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

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Message-ID: <Z9qoGmNKcozbIjeH@smile.fi.intel.com>
Date: Wed, 19 Mar 2025 13:18:50 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: mathieu.dubois-briand@...tlin.com
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kamel Bouhara <kamel.bouhara@...tlin.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Michael Walle <mwalle@...nel.org>, Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-pwm@...r.kernel.org,
	Grégory Clement <gregory.clement@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v5 04/11] pwm: max7360: Add MAX7360 PWM support

On Tue, Mar 18, 2025 at 05:26:20PM +0100, mathieu.dubois-briand@...tlin.com wrote:
> From: Kamel Bouhara <kamel.bouhara@...tlin.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