[RFC] Fix shared irq trigger-flags conflict when old irqaction uses IRQF_TRIGGER_NONE

[RFC] Fix shared irq trigger-flags conflict when old irqaction uses IRQF_TRIGGER_NONE

[Hans de Goede]

While writing a driver for the INT0002 ACPI device found on Intel
Bay and Cherry Trail devices I hit the following error:

"genirq: Flags mismatch irq 9. 00000084 (INT0002) vs. 00000080 (acpi)"

This is caused by drivers/acpi/osl.c first doing:

request_irq(irq, acpi_irq, IRQF_SHARED, "acpi", acpi_irq)

While the irqdata for the irq contains no trigger flags, resulting
in an irqaction with IRQF_TRIGGER_NONE.

And then the INT0002 driver I'm working on calling platform_get_irq
which does: irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);

And then request_irq(irq, ..., IRQF_SHARED, ...) on the irq returned
by platform_get_irq causes the error quoted above.

Arguably the genirq code should not hit the shared irq trigger-flags
mismatch code if the old irqaction has IRQF_TRIGGER_NONE as flags.

This patch is an attempt at fixing this, but I'm not sure it is the
right fix, hence it RFC status.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 kernel/irq/manage.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index a4afe5c..24e5eef 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1212,8 +1212,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		 * set the trigger type must match. Also all must
 		 * agree on ONESHOT.
 		 */
+		unsigned int old_msk = old->flags & IRQF_TRIGGER_MASK;
+
+		if (!old_msk)
+			old_msk = irqd_get_trigger_type(&desc->irq_data);
+
 		if (!((old->flags & new->flags) & IRQF_SHARED) ||
-		    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
+		    ((old_msk ^ new->flags) & IRQF_TRIGGER_MASK) ||
 		    ((old->flags ^ new->flags) & IRQF_ONESHOT))
 			goto mismatch;
 
-- 
2.9.3

Re: [RFC] Fix shared irq trigger-flags conflict when old irqaction uses IRQF_TRIGGER_NONE

[Marc Zyngier]

Hi Hans,

On 09/04/17 20:59, Hans de Goede wrote:
> While writing a driver for the INT0002 ACPI device found on Intel
> Bay and Cherry Trail devices I hit the following error:
> 
> "genirq: Flags mismatch irq 9. 00000084 (INT0002) vs. 00000080 (acpi)"
> 
> This is caused by drivers/acpi/osl.c first doing:
> 
> request_irq(irq, acpi_irq, IRQF_SHARED, "acpi", acpi_irq)
> 
> While the irqdata for the irq contains no trigger flags, resulting
> in an irqaction with IRQF_TRIGGER_NONE.
> 
> And then the INT0002 driver I'm working on calling platform_get_irq
> which does: irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
> 
> And then request_irq(irq, ..., IRQF_SHARED, ...) on the irq returned
> by platform_get_irq causes the error quoted above.
> 
> Arguably the genirq code should not hit the shared irq trigger-flags
> mismatch code if the old irqaction has IRQF_TRIGGER_NONE as flags.
> 
> This patch is an attempt at fixing this, but I'm not sure it is the
> right fix, hence it RFC status.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  kernel/irq/manage.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index a4afe5c..24e5eef 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1212,8 +1212,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>  		 * set the trigger type must match. Also all must
>  		 * agree on ONESHOT.
>  		 */
> +		unsigned int old_msk = old->flags & IRQF_TRIGGER_MASK;
> +
> +		if (!old_msk)
> +			old_msk = irqd_get_trigger_type(&desc->irq_data);
> +
>  		if (!((old->flags & new->flags) & IRQF_SHARED) ||
> -		    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
> +		    ((old_msk ^ new->flags) & IRQF_TRIGGER_MASK) ||
>  		    ((old->flags ^ new->flags) & IRQF_ONESHOT))
>  			goto mismatch;
>  
> 

I'm afraid you're just papering over the issue here, as you leave the
"old" descriptor in an inconsistent state w.r.t. the "new" descriptor.

My view is that the old irq_desc should be "upgraded" to the new trigger
configuration, because they are sharing a line and must have compatible
behaviours. NONE is effectively a wildcard, and the second interrupt
request should turn this wildcard into the real thing.

The opposite case also exists (request a LEVEL interrupt first, then a
NONE), and should be resolved the same way (NONE becomes LEVEL).

Thoughts?

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [RFC] Fix shared irq trigger-flags conflict when old irqaction uses IRQF_TRIGGER_NONE

[Hans de Goede]

HI,

On 10-04-17 12:13, Marc Zyngier wrote:
> Hi Hans,
>
> On 09/04/17 20:59, Hans de Goede wrote:
>> While writing a driver for the INT0002 ACPI device found on Intel
>> Bay and Cherry Trail devices I hit the following error:
>>
>> "genirq: Flags mismatch irq 9. 00000084 (INT0002) vs. 00000080 (acpi)"
>>
>> This is caused by drivers/acpi/osl.c first doing:
>>
>> request_irq(irq, acpi_irq, IRQF_SHARED, "acpi", acpi_irq)
>>
>> While the irqdata for the irq contains no trigger flags, resulting
>> in an irqaction with IRQF_TRIGGER_NONE.
>>
>> And then the INT0002 driver I'm working on calling platform_get_irq
>> which does: irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
>>
>> And then request_irq(irq, ..., IRQF_SHARED, ...) on the irq returned
>> by platform_get_irq causes the error quoted above.
>>
>> Arguably the genirq code should not hit the shared irq trigger-flags
>> mismatch code if the old irqaction has IRQF_TRIGGER_NONE as flags.
>>
>> This patch is an attempt at fixing this, but I'm not sure it is the
>> right fix, hence it RFC status.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  kernel/irq/manage.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
>> index a4afe5c..24e5eef 100644
>> --- a/kernel/irq/manage.c
>> +++ b/kernel/irq/manage.c
>> @@ -1212,8 +1212,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>>  		 * set the trigger type must match. Also all must
>>  		 * agree on ONESHOT.
>>  		 */
>> +		unsigned int old_msk = old->flags & IRQF_TRIGGER_MASK;
>> +
>> +		if (!old_msk)
>> +			old_msk = irqd_get_trigger_type(&desc->irq_data);
>> +
>>  		if (!((old->flags & new->flags) & IRQF_SHARED) ||
>> -		    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
>> +		    ((old_msk ^ new->flags) & IRQF_TRIGGER_MASK) ||
>>  		    ((old->flags ^ new->flags) & IRQF_ONESHOT))
>>  			goto mismatch;
>>
>>
>
> I'm afraid you're just papering over the issue here, as you leave the
> "old" descriptor in an inconsistent state w.r.t. the "new" descriptor.
>
> My view is that the old irq_desc should be "upgraded" to the new trigger
> configuration, because they are sharing a line and must have compatible
> behaviours.

There is no old irq_desc only an old ircaction, but yes that can easily
be updated to reflect the mask from the irq_data, or maybe we should not use
the oldaction for the trigger_mask bits at all and instead use
the trigger_mask from the irq_data as done in:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/kernel/irq/manage.c?id=7ee7e87dfb158e79019ea1d5ea1b0e6f2bc93ee4

For a different code path ? Thomas?

> NONE is effectively a wildcard, and the second interrupt
> request should turn this wildcard into the real thing.
 >
> The opposite case also exists (request a LEVEL interrupt first, then a
> NONE), and should be resolved the same way (NONE becomes LEVEL).

The 2nd order of requesting irqs will already work because of:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/kernel/irq/manage.c?id=4b357daed698c95d6b5eacc1c3c4afa206071ba2

Where the new_action trigger_mask gets filled with the triger_mask
from the irq_data, which is a further hint that looking at
irqd_get_trigger_type(&desc->irq_data) rather then at
(old->flags IRQF_TRIGGER_MASK) is probably the right fix.

Note btw that 4b357daed698 is (part of) what is breaking things for
my use-case, I request the irq with IRQF_TRIGGER_NONE but
4b357daed698 modifies that before comparing the new trigger flags
to the old.

Regards,

Hans

Re: [RFC] Fix shared irq trigger-flags conflict when old irqaction uses IRQF_TRIGGER_NONE

[Thomas Gleixner]

On Mon, 10 Apr 2017, Hans de Goede wrote:
> Where the new_action trigger_mask gets filled with the triger_mask
> from the irq_data, which is a further hint that looking at
> irqd_get_trigger_type(&desc->irq_data) rather then at
> (old->flags IRQF_TRIGGER_MASK) is probably the right fix.
> 
> Note btw that 4b357daed698 is (part of) what is breaking things for
> my use-case, I request the irq with IRQF_TRIGGER_NONE but
> 4b357daed698 modifies that before comparing the new trigger flags
> to the old.

The issue here is, that at the time of the first setup_irq() the trigger
type in irq_data is NONE. As a consequence the following is a NOOP:

     if (!new->trigger)
	new->flags |= get_type(irqdata);

Now the irq is started up for the first time and then the actual trigger
type gets established, but that's to late to fix up new->flags.

So yes, we should change the logic for the shared case to:

   if (old) {
      	    oldtype = get_type(irqdata);

	    if (oldtype != newtype)
	       	    goto mismatch;

That should cover all cases.

Thanks,

	tglx