Rockchip SARADC — pineport

The Rockchip SARADC path is a 10-bit successive-approximation ADC. On the PinePhone Pro it reads the volume-button resistor divider on channel

On PineTab2 the imported Linux DTS uses RK3566/RK3568 SARADC channel 0 for the same VOL+ / VOL- role. Both halves of that path — the SARADC provider and the adc-keys consumer — are local to this tree.

Identity

Property	Value
Block	RK3399 / RK356x SARADC
MMIO base	PPP: `0xff100000`; PineTab2: inherited RK356x `fe720000`
Channels	6 (10-bit each)
Reference	1.8 V (`RK_SARADC_DEFAULT_VREF_UV = 1800000`)
Clock rate	1 MHz (`RK_SARADC_CLK_RATE`)
DTS compatible	`rockchip,rk3399-saradc`, `rockchip,rk3568-saradc`
Linux driver	`drivers/iio/adc/rockchip_saradc.c`

PinePhone Pro channel map:

Channel	Function
1	Volume button divider (VOL+ / VOL-)
others	Unused on PPP

PineTab2 channel map:

Channel	Function
0	Volume button divider (VOL+ / VOL-)

Live capture from KEY_VOLUMEUP / KEY_VOLUMEDOWN:

Press	Voltage
VOLUMEUP	0–21 mV
VOLUMEDOWN	0.30–0.63 V
Idle (no press)	≈1.79 V

Driver

● working

Two cooperating drivers live under our overlay:

src/sys/arm64/rockchip/rk_saradc.c — 276 lines. Polled, blocking-style channel reads behind a microsecond delay loop (RK_SARADC_POLL_DELAY_US = 1, RK_SARADC_POLL_RETRIES = 2000). Exposes a kobj method (header rk_saradc.h) so consumers in the same kld can request a channel conversion synchronously.
src/sys/arm64/rockchip/rk_adc_keys.c — adc-keys consumer. Iterates child OFW nodes for thresholds and keycodes, polls the SARADC every 100 ms by default, and emits evdev events. Sysctl debug knobs landed in 2612871 Add ADC keys debug sysctls .

The whole stack is local because mainline FreeBSD has no SARADC ADC framework consumer to plug into; we wired the two-driver pair against each other directly via a kobj method rather than waiting for an in-tree IIO/ADC abstraction.

Bring-up started in 32e626d Add PPP SARADC volume keys and refresh status docs . The PineTab2 speculative step adds the RK3568-compatible provider match and richer rk_adc_keys debug sysctls so the tablet’s channel-0 ladder can be verified without guesswork.

Verification

# Sway volume OSD reacts to VOL+ / VOL-, and:
sysctl dev.rk_saradc.0
sysctl dev.rk_adc_keys.0

The OSD path is documented in the Status essay; volume buttons are listed there as one of the resolved input items.

Open work

Confirm PineTab2 rockchip,rk3568-saradc attach and channel-0 readings on hardware.
No DMA or interrupt-driven mode — polled is fine at 10 Hz, would need rework for higher-rate analog work (none planned).

Status essay (14) — where the volume buttons sit in the working-input inventory.
Hardware reference — Input and sensors row.
HARDWARE.md — SARADC is checked off under Input & Sensors → Done.

Identity

Driver

Verification

Open work

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