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

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Message-ID: <20190321102537.GR4615@pendragon.ideasonboard.com>
Date:   Thu, 21 Mar 2019 12:25:37 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
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>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...nel.org>, linux-gpio@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] gpio: pca953x: Configure wake-up path when wake-up
 is enabled

Hi Geert,

Thank you for the patch.

On Wed, Mar 20, 2019 at 11:39:27AM +0100, Geert Uytterhoeven 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.

It would be nice for this to be handled automatically...

> 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.
> 
> 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.
> 
> However, gpio-keys is suspended _after_ gpio-pca953x, breaking the
> scheme :-(
> 
> So depending on topology, this may work, or not...

Could device links help there ?

> ---
>  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);

-- 
Regards,

Laurent Pinchart