linux-kernel - Re: [PATCH v4 03/10] pwm: max7360: Add MAX7360 PWM support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z69c1BQHmlbmwUYf@smile.fi.intel.com>
Date: Fri, 14 Feb 2025 17:10:12 +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 v4 03/10] pwm: max7360: Add MAX7360 PWM support

On Fri, Feb 14, 2025 at 12:49:53PM +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.

...

+ bits.h

+ dev_printk.h

> +#include <linux/err.h>


> +#include <linux/math.h>

Other way around, id est you need math64.h (see below).

> +#include <linux/mfd/max7360.h>

+ minmax.h

> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>

> +#include <linux/of.h>

Is this used? Cargo cult?

> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>

+ types.h

...

> +#define MAX7360_PWM_PERIOD_NS			2000000 /* 500 Hz */

Comment is superfluous, if you need HZ units, define the respective one.
Also you can use something like (2 * NSEC_PER_MSEC) which will immediately
gives a hint of how long this is and reduces potential 0:s miscalculations.
This will need time.h

...

> +#define MAX7360_PWM_CTRL_ENABLE(n)		BIT(n)
> +#define MAX7360_PWM_PORT(n)			BIT(n)

Personally I find these macros overkill. The value of them much shorter and
equally readable.

...

> +struct max7360_pwm {

> +	struct device *parent;

Is it not the same as you can derive from regmap?

> +	struct regmap *regmap;

Btw, have you checked the code generation if you place regmap the first in the
structure? It might affect it.

> +};

...

> +	/*
> +	 * Ignore user provided values for period_length_ns and duty_offset_ns:
> +	 * we only support fixed period of MAX7360_PWM_PERIOD_NS and offset of

> +	 * 0.

Easy to read with 0 be on previous line.

> +	 */

> +

No need for this blank line.

> +	duty_steps = mul_u64_u64_div_u64(wf->duty_length_ns, MAX7360_PWM_MAX_RES,
> +					 MAX7360_PWM_PERIOD_NS);

This comes from math64.h

> +
> +	wfhw->duty_steps = min(MAX7360_PWM_MAX_RES, duty_steps);

...

> +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 max7360_pwm *max7360_pwm;
> +	unsigned int val;
> +	int ret;
> +
> +	max7360_pwm = max7360_pwm_from_chip(chip);
> +
> +	val = (wfhw->duty_steps == 0) ? 0 : MAX7360_PWM_CTRL_ENABLE(pwm->hwpwm);
> +	ret = regmap_write_bits(max7360_pwm->regmap, MAX7360_REG_GPIOCTRL,
> +				MAX7360_PWM_CTRL_ENABLE(pwm->hwpwm), val);

> +
> +	if (!ret && wfhw->duty_steps != 0) {
> +		ret = regmap_write(max7360_pwm->regmap, MAX7360_REG_PWM(pwm->hwpwm),
> +				   wfhw->duty_steps);
> +	}
> +
> +	return ret;

Please, improve readability by rewriting like this:

	ret = regmap_write_bits(max7360_pwm->regmap, MAX7360_REG_GPIOCTRL,
				MAX7360_PWM_CTRL_ENABLE(pwm->hwpwm), val);
	if (ret)
		return ret;

	if (wfhw->duty_steps)
		return regmap_write(max7360_pwm->regmap, MAX7360_REG_PWM(pwm->hwpwm),
				    wfhw->duty_steps);

	return 0;

> +}

...

> +static int max7360_pwm_probe(struct platform_device *pdev)
> +{

With

	struct device *dev = &pdev->dev;

all below will look shorter and nicer.

> +	struct max7360_pwm *max7360_pwm;
> +	struct pwm_chip *chip;
> +	int ret;
> +
> +	if (!pdev->dev.parent)
> +		return dev_err_probe(&pdev->dev, -ENODEV, "no parent device\n");
> +
> +	chip = devm_pwmchip_alloc(pdev->dev.parent, MAX7360_NUM_PWMS,
> +				  sizeof(*max7360_pwm));
> +	if (IS_ERR(chip))
> +		return PTR_ERR(chip);
> +	chip->ops = &max7360_pwm_ops;
> +
> +	max7360_pwm = max7360_pwm_from_chip(chip);
> +	max7360_pwm->parent = pdev->dev.parent;
> +
> +	max7360_pwm->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> +	if (!max7360_pwm->regmap)
> +		return dev_err_probe(&pdev->dev, -ENODEV,
> +				     "could not get parent regmap\n");

Will become one line (with the above suggestion).

> +	ret = devm_pwmchip_add(&pdev->dev, chip);

> +	if (ret != 0)

Please, be consistent with the style, and moreover this style is unusual.

> +		return dev_err_probe(&pdev->dev, ret,
> +				     "failed to add PWM chip\n");
> +
> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko