Re: [PATCH v5 04/11] pwm: max7360: Add MAX7360 PWM support

Andy Shevchenko
2025-03-19T11:18:59Z

On Tue, Mar 18, 2025 at 05:26:20PM +0100, mathieu.dubois-briand@bootlin.com wrote:
> From: Kamel Bouhara <kamel.bouhara@bootlin.com>
>
> Add driver for Maxim Integrated MAX7360 PWM controller, supporting up to
> 8 independent PWM outputs.

...

> +#include <linux/bits.h>
> +#include <linux/dev_printk.h>
> +#include <linux/err.h>
> +#include <linux/math64.h>
> +#include <linux/mfd/max7360.h>
> +#include <linux/minmax.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +#include <linux/time.h>
> +#include <linux/types.h>

...

> +static void max7360_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct regmap *regmap;
> + struct device *dev;
> +
> + regmap = pwmchip_get_drvdata(chip);
> + dev = regmap_get_device(regmap);

Huh?!

> +}

...

> +static int max7360_pwm_round_waveform_tohw(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + const struct pwm_waveform *wf,
> + void *_wfhw)

I would expect other way around, i.e. naming with leading underscore(s) to be
private / local. Ditto for all similar cases.

...

> +static int max7360_pwm_write_waveform(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + const void *_wfhw)
> +{
> + const struct max7360_pwm_waveform *wfhw = _wfhw;
> + struct regmap *regmap;
> + unsigned int val;
> + int ret;
> +
> + regmap = pwmchip_get_drvdata(chip);
> + val = (wfhw->enabled) ? BIT(pwm->hwpwm) : 0;

Redundant parentheses.

> + ret = regmap_write_bits(regmap, MAX7360_REG_GPIOCTRL, BIT(pwm->hwpwm), val);
> + if (ret)
> + return ret;
> +
> + if (wfhw->duty_steps)
> + return regmap_write(regmap, MAX7360_REG_PWM(pwm->hwpwm), wfhw->duty_steps);
> +
> + return 0;
> +}

...

> +static int max7360_pwm_read_waveform(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + void *_wfhw)
> +{
> + struct max7360_pwm_waveform *wfhw = _wfhw;
> + struct regmap *regmap;
> + unsigned int val;
> + int ret;
> +
> + regmap = pwmchip_get_drvdata(chip);
> +
> + ret = regmap_read(regmap, MAX7360_REG_GPIOCTRL, &val);
> + if (ret)
> + return ret;
> +
> + if (val & BIT(pwm->hwpwm)) {
> + wfhw->enabled = true;

Also can be (but up to you)

wfhw->enabled = val & BIT(pwm->hwpwm);
if (wfhw->enabled) {

And also see below. Perhaps it is not a good suggestion after all.

> + ret = regmap_read(regmap, MAX7360_REG_PWM(pwm->hwpwm), &val);
> + wfhw->duty_steps = val;

Set to a garbage in case of error, why?

> + } else {
> + wfhw->enabled = false;
> + wfhw->duty_steps = 0;
> + }
> +
> + return ret;
> +}

...

> +static int max7360_pwm_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct pwm_chip *chip;
> + struct regmap *regmap;
> + int ret;
> +
> + if (!dev->parent)
> + return dev_err_probe(dev, -ENODEV, "no parent device\n");

Why? Code most likely will fail on the regmap retrieval. Just do that first.

> + chip = devm_pwmchip_alloc(dev->parent, MAX7360_NUM_PWMS, 0);

This is quite worrying. The devm_ to parent makes a lot of assumptions that may
not be realised. If you really need this, it has to have a very good comment
explaining why and object lifetimes.

> + if (IS_ERR(chip))
> + return PTR_ERR(chip);
> + chip->ops = &max7360_pwm_ops;
> +
> + regmap = dev_get_regmap(dev->parent, NULL);
> + if (!regmap)
> + return dev_err_probe(dev, -ENODEV, "could not get parent regmap\n");
> +
> + pwmchip_set_drvdata(chip, regmap);
> +
> + ret = devm_pwmchip_add(dev, chip);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to add PWM chip\n");
> +
> + return 0;
> +}

--
With Best Regards,
Andy Shevchenko