linux-kernel - Re: [PATCH v4 4/4] pwm: adp5585: Add Analog Devices ADP5585 support

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Date: Mon, 10 Jun 2024 18:28:33 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-pwm@...r.kernel.org,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Lee Jones <lee@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Clark Wang <xiaoning.wang@....com>
Subject: Re: [PATCH v4 4/4] pwm: adp5585: Add Analog Devices ADP5585 support

On Mon, Jun 10, 2024 at 06:06:51PM +0300, Andy Shevchenko wrote:
> Sat, Jun 08, 2024 at 05:16:33PM +0300, Laurent Pinchart kirjoitti:
> > From: Clark Wang <xiaoning.wang@....com>
> > 
> > The ADP5585 is a 10/11 input/output port expander with a built in keypad
> > matrix decoder, programmable logic, reset generator, and PWM generator.
> > This driver supports the PWM function using the platform device
> > registered by the core MFD driver.
> > 
> > The driver is derived from an initial implementation from NXP, available
> > in commit 113113742208 ("MLK-25922-1 pwm: adp5585: add adp5585 PWM
> > support") in their BSP kernel tree. It has been extensively rewritten.
> 
> ...
> 
> > +#define ADP5585_PWM_OSC_FREQ_HZ		1000000U
> 
> (1 * HZ_PER_MHZ) ?
> 
> Variant to use MEGA. Or even #define MHz in units.h if you wish.
> Putting a few 0:s in a row is error prone.

Feel free to send follow-up patches.

Andy, we're reaching a level of nitpicking and yakshaving that even I
can't deal with. I will have to simply ignore the comments I disagree
with.

> ...
> 
> > +	ret = regmap_write(regmap, ADP5585_PWM_OFFT_LOW,
> > +			   off & 0xff);
> > +	if (ret)
> > +		return ret;
> > +	ret = regmap_write(regmap, ADP5585_PWM_OFFT_HIGH,
> > +			   (off >> 8) & 0xff);
> > +	if (ret)
> > +		return ret;
> 
> This is regular I²C regmap, why do you avoid using regmap bulk APIs?
> 
> > +	ret = regmap_write(regmap, ADP5585_PWM_ONT_LOW,
> > +			   on & 0xff);
> > +	if (ret)
> > +		return ret;
> > +	ret = regmap_write(regmap, ADP5585_PWM_ONT_HIGH,
> > +			   (on >> 8) & 0xff);
> > +	if (ret)
> > +		return ret;
> 
> Ditto.
> 
> ...
> 
> > +static int pwm_adp5585_get_state(struct pwm_chip *chip,
> > +				 struct pwm_device *pwm,
> > +				 struct pwm_state *state)
> > +{
> > +	struct regmap *regmap = pwmchip_get_drvdata(chip);
> > +	unsigned int on, off;
> > +	unsigned int val;
> > +
> > +	regmap_read(regmap, ADP5585_PWM_OFFT_LOW, &off);
> > +	regmap_read(regmap, ADP5585_PWM_OFFT_HIGH, &val);
> > +	off |= val << 8;
> 
> Ditto.
> 
> > +	regmap_read(regmap, ADP5585_PWM_ONT_LOW, &on);
> > +	regmap_read(regmap, ADP5585_PWM_ONT_HIGH, &val);
> > +	on |= val << 8;
> 
> Ditto.
> 
> > +	state->duty_cycle = on * (NSEC_PER_SEC / ADP5585_PWM_OSC_FREQ_HZ);
> > +	state->period = (on + off) * (NSEC_PER_SEC / ADP5585_PWM_OSC_FREQ_HZ);
> > +
> > +	state->polarity = PWM_POLARITY_NORMAL;
> > +
> > +	regmap_read(regmap, ADP5585_PWM_CFG, &val);
> > +	state->enabled = !!(val & ADP5585_PWM_EN);
> > +
> > +	return 0;
> 
> Besides that, how do you guarantee that no IO may happen in between of those
> calls? Probably you want a driver explicit lock? In that case, would you still
> want to have a regmap internal lock?
> 
> > +}
> 
> ...
> 
> > +static int adp5585_pwm_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct adp5585_dev *adp5585 = dev_get_drvdata(dev->parent);
> > +	struct pwm_chip *chip;
> > +	int ret;
> > +
> > +	chip = devm_pwmchip_alloc(dev, ADP5585_PWM_CHAN_NUM, 0);
> > +	if (IS_ERR(chip))
> > +		return PTR_ERR(chip);
> 
> > +	device_set_of_node_from_dev(dev, dev->parent);
> 
> Still unclear to me why only few drivers use this.
> 
> > +	pwmchip_set_drvdata(chip, adp5585->regmap);
> > +	chip->ops = &adp5585_pwm_ops;
> > +
> > +	ret = devm_pwmchip_add(dev, chip);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "failed to add PWM chip\n");
> > +
> > +	return 0;
> > +}
> 
> ...
> 
> > +static const struct platform_device_id adp5585_pwm_id_table[] = {
> > +	{ "adp5585-pwm" },
> > +	{ /* Sentinel */ },
> 
> Drop comma. Otherwise it's not a sentinel strictly speaking.
>
> > +};

-- 
Regards,

Laurent Pinchart