linux-kernel - Re: [PATCH v2 4/4] pwm: adp5585: Add Analog Devices ADP5585 support

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Date: Wed, 29 May 2024 09:22:54 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-pwm@...r.kernel.org, 
	Alexandru Ardelean <alexandru.ardelean@...log.com>, 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 v2 4/4] pwm: adp5585: Add Analog Devices ADP5585 support

On Tue, May 28, 2024 at 11:27 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> On Tue, May 28, 2024 at 10:41:51PM +0300, Andy Shevchenko wrote:
> > Tue, May 28, 2024 at 10:03:14PM +0300, Laurent Pinchart kirjoitti:

..

> > > +#define ADP5585_PWM_OSC_FREQ_HZ            1000000U
> >
> > (1 * HZ_PER_MHZ) ?
>
> If we had an MHZ macro I would use 1 * MHZ, but I don't think HZ_PER_MHZ
> improves readability here.

We have MEGA. HZ is already the suffix in this definition.

> > > +#define ADP5585_PWM_MIN_PERIOD_NS  (2ULL * NSEC_PER_SEC / ADP5585_PWM_OSC_FREQ_HZ)
> > > +#define ADP5585_PWM_MAX_PERIOD_NS  (2ULL * 0xffff * NSEC_PER_SEC / ADP5585_PWM_OSC_FREQ_HZ)
> >
> > Wouldn't be better to use GENMASK() or (BIT(x) - 1) notation to show that
> > the limit is due to HW register bits in use?
>
> I think that would decrease readability to be honest.

I think it improves the robustness of the code. I always fail to count
3,4,5,6 f:s in those masks, using BIT()/GENMASK() notation makes it
better.

..

> > > +   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;
> > > +   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;
> >
> > Can be proper __le16/__be16 be used in conjunction with regmap bulk API?
>
> What I would really like is regmap growing an API similar to
> include/media/v4l2-cci.h. Any volunteer ? :-)

So, the answer here is yes?

..

> > > +   regmap_read(regmap, ADP5585_PWM_OFFT_LOW, &off);
> > > +   regmap_read(regmap, ADP5585_PWM_OFFT_HIGH, &val);
> > > +   off |= val << 8;
> > > +
> > > +   regmap_read(regmap, ADP5585_PWM_ONT_LOW, &on);
> > > +   regmap_read(regmap, ADP5585_PWM_ONT_HIGH, &val);
> > > +   on |= val << 8;
> >
> > As per above, can it be converted to use proper __le16/__be16 type and
> > regmap bulk API?
>
> As there are only 2 registers, I think that's a bit overkill really.

I do not think so. It increases readability (less LoCs) and improves a
lot of understanding of the hardware layout from reading the code.
Please, consider using it.

..

> > > +   device_set_of_node_from_dev(dev, dev->parent);
> >
> > Why this one? What's wrong with device_set_node()?
>
> See my reply to 3/4.

See additional questions there as well.

-- 
With Best Regards,
Andy Shevchenko