[PATCH V2] gpio: rcar: Fix level interrupt handling

[PATCH V2] gpio: rcar: Fix level interrupt handling

[Valentine Barshak]

According to the manual, if a port is set for level detection using
the corresponding bit in the edge/level select register and an external
level interrupt signal is asserted, the corresponding bit in INTDT
does not use the FF to hold the input.
Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
corresponding bits in the INTDT register. Instead, when an external
input signal is stopped, the corresponding bit in INTDT is cleared
automatically.

Since the INTDT bit cannot be cleared for the level interrupts until
the interrupt signal is stopped, we end up with the infinite loop
when using deferred (threaded) IRQ handling.

Since a deferred interrupt is disabled by the low-level handler and
re-enabled only when the deferred handler is completed, Fix the issue
by dropping disabled interrupts from the pending mask as suggested by
Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Changes in V2:
* Drop disabled interrupts from pending mask altogether instead of
  dropping level interrupts one by one once they get handled.

Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
---
 drivers/gpio/gpio-rcar.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
index d3f15ae..fd2d827 100644
--- a/drivers/gpio/gpio-rcar.c
+++ b/drivers/gpio/gpio-rcar.c
@@ -169,7 +169,8 @@ static irqreturn_t gpio_rcar_irq_handler(int irq, void *dev_id)
 	u32 pending;
 	unsigned int offset, irqs_handled = 0;
 
-	while ((pending = gpio_rcar_read(p, INTDT))) {
+	while ((pending = gpio_rcar_read(p, INTDT) &
+			  gpio_rcar_read(p, INTMSK))) {
 		offset = __ffs(pending);
 		gpio_rcar_write(p, INTCLR, BIT(offset));
 		generic_handle_irq(irq_find_mapping(p->irq_domain, offset));
-- 
1.8.3.1

Re: [PATCH V2] gpio: rcar: Fix level interrupt handling

[Valentine]

On 11/29/2013 10:04 PM, Valentine Barshak wrote:
> According to the manual, if a port is set for level detection using
> the corresponding bit in the edge/level select register and an external
> level interrupt signal is asserted, the corresponding bit in INTDT
> does not use the FF to hold the input.
> Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
> corresponding bits in the INTDT register. Instead, when an external
> input signal is stopped, the corresponding bit in INTDT is cleared
> automatically.
>
> Since the INTDT bit cannot be cleared for the level interrupts until
> the interrupt signal is stopped, we end up with the infinite loop
> when using deferred (threaded) IRQ handling.
>
> Since a deferred interrupt is disabled by the low-level handler and
> re-enabled only when the deferred handler is completed, Fix the issue
> by dropping disabled interrupts from the pending mask as suggested by
> Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> Changes in V2:
> * Drop disabled interrupts from pending mask altogether instead of
>    dropping level interrupts one by one once they get handled.
>
> Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
> ---
>   drivers/gpio/gpio-rcar.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
> index d3f15ae..fd2d827 100644
> --- a/drivers/gpio/gpio-rcar.c
> +++ b/drivers/gpio/gpio-rcar.c
> @@ -169,7 +169,8 @@ static irqreturn_t gpio_rcar_irq_handler(int irq, void *dev_id)
>   	u32 pending;
>   	unsigned int offset, irqs_handled = 0;
>
> -	while ((pending = gpio_rcar_read(p, INTDT))) {
> +	while ((pending = gpio_rcar_read(p, INTDT) &
> +			  gpio_rcar_read(p, INTMSK))) {
>   		offset = __ffs(pending);
>   		gpio_rcar_write(p, INTCLR, BIT(offset));
>   		generic_handle_irq(irq_find_mapping(p->irq_domain, offset));
>

Laurent, Magnus,
do you have any concerns about fixing the level IRQ's as proposed here?

I'm more inclined to re-read the registers instead of caching the pending value
  pending = gpio_rcar_read(p, INTDT) & gpio_rcar_read(p, INTMSK));
and dropping bits inside the while loop
  pending &= ~BIT(offset);

I think this could help to catch new interrupts while processing previous ones.
It also makes minimum change to the original logic.

Please let me know if you think it's not good enough and the cached "pending" value
(or any other approach) should be used instead.

Thanks,
Val.

Re: [PATCH V2] gpio: rcar: Fix level interrupt handling

[Laurent Pinchart]

Hi Valentine,

On Monday 09 December 2013 23:25:00 Valentine wrote:
> On 11/29/2013 10:04 PM, Valentine Barshak wrote:
> > According to the manual, if a port is set for level detection using
> > the corresponding bit in the edge/level select register and an external
> > level interrupt signal is asserted, the corresponding bit in INTDT
> > does not use the FF to hold the input.
> > Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
> > corresponding bits in the INTDT register. Instead, when an external
> > input signal is stopped, the corresponding bit in INTDT is cleared
> > automatically.
> > 
> > Since the INTDT bit cannot be cleared for the level interrupts until
> > the interrupt signal is stopped, we end up with the infinite loop
> > when using deferred (threaded) IRQ handling.
> > 
> > Since a deferred interrupt is disabled by the low-level handler and
> > re-enabled only when the deferred handler is completed, Fix the issue
> > by dropping disabled interrupts from the pending mask as suggested by
> > Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > 
> > Changes in V2:
> > * Drop disabled interrupts from pending mask altogether instead of
> > 
> >    dropping level interrupts one by one once they get handled.
> > 
> > Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
> > ---
> > 
> >   drivers/gpio/gpio-rcar.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
> > index d3f15ae..fd2d827 100644
> > --- a/drivers/gpio/gpio-rcar.c
> > +++ b/drivers/gpio/gpio-rcar.c
> > @@ -169,7 +169,8 @@ static irqreturn_t gpio_rcar_irq_handler(int irq, void
> > *dev_id)
> >   	u32 pending;
> >   	unsigned int offset, irqs_handled = 0;
> > 
> > -	while ((pending = gpio_rcar_read(p, INTDT))) {
> > +	while ((pending = gpio_rcar_read(p, INTDT) &
> > +			  gpio_rcar_read(p, INTMSK))) {
> >   		offset = __ffs(pending);
> >   		gpio_rcar_write(p, INTCLR, BIT(offset));
> >   		generic_handle_irq(irq_find_mapping(p->irq_domain, offset));
> 
> Laurent, Magnus,
> do you have any concerns about fixing the level IRQ's as proposed here?
> 
> I'm more inclined to re-read the registers instead of caching the pending
> value pending = gpio_rcar_read(p, INTDT) & gpio_rcar_read(p, INTMSK)); and
> dropping bits inside the while loop
>   pending &= ~BIT(offset);
> 
> I think this could help to catch new interrupts while processing previous
> ones. It also makes minimum change to the original logic.
> 
> Please let me know if you think it's not good enough and the cached
> "pending" value (or any other approach) should be used instead.

I would have used the caching approach myself as it makes the loop simpler and 
any external interrupt occuring after the registers are read would be 
processed by a new interrupt handler call, but your approach should work fine 
as well, so I have no reason to complain.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

-- 
Regards,

Laurent Pinchart

Re: [PATCH V2] gpio: rcar: Fix level interrupt handling

[Magnus Damm]

On Tue, Dec 10, 2013 at 4:25 AM, Valentine
<valentine.barshak@cogentembedded.com> wrote:
> On 11/29/2013 10:04 PM, Valentine Barshak wrote:
>>
>> According to the manual, if a port is set for level detection using
>> the corresponding bit in the edge/level select register and an external
>> level interrupt signal is asserted, the corresponding bit in INTDT
>> does not use the FF to hold the input.
>> Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
>> corresponding bits in the INTDT register. Instead, when an external
>> input signal is stopped, the corresponding bit in INTDT is cleared
>> automatically.
>>
>> Since the INTDT bit cannot be cleared for the level interrupts until
>> the interrupt signal is stopped, we end up with the infinite loop
>> when using deferred (threaded) IRQ handling.
>>
>> Since a deferred interrupt is disabled by the low-level handler and
>> re-enabled only when the deferred handler is completed, Fix the issue
>> by dropping disabled interrupts from the pending mask as suggested by
>> Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>
>> Changes in V2:
>> * Drop disabled interrupts from pending mask altogether instead of
>>    dropping level interrupts one by one once they get handled.
>>
>> Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
>> ---
>>   drivers/gpio/gpio-rcar.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
>> index d3f15ae..fd2d827 100644
>> --- a/drivers/gpio/gpio-rcar.c
>> +++ b/drivers/gpio/gpio-rcar.c
>> @@ -169,7 +169,8 @@ static irqreturn_t gpio_rcar_irq_handler(int irq, void
>> *dev_id)
>>         u32 pending;
>>         unsigned int offset, irqs_handled = 0;
>>
>> -       while ((pending = gpio_rcar_read(p, INTDT))) {
>> +       while ((pending = gpio_rcar_read(p, INTDT) &
>> +                         gpio_rcar_read(p, INTMSK))) {
>>                 offset = __ffs(pending);
>>                 gpio_rcar_write(p, INTCLR, BIT(offset));
>>                 generic_handle_irq(irq_find_mapping(p->irq_domain,
>> offset));
>>
>
> Laurent, Magnus,
> do you have any concerns about fixing the level IRQ's as proposed here?

No concerns here, thanks for your help!

Acked-by: Magnus Damm <damm@opensource.se>

Re: [PATCH V2] gpio: rcar: Fix level interrupt handling

[Linus Walleij]

On Fri, Nov 29, 2013 at 7:04 PM, Valentine Barshak
<valentine.barshak@cogentembedded.com> wrote:

> According to the manual, if a port is set for level detection using
> the corresponding bit in the edge/level select register and an external
> level interrupt signal is asserted, the corresponding bit in INTDT
> does not use the FF to hold the input.
> Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
> corresponding bits in the INTDT register. Instead, when an external
> input signal is stopped, the corresponding bit in INTDT is cleared
> automatically.
>
> Since the INTDT bit cannot be cleared for the level interrupts until
> the interrupt signal is stopped, we end up with the infinite loop
> when using deferred (threaded) IRQ handling.
>
> Since a deferred interrupt is disabled by the low-level handler and
> re-enabled only when the deferred handler is completed, Fix the issue
> by dropping disabled interrupts from the pending mask as suggested by
> Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> Changes in V2:
> * Drop disabled interrupts from pending mask altogether instead of
>   dropping level interrupts one by one once they get handled.
>
> Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>

This v2 version applied to fixes with Laurent's and Magnus' ACKs,
tell me if it also need to go into -stable.

Yours,
Linus Walleij

Re: [PATCH V2] gpio: rcar: Fix level interrupt handling

[Magnus Damm]

On Fri, Dec 13, 2013 at 4:54 AM, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Fri, Nov 29, 2013 at 7:04 PM, Valentine Barshak
> <valentine.barshak@cogentembedded.com> wrote:
>
>> According to the manual, if a port is set for level detection using
>> the corresponding bit in the edge/level select register and an external
>> level interrupt signal is asserted, the corresponding bit in INTDT
>> does not use the FF to hold the input.
>> Thus, writing 1 to the corresponding bits in INTCLR cannot clear the
>> corresponding bits in the INTDT register. Instead, when an external
>> input signal is stopped, the corresponding bit in INTDT is cleared
>> automatically.
>>
>> Since the INTDT bit cannot be cleared for the level interrupts until
>> the interrupt signal is stopped, we end up with the infinite loop
>> when using deferred (threaded) IRQ handling.
>>
>> Since a deferred interrupt is disabled by the low-level handler and
>> re-enabled only when the deferred handler is completed, Fix the issue
>> by dropping disabled interrupts from the pending mask as suggested by
>> Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>
>> Changes in V2:
>> * Drop disabled interrupts from pending mask altogether instead of
>>   dropping level interrupts one by one once they get handled.
>>
>> Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
>
> This v2 version applied to fixes with Laurent's and Magnus' ACKs,
> tell me if it also need to go into -stable.

Thanks for your help, Linus! I don't think there is any need to involve -stable.

Cheers,

/ magnus