Subject: [PATCH v2] gpio/omap: fix off-mode bug: clear debounce clock enable mask on free/reset

From: [email-masked] (Jon Hunter)
Date: Wed, 24 Oct 2012 17:54:15 -0500

On 10/24/2012 12:10 PM, Kevin Hilman wrote:
> From: Kevin Hilman <[email-masked]>
> 
> When a GPIO bank is freed or shutdown, ensure that the banks
> dbck_enable_mask is cleared also.  Otherwise, context restore on
> subsequent off-mode transition will restore previous value from the
> shadow copies (bank->context.debounce*) leading to mismatch state
> between driver state and hardware state.
> 
> This was discovered when board code was doing
> 
>   gpio_request_one()
>   gpio_set_debounce()
>   gpio_free()
> 
> which was leaving the GPIO debounce settings in a confused state.  If
> that GPIO bank is subsequently used with off-mode enabled, bogus state
> would be restored, leaving GPIO debounce enabled which then prevented
> the CORE powerdomain from transitioning.
> 
> To fix, ensure that bank->dbck_enable_mask is cleared when the bank
> is freed/shutdown so debounce state doesn't persist.
> 
> Special thanks to Grazvydas Ignotas for pointing out a bug in an
> earlier version that would've disabled debounce on any runtime PM
> transition.
> 
> Reported-by: Paul Walmsley <[email-masked]>
> Cc: Igor Grinberg <[email-masked]>
> Cc: Grazvydas Ignotas <[email-masked]>
> Signed-off-by: Kevin Hilman <[email-masked]>
> ---
> v2: only clear mask in free/shutdown, not in runtime PM paths, 
>     clarified changelog   
> Applies on v3.7-rc2.
> 
>  drivers/gpio/gpio-omap.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index 94cbc84..113b167 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -539,6 +539,7 @@ static void _reset_gpio(struct gpio_bank *bank, int gpio)
>  	_set_gpio_irqenable(bank, gpio, 0);
>  	_clear_gpio_irqstatus(bank, gpio);
>  	_set_gpio_triggering(bank, GPIO_INDEX(bank, gpio), IRQ_TYPE_NONE);
> +	bank->dbck_enable_mask = 0;
>  }

Does this need to be ...

+	bank->dbck_enable_mask &= ~(GPIO_BIT(bank, gpio));
+	_gpio_dbck_disable(bank);

There could be more than one gpio using debounce and so we should only
clear the appropriate bit. Also after clearing a bit we could see if we
can disable the debounce clock too.

Cheers
Jon