pwm: argon-fan-hat: Add Argon40 Fan HAT support

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@mailbox.org>
Link: https://lore.kernel.org/r/20250629220757.936212-3-marek.vasut+renesas@mailbox.org
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 6e113f8b4baf293284f017bc22fbc162633bb2fc..3ef1757502ebd92b30584cd10611311a0fbfc03b 100644 (file)
--- 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 96160f4257fcb0e0951581af0090615c0edf5260..ff4f47e5fb7a0dbac72c12de82c3773e5582db6d 100644 (file)
--- 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 (file)
index 0000000..2c59bd1
--- /dev/null
+++ b/drivers/pwm/pwm-argon-fan-hat.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Marek Vasut
+ *
+ * Limitations:
+ * - no support for offset/polarity
+ * - fixed 30 kHz period
+ *
+ * Argon Fan HAT https://argon40.com/products/argon-fan-hat
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/pwm.h>
+
+#define ARGON40_FAN_HAT_PERIOD_NS      33333   /* ~30 kHz */
+
+#define ARGON40_FAN_HAT_REG_DUTY_CYCLE 0x80
+
+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;
+
+       if (wf->duty_length_ns > ARGON40_FAN_HAT_PERIOD_NS)
+               *wfhw = 100;
+       else
+               *wfhw = mul_u64_u64_div_u64(wf->duty_length_ns, 100, ARGON40_FAN_HAT_PERIOD_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;
+
+       wf->period_length_ns = ARGON40_FAN_HAT_PERIOD_NS;
+       wf->duty_length_ns = DIV64_U64_ROUND_UP(wf->period_length_ns * *wfhw, 100);
+       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;
+
+       return i2c_smbus_write_byte_data(i2c, ARGON40_FAN_HAT_REG_DUTY_CYCLE, *wfhw);
+}
+
+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,
+       /*
+        * The controller does not provide any way to read info back,
+        * reading from the controller stops the fan, therefore there
+        * is no .read_waveform here.
+        */
+};
+
+static int argon_fan_hat_i2c_probe(struct i2c_client *i2c)
+{
+       struct pwm_chip *chip = devm_pwmchip_alloc(&i2c->dev, 1, 0);
+       int ret;
+
+       if (IS_ERR(chip))
+               return PTR_ERR(chip);
+
+       chip->ops = &argon_fan_hat_pwm_ops;
+       pwmchip_set_drvdata(chip, i2c);
+
+       ret = devm_pwmchip_add(&i2c->dev, chip);
+       if (ret)
+               return dev_err_probe(&i2c->dev, ret, "Could not add PWM chip\n");
+
+       return 0;
+}
+
+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,
+};
+
+module_i2c_driver(argon_fan_hat_driver);
+
+MODULE_AUTHOR("Marek Vasut <marek.vasut+renesas@mailbox.org>");
+MODULE_DESCRIPTION("Argon40 Fan HAT");
+MODULE_LICENSE("GPL");