Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank_count

["Varadarajan, Charulatha" <charu@ti.com>]

Felipe,

On Sat, Feb 4, 2012 at 21:38, Felipe Balbi <balbi@ti.com> wrote:
>
> Hi,
>
> On Fri, Feb 03, 2012 at 09:50:19AM -0800, Kevin Hilman wrote:
> > Felipe Balbi <balbi@ti.com> writes:
> >
> > [...]
> >
> > >> >This question remains. Why do we need those funtions ?
> > >>
> > >> These functions are called from the CPUIdle path so outside the scope
> > >> of the GPIO driver. These are part of a bunch of nasty PM hacks we
> > >> are doing in the CPU idle loop. We are in the process of getting rid
> > >> of most of them, but it looks like some are still needed.
> > >
> > > Too bad. I can see that the gpio pm implementation seems a bit
> > > "peculiar". I mean, pm does reference counting and yet the driver has
> > > checks to prevent multiple gets and puts on a single bank (meaning that
> > > pm counter will be either 0 or 1 at any point in time).
> > >
> > > To me it looks like those functions are there in order to forcefully put
> > > PER power domain in OFF because drivers are always holding a reference
> > > to their gpios (drivers generally gpio_request() on probe() and
> > > gpio_free() on remove()).
> > >
> > > Looks like the entire pm implementation on OMAP gpio driver has always
> > > considered only the fact that gpios can be requested and freed, but
> > > never that we want the system to go to OFF even while gpios are
> > > requested, because we have I/O PAD wakeups. At some point that has to be
> > > sorted out because that HACK is quite ugly :-)
> > >
> > > I'll see if I find some time to go over the interactions between
> > > gpio-omap.c and pm24x.c and pm34xx.c any of these days, but I can't
> > > promise anything ;-)
> >
> > If you look at the state of these prepare/resume hacks at the end of
> > this series, you'll see that they are significantly cleaner and do
> > nothing but call the runtime PM hooks.
>
> sure, definitely.
>
> > We have explored several ways to get rid of them completely in the idle
> > path but have not yet come up with a clean way, but this series gets us
> > a long ways towards that goal.
>
> have you thought about being a bit more aggressive at when to
> runtime_get and runtime_put ?
>
> I didn't test below (will do probably on monday), but I think this will
> help keeping GPIO block always suspended, and only wake it up when truly
> needed. That way, you could, at some point, remove that list_head
> because by the time you reach CPUIdle path, GPIO module is already
> suspended. That's the theory at least, gotta run it first on silicon to
> be sure
>
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index 4273401..2dd9ced 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -537,12 +537,7 @@ static int omap_gpio_request(struct gpio_chip *chip, unsigned offset)
>        struct gpio_bank *bank = container_of(chip, struct gpio_bank, chip);
>        unsigned long flags;
>
> -       /*
> -        * If this is the first gpio_request for the bank,
> -        * enable the bank module.
> -        */
> -       if (!bank->mod_usage)
> -               pm_runtime_get_sync(bank->dev);
> +       pm_runtime_get_sync(bank->dev);

bank->mod_usage check is used to take care of doing pm_runtime_get*/put* only
if all the GPIOs in a particular bank are enabled or disabled respectively.

With the above change, pm_runtime_put*/get* would be called for every
gpio_request()
/_free() (that is, for upto 32 pins in OMAP3/4) in a bank irrespective
of whether other
GPIO pins are enabled or disabled in the same bank. Hence it is
required to have a
check based on mod_usage.

I agree with your approach of aggressively doing pm_runtime* calls and this
was discussed internally sometime ago.

-V Charulatha

>
>        spin_lock_irqsave(&bank->lock, flags);
>        /* Set trigger to none. You need to enable the desired trigger with
> @@ -572,6 +567,8 @@ static int omap_gpio_request(struct gpio_chip *chip, unsigned offset)
>
>        spin_unlock_irqrestore(&bank->lock, flags);
>
> +       pm_runtime_put(bank->dev);
> +
>        return 0;
>  }
>
> @@ -581,6 +578,8 @@ static void omap_gpio_free(struct gpio_chip *chip, unsigned offset)
>        void __iomem *base = bank->base;
>        unsigned long flags;
>
> +       pm_runtime_get_sync(bank->dev);
> +
>        spin_lock_irqsave(&bank->lock, flags);
>
>        if (bank->regs->wkup_en) {
> @@ -606,12 +605,7 @@ static void omap_gpio_free(struct gpio_chip *chip, unsigned offset)
>        _reset_gpio(bank, bank->chip.base + offset);
>        spin_unlock_irqrestore(&bank->lock, flags);
>
> -       /*
> -        * If this is the last gpio to be freed in the bank,
> -        * disable the bank module.
> -        */
> -       if (!bank->mod_usage)
> -               pm_runtime_put(bank->dev);
> +       pm_runtime_put(bank->dev);
>  }
>
>  /*
> @@ -707,9 +701,11 @@ static void gpio_irq_shutdown(struct irq_data *d)
>        struct gpio_bank *bank = irq_data_get_irq_chip_data(d);
>        unsigned long flags;
>
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        _reset_gpio(bank, gpio);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
>  }
>
>  static void gpio_ack_irq(struct irq_data *d)
> @@ -717,7 +713,9 @@ static void gpio_ack_irq(struct irq_data *d)
>        unsigned int gpio = d->irq - IH_GPIO_BASE;
>        struct gpio_bank *bank = irq_data_get_irq_chip_data(d);
>
> +       pm_runtime_get_sync(bank->dev);
>        _clear_gpio_irqstatus(bank, gpio);
> +       pm_runtime_put(bank->dev);
>  }
>
>  static void gpio_mask_irq(struct irq_data *d)
> @@ -726,10 +724,12 @@ static void gpio_mask_irq(struct irq_data *d)
>        struct gpio_bank *bank = irq_data_get_irq_chip_data(d);
>        unsigned long flags;
>
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        _set_gpio_irqenable(bank, gpio, 0);
>        _set_gpio_triggering(bank, GPIO_INDEX(bank, gpio), IRQ_TYPE_NONE);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
>  }
>
>  static void gpio_unmask_irq(struct irq_data *d)
> @@ -740,6 +740,7 @@ static void gpio_unmask_irq(struct irq_data *d)
>        u32 trigger = irqd_get_trigger_type(d);
>        unsigned long flags;
>
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        if (trigger)
>                _set_gpio_triggering(bank, GPIO_INDEX(bank, gpio), trigger);
> @@ -753,6 +754,7 @@ static void gpio_unmask_irq(struct irq_data *d)
>
>        _set_gpio_irqenable(bank, gpio, 1);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
>  }
>
>  static struct irq_chip gpio_irq_chip = {
> @@ -836,17 +838,26 @@ static int gpio_input(struct gpio_chip *chip, unsigned offset)
>        unsigned long flags;
>
>        bank = container_of(chip, struct gpio_bank, chip);
> +       pm_runtime_get_sync(bank->dev);
> +
>        spin_lock_irqsave(&bank->lock, flags);
>        _set_gpio_direction(bank, offset, 1);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
> +
>        return 0;
>  }
>
>  static int gpio_is_input(struct gpio_bank *bank, int mask)
>  {
>        void __iomem *reg = bank->base + bank->regs->direction;
> +       u32 val;
>
> -       return __raw_readl(reg) & mask;
> +       pm_runtime_get_sync(bank->dev);
> +       val = __raw_readl(reg) & mask;
> +       pm_runtime_put(bank->dev);
> +
> +       return val;
>  }
>
>  static int gpio_get(struct gpio_chip *chip, unsigned offset)
> @@ -856,15 +867,20 @@ static int gpio_get(struct gpio_chip *chip, unsigned offset)
>        int gpio;
>        u32 mask;
>
> +       int val;
>        gpio = chip->base + offset;
>        bank = container_of(chip, struct gpio_bank, chip);
>        reg = bank->base;
>        mask = GPIO_BIT(bank, gpio);
>
> +       pm_runtime_get_sync(bank->dev);
>        if (gpio_is_input(bank, mask))
> -               return _get_gpio_datain(bank, gpio);
> +               val = _get_gpio_datain(bank, gpio);
>        else
> -               return _get_gpio_dataout(bank, gpio);
> +               val = _get_gpio_dataout(bank, gpio);
> +       pm_runtime_put(bank->dev);
> +
> +       return val;
>  }
>
>  static int gpio_output(struct gpio_chip *chip, unsigned offset, int value)
> @@ -873,10 +889,14 @@ static int gpio_output(struct gpio_chip *chip, unsigned offset, int value)
>        unsigned long flags;
>
>        bank = container_of(chip, struct gpio_bank, chip);
> +
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        bank->set_dataout(bank, offset, value);
>        _set_gpio_direction(bank, offset, 0);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
> +
>        return 0;
>  }
>
> @@ -894,9 +914,11 @@ static int gpio_debounce(struct gpio_chip *chip, unsigned offset,
>                        dev_err(bank->dev, "Could not get gpio dbck\n");
>        }
>
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        _set_gpio_debounce(bank, offset, debounce);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
>
>        return 0;
>  }
> @@ -907,9 +929,12 @@ static void gpio_set(struct gpio_chip *chip, unsigned offset, int value)
>        unsigned long flags;
>
>        bank = container_of(chip, struct gpio_bank, chip);
> +
> +       pm_runtime_get_sync(bank->dev);
>        spin_lock_irqsave(&bank->lock, flags);
>        bank->set_dataout(bank, offset, value);
>        spin_unlock_irqrestore(&bank->lock, flags);
> +       pm_runtime_put(bank->dev);
>  }
>
>  static int gpio_2irq(struct gpio_chip *chip, unsigned offset)
> @@ -1330,7 +1355,8 @@ void omap2_gpio_prepare_for_idle(int pwr_mode)
>
>                bank->power_mode = pwr_mode;
>
> -               pm_runtime_put_sync_suspend(bank->dev);
> +               if (!pm_runtime_suspended(bank->dev))
> +                       pm_runtime_suspend(bank->dev);
>        }
>  }
>
> @@ -1342,7 +1368,8 @@ void omap2_gpio_resume_after_idle(void)
>                if (!bank->mod_usage || !bank->loses_context)
>                        continue;
>
> -               pm_runtime_get_sync(bank->dev);
> +               if (pm_runtime_suspended(bank->dev))
> +                       pm_runtime_resume(bank->dev);
>        }
>  }
>
>
> --
> balbi