linux-kernel - Re: [PATCH 3/6] gpio/omap: remove suspend_wakeup field from struct gpio

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Date:	Tue, 28 Feb 2012 15:09:05 +0530
From:	"DebBarma, Tarun Kanti" <tarun.kanti@...com>
To:	Kevin Hilman <khilman@...com>
Cc:	linux-omap@...r.kernel.org, grant.likely@...retlab.ca,
	tony@...mide.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/6] gpio/omap: remove suspend_wakeup field from struct gpio_bank

On Tue, Feb 28, 2012 at 5:24 AM, Kevin Hilman <khilman@...com> wrote:
> Tarun Kanti DebBarma <tarun.kanti@...com> writes:
>
>> Since we already have bank->context.wake_en to keep track
>> of gpios which are wakeup enabled, there is no need to have
>> this field any more.
>>
>> Signed-off-by: Tarun Kanti DebBarma <tarun.kanti@...com>
>
> I'm not crazy about this change...
>
>> ---
>>  drivers/gpio/gpio-omap.c |   11 +++++------
>>  1 files changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>> index 64f15d5..b62e861 100644
>> --- a/drivers/gpio/gpio-omap.c
>> +++ b/drivers/gpio/gpio-omap.c
>> @@ -53,7 +53,6 @@ struct gpio_bank {
>>       void __iomem *base;
>>       u16 irq;
>>       u16 virtual_irq_start;
>> -     u32 suspend_wakeup;
>>       u32 non_wakeup_gpios;
>>       u32 enabled_non_wakeup_gpios;
>>       struct gpio_regs context;
>> @@ -497,9 +496,9 @@ static int _set_gpio_wakeup(struct gpio_bank *bank, int gpio, int enable)
>>
>>       spin_lock_irqsave(&bank->lock, flags);
>>       if (enable)
>> -             bank->suspend_wakeup |= gpio_bit;
>> +             bank->context.wake_en |= gpio_bit;
>>       else
>> -             bank->suspend_wakeup &= ~gpio_bit;
>> +             bank->context.wake_en &= ~gpio_bit;
>
> The bank->context values are expected to be copies of the actual
> register contents, and here that is clearly not the case.
Right, it should have been this:

        if (enable)
-               bank->suspend_wakeup |= gpio_bit;
+               bank->context.wake_en |= gpio_bit;
        else
-               bank->suspend_wakeup &= ~gpio_bit;
+               bank->context.wake_en &= ~gpio_bit;
+
+       __raw_writel(bank->context.wake_en, bank->base + bank->regs->wkup_en);

>
> With this change, you're using the context register to track changes
> that you *might* eventually write to the register.
The above change ensures that bank->context.wake_en reflects the
latest register value.
There are two distinct paths through which bank->context.wake_en is
updated now, viz:
Path1:-
chip.irq_set_type() --> gpio_irq_type() --> _set_gpio_triggering() -->
set_gpio_trigger()

Path2:-
chip.irq_set_wake() --> gpio_wake_enable() --> irq_set_wake()

>
> IMO, this is more confusing than having a separate field to track this.
So, there is no need have a separate field to keep track of this.
I hope my understanding is right.
--
Tarun

>
> Kevin
>
>>       spin_unlock_irqrestore(&bank->lock, flags);
>>
>> @@ -772,7 +771,7 @@ static int omap_mpuio_suspend_noirq(struct device *dev)
>>
>>       spin_lock_irqsave(&bank->lock, flags);
>>       bank->context.wake_en = __raw_readl(mask_reg);
>> -     __raw_writel(0xffff & ~bank->suspend_wakeup, mask_reg);
>> +     __raw_writel(0xffff & ~bank->context.wake_en, mask_reg);
>>       spin_unlock_irqrestore(&bank->lock, flags);
>>
>>       return 0;
>> @@ -1137,12 +1136,12 @@ static int omap_gpio_suspend(struct device *dev)
>>       if (!bank->mod_usage || !bank->loses_context)
>>               return 0;
>>
>> -     if (!bank->regs->wkup_en || !bank->suspend_wakeup)
>> +     if (!bank->regs->wkup_en || !bank->context.wake_en)
>>               return 0;
>>
>>       spin_lock_irqsave(&bank->lock, flags);
>>       _gpio_rmw(base, bank->regs->wkup_en, 0xffffffff, 0);
>> -     _gpio_rmw(base, bank->regs->wkup_en, bank->suspend_wakeup, 1);
>> +     _gpio_rmw(base, bank->regs->wkup_en, bank->context.wake_en, 1);
>>       spin_unlock_irqrestore(&bank->lock, flags);
>>
>>       return 0;
--
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