linux-kernel - [PATCH v4 0/3] hwmon: (adt7475) duty cycle configuration

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Date: Wed, 29 May 2024 10:56:35 +1200
From: Chris Packham <chris.packham@...iedtelesis.co.nz>
To: jdelvare@...e.com,
	linux@...ck-us.net,
	robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	ukleinek@...nel.org
Cc: linux-hwmon@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v4 0/3] hwmon: (adt7475) duty cycle configuration

I have a system that has very over spec'd fans so the amount of noise when they
run at 100% duty cycle is considerable. We have userspace monitoring tools that
will configure appropriate fan control parameters but there is a bit of a delay
between the kernel loading the driver and the userland tools catching up to
configure the fan control. This series adds device properties that allow the
PWM duty cycle to be specified via device properties so the PWM duty cycle can
be reduced as soon as possible.

This series attempts to setup the adt7475 as a pwm provider so that we can
specify these properties. The devicetree support was reasonably straight
forward (example usage is in the binding patch). I struggled to get the ACPI
version working well and in the end the code had to distinguish between the
of_node and other case. The ASL I've ended up with is

    Device (ADT0)
    {
        Name (_HID, "PRP0001")
        Name (_CRS, ResourceTemplate () {
            I2cSerialBusV2 (0x2E, ControllerInitiated,
                            100000, AddressingMode7Bit,
                            "^^CH00", 0x00,
                            ResourceConsumer, , Exclusive, )
        })
        Name (_DSD, Package () {
            ToUUID (UUID_DEVICE_PROPERTIES),
            Package () {
                Package () { "compatible", "adi,adt7476" },
                Package () { "#pwm-cells", 4 },
            },
        })
        Device (FAN0)
        {
            Name (_ADR, 0)
            Name (_DSD, Package () {
                ToUUID (UUID_DEVICE_PROPERTIES),
                Package () {
                    Package () { "pwms", Package () { 0, 22500, 1, 50 } },
                }
            })
        }
        Device (FAN1)
        {
            Name (_ADR, 0)
            Name (_DSD, Package () {
                ToUUID (UUID_DEVICE_PROPERTIES),
                Package () {
                    Package () { "pwms", Package () { 2, 22500, 1, 50 } },
                }
            })
        }
    }

If had to introduce a code path that parses that because try as I might I could
not convince fwnode_property_get_reference_args() to fetch the information out
of the ACPI data. If I've missed something obvious please let me know.

Chris Packham (3):
  dt-bindings: hwmon: Add adt7475 fan/pwm properties
  dt-bindings: hwmon: adt7475: Deprecate adi,pwm-active-state
  hwmon: (adt7475) Add support for configuring initial PWM state

 .../devicetree/bindings/hwmon/adt7475.yaml    |  27 ++++-
 drivers/hwmon/adt7475.c                       | 112 ++++++++++++++++++
 2 files changed, 137 insertions(+), 2 deletions(-)

-- 
2.45.1