linux-kernel - Re: [PATCH RFC] gpio: pca953x: Configure wake-up path when wake-up is enabled

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Date:   Thu, 4 Apr 2019 10:54:45 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        linux-gpio@...r.kernel.org, Linux PM <linux-pm@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] gpio: pca953x: Configure wake-up path when wake-up is enabled

On Wed, 20 Mar 2019 at 11:39, Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
>
> If a device is part of the wake-up path, it should indicate this by
> setting its power.wakeup_path field.  This allows the genpd core code to
> keep the device enabled during system suspend when needed.
>
> As regulators powering devices are not handled by genpd, the driver
> handles these itself, and thus must skip regulator control when the
> device is part of the wake-up path.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> Note that I don't really need this on the Renesas Ebisu-4D board, as
> there is no regulator or PM Domain controlling power to the GPIO
> expander on that board.  I did want to have all wake-up path processing
> implemented in the driver for completeness, and did test its behavior
> with gpio-keys configured as a wake-up source.

All above makes perfect sense to me.

>
> However, while this approach is known to work fine on other boards, with
> other GPIO and interrupt controllers (gpio-rcar, irq-renesas-irqc,
> irq-renesas-intc-irqpin), it wouldn't work on Ebisu-4D, due to different
> device suspend ordering.
>
> The proper ordering is:
>   1. When gpio-keys is suspended, its suspend handler calls
>      enable_irq_wake(), invoking pca953x_irq_set_wake(), and causing
>      pca953x_chip.wakeup_path to be incremented,
>   2. When gpio-pca953x is suspended, it checks pca953x_chip.wakeup_path,
>      and marks the device to be part of the wake-up path.

Right.

>
> However, gpio-keys is suspended _after_ gpio-pca953x, breaking the
> scheme :-(

Would it make sense to fixup the ordering issue via creating a
parent/child relationship or setting up a device link?

>
> So depending on topology, this may work, or not...
> ---
>  drivers/gpio/gpio-pca953x.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> index 88c94d155e218535..349d0ccb5285a6c4 100644
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -153,6 +153,7 @@ struct pca953x_chip {
>         u8 irq_trig_fall[MAX_BANK];
>         struct irq_chip irq_chip;
>  #endif
> +       atomic_t wakeup_path;
>
>         struct i2c_client *client;
>         struct gpio_chip gpio_chip;
> @@ -581,6 +582,11 @@ static int pca953x_irq_set_wake(struct irq_data *d, unsigned int on)
>         struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
>         struct pca953x_chip *chip = gpiochip_get_data(gc);
>
> +       if (on)
> +               atomic_inc(&chip->wakeup_path);
> +       else
> +               atomic_dec(&chip->wakeup_path);
> +
>         return irq_set_irq_wake(chip->client->irq, on);
>  }
>
> @@ -1100,7 +1106,10 @@ static int pca953x_suspend(struct device *dev)
>
>         regcache_cache_only(chip->regmap, true);
>
> -       regulator_disable(chip->regulator);
> +       if (atomic_read(&chip->wakeup_path))
> +               device_set_wakeup_path(dev);
> +       else
> +               regulator_disable(chip->regulator);
>
>         return 0;
>  }
> @@ -1110,10 +1119,12 @@ static int pca953x_resume(struct device *dev)
>         struct pca953x_chip *chip = dev_get_drvdata(dev);
>         int ret;
>
> -       ret = regulator_enable(chip->regulator);
> -       if (ret != 0) {
> -               dev_err(dev, "Failed to enable regulator: %d\n", ret);
> -               return 0;
> +       if (!atomic_read(&chip->wakeup_path)) {
> +               ret = regulator_enable(chip->regulator);
> +               if (ret != 0) {
> +                       dev_err(dev, "Failed to enable regulator: %d\n", ret);
> +                       return 0;
> +               }
>         }
>
>         regcache_cache_only(chip->regmap, false);
> --
> 2.17.1
>

Looks good to me!

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe