On Fri, 31 Jan 2025 15:34:43 +0200 Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote: > Support ROHM BD79124 ADC. > > Quite usual stuff. 12-bit, 8-channel ADC with threshold monitoring. > > Except that: > - each ADC input pin can be configured as a general purpose output. > - manually starting an ADC conversion and reading the result would > require the I2C _master_ to do clock stretching(!) for the duration > of the conversion... Let's just say this is not well supported. > - IC supports 'autonomous measurement mode' and storing latest results > to the result registers. This mode is used by the driver due to the > "peculiar" I2C when doing manual reads. > > I sent this as an RFC because I implemented the pin purposing (GPO/ADC) > using pinmux - which I've never done for upstream stuff before. Hence > it's better to ask if this makes sense, or if there is better way to go. > Anyways, resulted drivers spread to 3 subsystems (MFD, pinctrl and IIO) In principle nothing against pin mux for this. There are other options though if pin mux ends up being too complex. - provide ADC channels in the binding channel@x etc. Anything else is freely available as a GPIO. Normal GPIO bindings etc for those. The channel bit is common on SoC ADC anyway where we don't want to expose channels that aren't wired out. For combined ADC GPIO chips we normally don't bother with an MFD. Just host the gpio driver in the ADC one unless there is a strong reasons someone will put this down for GPIO usage only. > > Furthermore, the GPO functionality has not been (properly) tested. I'll > do more testing for v2 if this pinmux approach is appropriate. > > Furthermore, because the ADC uses this continuous autonomous measuring, > and because the IC keeps producing new 'out of window' IRQs if > measurements are out of window - the driver disables the event when > sending one. This prevents generating storm of events, but it also > requires users to reconfigure / re-enable an event if they wish to > continue monitoring after receiving one. Again I am not sure if this is > the best way to handle such HW - so better to ask for an opinion than a > nose bleed, right? Maybe the next version will no longer be a RFC :) Oddly I thought we had ABI for this but not finding it. We basically want a thing that lets us say don't allow a repeat event for X seconds. Then we set a timer and reenable the interrupt after that time. I think there are drivers doing this but can't find one right now :( It's close to _timeout used for gesture detection. > > --- > > Matti Vaittinen (5): > dt-bindings: ROHM BD79124 ADC/GPO > mfd: Add ROHM BD79124 ADC/GPO > iio: adc: Support ROHM BD79124 ADC > pinctrl: Support ROHM BD79124 pinmux / GPO > MAINTAINERS: Add ROHM BD79124 ADC/GPO > > .../devicetree/bindings/mfd/rohm,bd79124.yaml | 111 +++ > MAINTAINERS | 8 + > drivers/iio/adc/Kconfig | 10 + > drivers/iio/adc/Makefile | 1 + > drivers/iio/adc/rohm-bd79124-adc.c | 890 ++++++++++++++++++ > drivers/mfd/Kconfig | 12 + > drivers/mfd/Makefile | 1 + > drivers/mfd/rohm-bd79124.c | 165 ++++ > drivers/pinctrl/Kconfig | 11 + > drivers/pinctrl/Makefile | 1 + > drivers/pinctrl/pinctrl-bd79124.c | 276 ++++++ > include/linux/mfd/rohm-bd79124.h | 32 + > 12 files changed, 1518 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mfd/rohm,bd79124.yaml > create mode 100644 drivers/iio/adc/rohm-bd79124-adc.c > create mode 100644 drivers/mfd/rohm-bd79124.c > create mode 100644 drivers/pinctrl/pinctrl-bd79124.c > create mode 100644 include/linux/mfd/rohm-bd79124.h > > > base-commit: 5bc55a333a2f7316b58edc7573e8e893f7acb532
