Hello Marek,
I wonder how this device works in rpios, I didn't find a matching driver
(but I also didn't try more than two minutes).
On Wed, Jun 11, 2025 at 12:07:27AM +0200, Marek Vasut wrote:
> diff --git a/drivers/pwm/pwm-argon-fan-hat.c b/drivers/pwm/pwm-argon-fan-hat.c
> new file mode 100644
> index 000000000000..3d04abdbd349
> --- /dev/null
> +++ b/drivers/pwm/pwm-argon-fan-hat.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2025 Marek Vasut
> + */
* Limitations:
* - fixed period (which?)
* - no support for offset/polarity
If you can find out if it completes a period when reconfigured that
would also be nice to document.
This device is really trivial, but for completeness' sake: If there is a
data sheet publicly available, please add a link here.
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/pwm.h>
> +
> +static int argon_fan_hat_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state)
Can you please implement the new-style callbacks?
> +{
> + struct i2c_client *i2c = pwmchip_get_drvdata(chip);
> + u8 tx[2] = { 0x80, state->enabled ? pwm_get_relative_duty_cycle(state, 100) : 0 };
This is too simple. I won't go into details about the right algorithm
for .apply() as I want you to implement .round_waveform_tohw() +
.round_waveform_fromhw() + .read_waveform() + .write_waveform() anyhow.
For .round_waveform_tohw() you have to know the actual period length and
then use something like:
duty = wf->duty_length_ns;
if (duty > ARGON_FAN_HAT_PERIOD)
duty = ARGON_FAN_HAT_PERIOD;
duty_percent = 100 * duty / ARGON_FAN_HAT_PERIOD;
> + struct i2c_msg msg = {
> + .addr = i2c->addr,
> + .len = 2,
> + .buf = tx,
> + };
> +
> + if (state->polarity != PWM_POLARITY_NORMAL)
> + return -EINVAL;
> +
> + return (i2c_transfer(i2c->adapter, &msg, 1) == 1) ? 0 : -EINVAL;
> +}
> +
> +static const struct pwm_ops argon_fan_hat_pwm_ops = {
> + .apply = argon_fan_hat_pwm_apply,
Can you read back the configuration? If yes then please implement
.read_waveform().
> +};
> +
> +static int argon_fan_hat_i2c_probe(struct i2c_client *i2c)
> +{
> + struct pwm_chip *pc = devm_pwmchip_alloc(&i2c->dev, 1, 0);
> +
> + if (IS_ERR(pc))
> + return PTR_ERR(pc);
> +
> + pc->ops = &argon_fan_hat_pwm_ops;
> + pwmchip_set_drvdata(pc, i2c);
> +
> + return devm_pwmchip_add(&i2c->dev, pc);
Error message on failure please. (-> dev_err_probe())
> +}
> +
> +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,
> +};
TIL about PROBE_PREFER_ASYNCHRONOUS.
Best regards
Uwe
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