linux-kernel - Re: [PATCH] pinctrl: intel: save HOSTSW

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Date:   Wed, 3 Apr 2019 16:06:40 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Chris Chiu <chiu@...lessm.com>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Daniel Drake <drake@...lessm.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:PIN CONTROL SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: [PATCH] pinctrl: intel: save HOSTSW_OWN register over
 suspend/resume

On Wed, Apr 03, 2019 at 03:06:43PM +0800, Chris Chiu wrote:
> On Tue, Apr 2, 2019 at 7:58 PM Andy Shevchenko
> <andriy.shevchenko@...el.com> wrote:

> > Instead you may need to loop over each pin in the part of the group related to
> > one 32-bit HOSTSW_OWN register (i.e. 8, see PADOWN_*() macros in the driver),
> > check if it's requested and break a loop. If loop index is off-by-one a limit,
> > nothing to do, otherwise restore hostown register.
> >
> > More pedantic approach is to collect the mask inside the loop and apply it.
> >
> > The check function name is gpiochip_is_requested().
> >
> > (One of Intel's drivers which is using that at ->resume() is
> >  drivers/gpio/gpio-lynxpoint.c)
> >
> > P.S. I prefer pedantic approach. The simplification one is showed in order to
> > give you an idea.

> Thanks for your great comment. I remove the useless hostown save function
> and make the following change in ->resume() to detect and restore the abnormal
> HOSTSW_OWN. Please help comment if there're still problems. Thanks.

> +               base = community->regs + community->hostown_offset;
> +               for (gpp = 0; gpp < community->ngpps; gpp++) {
> +                       const struct intel_padgroup *padgrp =
> &community->gpps[i];
> +                       unsigned int requested = 0;
> +                       int j;
> +
> +                       if (padgrp->gpio_base < 0)
> +                               continue;

> +
> +                       for (j = 0; j < padgrp->size; j++)
> +                               if
> (gpiochip_is_requested(&pctrl->chip, padgrp->gpio_base + j))
> +                                       requested |= BIT(j);
> +

This better to make as a separate helper function

static u32 intel_gpio_is_requested(chip, base, size)
{
	u32 requested = 0;
	unsigned int i;

	for () {
		if ()
			requested |= BIT();
	}
	return requested;
}

(Note u32 as a type)

> +                       if (requested) {
> +                               if (communities[i].hostown[gpp] !=
> readl(base + gpp * 4)) {
> +
> writel(communities[i].hostown[gpp], base + gpp * 4);

The idea here not to check this at all, but rather apply a mask.

u32 value;

...
value = readl();
value = (value & ~requested) | (hostown[gpp] & requested);
writel(value);

> +                                       dev_warn(dev, "hostown been
> changed during resume\n");
> +                                       dev_dbg(dev, "restored hostown
> %d/%u %#08x\n", i, gpp,
> +                                               readl(base + gpp * 4));
> +                               }
> +                       }
> +               }

-- 
With Best Regards,
Andy Shevchenko