Re: [PATCH v1 1/3] pwm: dwc: Add 16 channel support for Intel Elkhart Lake

Raag Jadav
2024-01-30T10:37:21Z

On Sun, Jan 28, 2024 at 04:53:24PM +0200, Andy Shevchenko wrote:
> On Mon, Jan 22, 2024 at 08:32:36AM +0530, Raag Jadav wrote:
> > Intel Elkhart Lake PSE includes two instances of PWM as a single PCI
> > function with 8 channels each. Add support for the remaining channels.
>
> ...
>
> > +static int dwc_pwm_init(struct device *dev, const struct dwc_pwm_info *info, void __iomem *base)
> > +{
> > + /* Default values for single instance devices */
> > + unsigned int nr = 1, size = 0;
> > + int i, ret;
> > +
> > + /* Fill up values from driver_data, if any */
> > + if (info) {
> > + nr = info->nr;
> > + size = info->size;
> > + }
> > +
> > + for (i = 0; i < nr; i++) {
> > + struct dwc_pwm *dwc;
> > +
> > + dwc = dwc_pwm_alloc(dev);
> > + if (!dwc)
> > + return -ENOMEM;
> > +
> > + dwc->base = base + (i * size);
> > +
> > + ret = devm_pwmchip_add(dev, &dwc->chip);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
>
> Why not doing this slightly differently?
>
> First option: Always provide driver data (info is never NULL).

Allowing empty driver_data would save us from adding dummy info
for single instance devices in the future.

> Second option, have the body of the for-loop be factored to a helper
> dwc_pwm_init_one() and here
>
> if (!info)
> return dwc_pwm_init_one(..., 1, 0);
>
> for (i = 0; i < info->nr; i++) {
> ret = dwc_pwm_init_one(...);
> if (ret)
> return ret;
> }

Considering above, we're looking at something like this.

static int dwc_pwm_init_one(struct device *dev, void __iomem *base, unsigned int size)
{
struct dwc_pwm *dwc;

dwc = dwc_pwm_alloc(dev);
if (!dwc)
return -ENOMEM;

dwc->base = base + size;

return devm_pwmchip_add(dev, &dwc->chip);
}

...

if (info) {
for (i = 0; i < info->nr; i++) {
ret = dwc_pwm_init_one(dev, base, i * info->size);
if (ret)
return ret;
}
} else {
ret = dwc_pwm_init_one(dev, base, 0);
if (ret)
return ret;
}
...

Raag