Date:   Tue, 8 Jan 2019 14:21:19 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Michal Simek <michal.simek@...inx.com>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     Nava kishore Manne <navam@...inx.com>,
        Josh Cartwright <josh.cartwright@...com>,
        "monstr@...str.eu" <monstr@...str.eu>,
        Peter Crosthwaite <peter.crosthwaite@...inx.com>,
        Borsodi Petr <Petr.Borsodi@...z>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Rob Herring <robherring2@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Sören Brinkmann <soren.brinkmann@...inx.com>,
        Shubhrajyoti Datta <shubhraj@...inx.com>
Subject: Re: [PATCH 2/8] gpio: zynq: Wakeup gpio controller when it is used as
 IRQ controller

On 07. 01. 19 16:42, Thomas Petazzoni wrote:
> Hello,
> 
> I am reviving this old thread, because the proposed patch (almost)
> solves the problem I recently reported with the bad interaction of
> runtime PM with the Zynq GPIO driver (see
> https://www.spinics.net/lists/linux-gpio/msg35437.html).
> 
> On Mon, 14 Aug 2017 16:33:09 +0200, Michal Simek wrote:
> 
>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
>> index 9568708a550b..a08a044fa4aa 100644
>> --- a/drivers/gpio/gpiolib.c
>> +++ b/drivers/gpio/gpiolib.c
>> @@ -1647,14 +1647,22 @@ static void gpiochip_irq_unmap(struct irq_domain
>> *d, unsigned int irq)
>>  static int gpiochip_irq_reqres(struct irq_data *d)
>>  {
>>         struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
>> +       int ret;
>>
>>         if (!try_module_get(chip->gpiodev->owner))
>>                 return -ENODEV;
>>
>> +       ret = pm_runtime_get_sync(chip->parent);
>> +       if (ret < 0) {
>> +               module_put(chip->gpiodev->owner);
>> +               return ret;
>> +       }
>> +
>>         if (gpiochip_lock_as_irq(chip, d->hwirq)) {
>>                 chip_err(chip,
>>                         "unable to lock HW IRQ %lu for IRQ\n",
>>                         d->hwirq);
>> +               pm_runtime_put(chip->parent);
>>                 module_put(chip->gpiodev->owner);
>>                 return -EINVAL;
>>         }
>> @@ -1666,6 +1674,7 @@ static void gpiochip_irq_relres(struct irq_data *d)
>>         struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
>>
>>         gpiochip_unlock_as_irq(chip, d->hwirq);
>> +       pm_runtime_put(chip->parent);
>>         module_put(chip->gpiodev->owner);
>>  }
> 
> This patch almost solves the problem. It doesn't work as-is, because it
> assumes that runtime PM is used by all GPIO controllers, which is not
> the case. When runtime PM is not enabled, pm_runtime_get_sync() fails
> with -EACCES, and the whole gpiochip_irq_reqres() function aborts.
> 
> The following patch works fine in my case (a MMC card detect signal is
> connected to a pin of a PCA GPIO expander over I2C, whose INT# pin is
> itself connected to a GPIO pin of the Zynq SoC).
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 20887c62fbb3..bd9a81fc8d56 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -27,6 +27,7 @@
>  #include <linux/kfifo.h>
>  #include <linux/poll.h>
>  #include <linux/timekeeping.h>
> +#include <linux/pm_runtime.h>
>  #include <uapi/linux/gpio.h>
>  
>  #include "gpiolib.h"
> @@ -3540,12 +3541,23 @@ int gpiochip_reqres_irq(struct gpio_chip *chip, unsigned int offset)
>         if (!try_module_get(chip->gpiodev->owner))
>                 return -ENODEV;
>  
> +       if (pm_runtime_enabled(chip->parent)) {
> +               ret = pm_runtime_get_sync(chip->parent);
> +               if (ret < 0) {
> +                       module_put(chip->gpiodev->owner);
> +                       return ret;
> +               }
> +       }
> +
>         ret = gpiochip_lock_as_irq(chip, offset);
>         if (ret) {
>                 chip_err(chip, "unable to lock HW IRQ %u for IRQ\n", offset);
> +               if (pm_runtime_enabled(chip->parent))
> +                       pm_runtime_put(chip->parent);
>                 module_put(chip->gpiodev->owner);
>                 return ret;
>         }
> +
>         return 0;
>  }
>  EXPORT_SYMBOL_GPL(gpiochip_reqres_irq);
> @@ -3553,6 +3565,8 @@ EXPORT_SYMBOL_GPL(gpiochip_reqres_irq);
>  void gpiochip_relres_irq(struct gpio_chip *chip, unsigned int offset)
>  {
>         gpiochip_unlock_as_irq(chip, offset);
> +       if (pm_runtime_enabled(chip->parent))
> +               pm_runtime_put(chip->parent);
>         module_put(chip->gpiodev->owner);
>  }
>  EXPORT_SYMBOL_GPL(gpiochip_relres_irq);
> 
> However, I must say that from a design perspective, I am not a big fan
> of this solution. Indeed for the normal GPIO ->request() and ->free()
> hooks, it is currently the GPIO driver itself that is responsible for
> runtime PM get/put, so it would be weird to have the runtime PM get/put
> for the IRQ request/free be done by the GPIO core.
> 
> I believe that either the GPIO core should be in charge of the entire
> runtime PM interaction, or it should entirely be the responsibility of
> each GPIO controller driver. Having a mixed solution seems very
> confusing.
> 
> Let me know which direction should be taken so that I can submit a
> proper patch to hopefully resolve this issue.

I think it is up to Linus to say which way he wants to go. We found that
way which omap is using.

In connection to this old patch. I think I have tested it later and
wasn't able to replicate it that's why I stop keep track on this.

Thanks,
Michal

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