linux-kernel - [RFC PATCH 0/5] Support ROHM BD79124 ADC/GPO

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Message-ID: <cover.1738328714.git.mazziesaccount@gmail.com>
Date: Fri, 31 Jan 2025 15:34:43 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Nuno Sa <nuno.sa@...log.com>, David Lechner <dlechner@...libre.com>,
	Dumitru Ceclan <mitrutzceclan@...il.com>,
	Trevor Gamblin <tgamblin@...libre.com>,
	Matteo Martelli <matteomartelli3@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: [RFC PATCH 0/5] Support ROHM BD79124 ADC/GPO

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).

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 :)

---

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
-- 
2.48.1


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