Add trivial PWM driver for Argon40 Fan HAT, which is a RaspberryPi
blower fan hat which can be controlled over I2C. Model this device
as a PWM, so the pwm-fan can be attached to it and handle thermal
zones and RPM management in a generic manner.
Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
---
Cc: "Uwe Kleine-König" <ukleinek@xxxxxxxxxx>
Cc: Conor Dooley <conor+dt@xxxxxxxxxx>
Cc: Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-pwm@xxxxxxxxxxxxxxx
Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
---
V2: - Switch to waveform ops
- Add shutdown hook to force the fan to maximum RPM on shutdown
instead of stopping it, to be on the safe side
---
drivers/pwm/Kconfig | 9 +++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-argon-fan-hat.c | 115 ++++++++++++++++++++++++++++++++
3 files changed, 125 insertions(+)
create mode 100644 drivers/pwm/pwm-argon-fan-hat.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 6e113f8b4baf..3ef1757502eb 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -66,6 +66,15 @@ config PWM_APPLE
To compile this driver as a module, choose M here: the module
will be called pwm-apple.
+config PWM_ARGON_FAN_HAT
+ tristate "Argon40 Fan HAT support"
+ depends on I2C && OF
+ help
+ Generic PWM framework driver for Argon40 Fan HAT.
+
+ To compile this driver as a module, choose M here: the module
+ will be called pwm-argon-fan-hat.
+
config PWM_ATMEL
tristate "Atmel PWM support"
depends on ARCH_AT91 || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 96160f4257fc..ff4f47e5fb7a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_PWM) += core.o
obj-$(CONFIG_PWM_AB8500) += pwm-ab8500.o
obj-$(CONFIG_PWM_ADP5585) += pwm-adp5585.o
obj-$(CONFIG_PWM_APPLE) += pwm-apple.o
+obj-$(CONFIG_PWM_ARGON_FAN_HAT) += pwm-argon-fan-hat.o
obj-$(CONFIG_PWM_ATMEL) += pwm-atmel.o
obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM) += pwm-atmel-hlcdc.o
obj-$(CONFIG_PWM_ATMEL_TCB) += pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-argon-fan-hat.c b/drivers/pwm/pwm-argon-fan-hat.c
new file mode 100644
index 000000000000..a26b58ee7f29
--- /dev/null
+++ b/drivers/pwm/pwm-argon-fan-hat.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Marek Vasut
+ *
+ * Limitations:
+ * - no support for offset/polarity
+ * - fixed duty cycle, period changes from 0Hz..120kHz
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/pwm.h>
+
+static int argon_fan_hat_round_waveform_tohw(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ const struct pwm_waveform *wf,
+ void *_wfhw)
+{
+ u8 *wfhw = _wfhw;
+
+ *wfhw = DIV_ROUND_CLOSEST_ULL(wf->duty_length_ns * 100, wf->period_length_ns);
+
+ return 0;
+}
+
+static int argon_fan_hat_round_waveform_fromhw(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ const void *_wfhw,
+ struct pwm_waveform *wf)
+{
+ const u8 *wfhw = _wfhw;
+
+ /* 1 step of this hardware is cca. 1200 Hz increase in frequency */
+ wf->period_length_ns = DIV64_U64_ROUND_UP(NSEC_PER_SEC, *wfhw * 1200);
+ wf->duty_length_ns = wf->period_length_ns / 10;
+ wf->duty_offset_ns = 0;
+
+ return 0;
+}
+
+static int argon_fan_hat_write_waveform(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ const void *_wfhw)
+{
+ struct i2c_client *i2c = pwmchip_get_drvdata(chip);
+ const u8 *wfhw = _wfhw;
+ u8 tx[2] = { 0x80, *wfhw };
+ struct i2c_msg msg = {
+ .addr = i2c->addr,
+ .len = 2,
+ .buf = tx,
+ };
+
+ return (i2c_transfer(i2c->adapter, &msg, 1) == 1) ? 0 : -EINVAL;
+}
+
+static const struct pwm_ops argon_fan_hat_pwm_ops = {
+ .sizeof_wfhw = sizeof(u8),
+ .round_waveform_fromhw = argon_fan_hat_round_waveform_fromhw,
+ .round_waveform_tohw = argon_fan_hat_round_waveform_tohw,
+ .write_waveform = argon_fan_hat_write_waveform,
+};
+
+static int argon_fan_hat_i2c_probe(struct i2c_client *i2c)
+{
+ struct pwm_chip *pc = devm_pwmchip_alloc(&i2c->dev, 1, 0);
+ int ret;
+
+ if (IS_ERR(pc))
+ return PTR_ERR(pc);
+
+ pc->ops = &argon_fan_hat_pwm_ops;
+ pwmchip_set_drvdata(pc, i2c);
+
+ ret = devm_pwmchip_add(&i2c->dev, pc);
+ if (ret)
+ return dev_err_probe(&i2c->dev, ret, "Could not add PWM chip\n");
+
+ return 0;
+}
+
+static void argon_fan_hat_i2c_shutdown(struct i2c_client *i2c)
+{
+ u8 tx[2] = { 0x80, 0x64 };
+ struct i2c_msg msg = {
+ .addr = i2c->addr,
+ .len = 2,
+ .buf = tx,
+ };
+
+ i2c_transfer(i2c->adapter, &msg, 1);
+}
+
+static const struct of_device_id argon_fan_hat_dt_ids[] = {
+ { .compatible = "argon40,fan-hat" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, argon_fan_hat_dt_ids);
+
+static struct i2c_driver argon_fan_hat_driver = {
+ .driver = {
+ .name = "argon-fan-hat",
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+ .of_match_table = argon_fan_hat_dt_ids,
+ },
+ .probe = argon_fan_hat_i2c_probe,
+ .shutdown = argon_fan_hat_i2c_shutdown,
+};
+
+module_i2c_driver(argon_fan_hat_driver);
+
+MODULE_AUTHOR("Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("Argon40 Fan HAT");
+MODULE_LICENSE("GPL");
--
2.47.2
