dev/input/event*
    Available devices:
    /dev/input/event0:	Logitech USB Receiver
    /dev/input/event1:	Logitech USB Receiver Mouse
    /dev/input/event2:	Logitech USB Receiver Consumer Control
    /dev/input/event3:	Logitech USB Receiver System Control
    /dev/input/event4:	adc-keys
    Select the device event number [0-4]: 4
    Input driver version is 1.0.1
    Input device ID: bus 0x19 vendor 0x1 product 0x1 version 0x100
    Input device name: "adc-keys"
    Supported events:
      Event type 0 (EV_SYN)
      Event type 1 (EV_KEY)
      Event type 5 (EV_SW)
        Event code 4 (SW_MICROPHONE_INSERT) state 0
    Properties:
    Testing ... (interrupt to exit)
    Event: time 1751449448.185340, type 5 (EV_SW), code 4 (SW_MICROPHONE_INSERT), value 1
    Event: time 1751449448.185340, -------------- SYN_REPORT ------------
    Event: time 1751449448.289477, type 5 (EV_SW), code 4 (SW_MICROPHONE_INSERT), value 0
    Event: time 1751449448.289477, -------------- SYN_REPORT ------------
    Event: time 1751449449.329482, type 5 (EV_SW), code 4 (SW_MICROPHONE_INSERT), value 1
    Event: time 1751449449.329482, -------------- SYN_REPORT ------------

Tested-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>