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Message-ID: <tpqebtepsnp5slukdiwn3rrcrrxj7cl22vrblrldo4x73e42py@yslhryqvsacb>
Date: Mon, 25 Aug 2025 10:11:59 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Rob Herring <robh@...nel.org>
Cc: Nuno Sá <nuno.sa@...log.com>,
linux-hwmon@...r.kernel.org, linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, Lee Jones <lee@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>,
Jonathan Corbet <corbet@....net>, Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 1/6] dt-binbings: mfd: Add bindings for the LTC4283 Swap
Controller
On Thu, Aug 14, 2025 at 04:57:24PM -0500, Rob Herring wrote:
> On Thu, Aug 14, 2025 at 11:52:23AM +0100, Nuno Sá wrote:
> > The LTC4283 is a negative voltage hot swap controller that drives an
> > external N-channel MOSFET to allow a board to be safely inserted and
> > removed from a live backplane.
>
> What's a binbing?
>
> When you fix that, don't say 'bindings' twice in the subject. Subject
> space is precious.
oh, sure...
>
> >
> > Main usage is as an Hardware Monitoring device. However, it has up to 8
> > pins that can be configured and used as GPIOs and hence, the device can
> > also be a GPIO controller.
> >
> > Signed-off-by: Nuno Sá <nuno.sa@...log.com>
> > ---
> > .../devicetree/bindings/mfd/adi,ltc4283.yaml | 85 ++++++++++++++++++++++
> > MAINTAINERS | 7 ++
> > 2 files changed, 92 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/mfd/adi,ltc4283.yaml b/Documentation/devicetree/bindings/mfd/adi,ltc4283.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..c5e8aec887d9cfad9052a7c28783396efd6804a9
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mfd/adi,ltc4283.yaml
> > @@ -0,0 +1,85 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mfd/adi,ltc4283.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: LTC4283 I2C Negative Voltage Hot Swap Controller
> > +
> > +maintainers:
> > + - Nuno Sá <nuno.sa@...log.com>
> > +
> > +description: |
> > + The LTC4283 negative voltage hot swap controller drives an external N-channel
> > + MOSFET to allow a board to be safely inserted and removed from a live
> > + backplane.
> > +
> > + https://www.analog.com/media/en/technical-documentation/data-sheets/ltc4283.pdf
> > +
> > +properties:
> > + compatible:
> > + enum:
> > + - adi,ltc4283
> > +
> > + reg:
> > + maxItems: 1
> > +
> > + gpio:
> > + $ref: /schemas/gpio/adi,ltc4283.yaml
> > + hwmon:
> > + $ref: /schemas/hwmon/adi,ltc4283.yaml
>
> This patch has to come after these are added. However...
>
Yeah, I realized that when I got your bot build failure email.
> > +
> > + adi,gpio-pins:
> > + description:
> > + The pins to use as GPIOs. The device has 4 ADIO and 4 PGIO
> > + pins than can be used as GPIOs. The ADIO pins are numbered from 0 to 3
> > + and the PGIO pins are numbered from 4 to 7.
> > + $ref: /schemas/types.yaml#/definitions/uint32-array
> > + minItems: 1
> > + maxItems: 8
> > + items:
> > + minimum: 0
> > + maximum: 7
> > +
> > +dependencies:
> > + gpio:
> > + - adi,gpio-pins
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - hwmon
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + i2c {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + swap-controller@15 {
> > + compatible = "adi,ltc4283";
> > + reg = <0x15>;
> > +
> > + /* pgio1 to pgio4 as gpios */
> > + adi,gpio-pins = <0 1 2 3>;
> > +
> > + gpio {
> > + compatible = "adi,ltc4283-gpio";
> > + gpio-controller;
> > + #gpio-cells = <2>;
> > + };
> > +
> > + hwmon {
> > + compatible = "adi,ltc4283-hwmon";
> > +
> > + adi,rsense-nano-ohms = <500>;
>
> Seems like a current sense resistor might be a common thing.
>
At least ltc4282 has the same property so I can add a common property if
you want me too.
> > + adi,current-limit-sense-microvolt = <25000>;
> > + adi,current-limit-foldback-factor = <10>;
> > + adi,cooling-delay-ms = <8190>;
> > + adi,fet-bad-timer-delay-ms = <512>;
>
> All these child node properties can be moved to the parent node.
>
Hmm, if I move to the auxiliary device, this will "fix" itself but just
out of curiosity, why should it be on the parent node? These properties
only make sense for the hwmon device.
- Nuno Sá
> > + };
> > + };
> > + };
> > +...
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index e90710a9b40d7b32c151472a9ac3b02efd95f346..413bb77d5eebe2b51aa9c3af86e7cfd5ab142044 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -14500,6 +14500,13 @@ F: Documentation/devicetree/bindings/hwmon/adi,ltc4282.yaml
> > F: Documentation/hwmon/ltc4282.rst
> > F: drivers/hwmon/ltc4282.c
> >
> > +lTC4283 HARDWARE MONITOR AND GPIO DRIVER
> > +M: Nuno Sá <nuno.sa@...log.com>
> > +L: linux-hwmon@...r.kernel.org
> > +L: linux-gpio@...r.kernel.org
> > +S: Supported
> > +F: Documentation/devicetree/bindings/mfd/adi,ltc4283.yaml
> > +
> > LTC4286 HARDWARE MONITOR DRIVER
> > M: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>
> > L: linux-hwmon@...r.kernel.org
> >
> > --
> > 2.50.1
> >
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