linux-kernel - Re: [PATCH] drivers: platform: parse IRQ flags from resources

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Date:	Thu, 05 Mar 2015 14:07:39 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] drivers: platform: parse IRQ flags from resources

Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:

> On Wed, Feb 18, 2015 at 05:12:18PM +0100, Linus Walleij wrote:
>> This fixes a regression from the net subsystem:
>> After commit d52fdbb735c36a209f36a628d40ca9185b349ba7
>> "smc91x: retrieve IRQ and trigger flags in a modern way"
>> a regression would appear on some legacy platforms such
>> as the ARM PXA Zylonite that specify IRQ resources like
>> this:
>> 
>> static struct resource r = {
>>        .start  = X,
>>        .end    = X,
>>        .flags  = IORESOURCE_IRQ | IORESOURCE_IRQ_HIGHEDGE,
>> };
>> 
>> The previous code would retrieve the resource and parse
>> the high edge setting in the SMC91x driver, a use pattern
>> that means every driver specifying an IRQ flag from a
>> static resource need to parse resource flags and apply
>> them at runtime.
>> 
>> As we switched the code to use IRQ descriptors to retrieve
>> the the trigger type like this:
>> 
>>   irqd_get_trigger_type(irq_get_irq_data(...));
>> 
>> the code would work for new platforms using e.g. device
>> tree as the backing irq descriptor would have its flags
>> properly set, whereas this kind of oldstyle static
>> resources at no point assign the trigger flags to the
>> corresponding IRQ descriptor.
>> 
>> To make the behaviour identical on modern device tree
>> and legacy static platform data platforms, modify
>> platform_get_irq() to assign the trigger flags to the
>> irq descriptor when a client looks up an IRQ from static
>> resources.
>> 
>> Fixes: d52fdbb735c3 ("smc91x: retrieve IRQ and trigger flags in a modern way")
>> Tested-by: Robert Jarzmik <robert.jarzmik@...e.fr>
>> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>> ---
>> Greg/Grant: I'm a bit uncertain here. It's kind of
>> unintuitive that the platform_get_irq() function go around
>> setting trigger flags on IRQ descriptors, but it is *also*
>> unintuitive that the descriptor has all the right flags
>> from a device tree but not from an identical static
>> resource. And it is bloated to have resource parsing in
>> each and every driver. The alternative is to revert
>> the offending patch and live with some resource parsing
>> all over the place. (Such a patch is posted.)
>> ---
>>  drivers/base/platform.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>> 
>> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
>> index 9421fed40905..e68ab79df28b 100644
>> --- a/drivers/base/platform.c
>> +++ b/drivers/base/platform.c
>> @@ -101,6 +101,15 @@ int platform_get_irq(struct platform_device *dev, unsigned int num)
>>  	}
>>  
>>  	r = platform_get_resource(dev, IORESOURCE_IRQ, num);
>> +	/*
>> +	 * The resources may pass trigger flags to the irqs that need
>> +	 * to be set up. It so happens that the trigger flags for
>> +	 * IORESOURCE_BITS correspond 1-to-1 to the IRQF_TRIGGER*
>> +	 * settings.
>> +	 */
>> +	if (r && r->flags & IORESOURCE_BITS)
>> +		irqd_set_trigger_type(irq_get_irq_data(r->start),
>> +				      r->flags & IORESOURCE_BITS);
>
> Ah, found this now.
>
> I'll defer to Grant as to what to do here, as I have no idea...

Hi Grant,

Any comment on the patch ?

Cheers.

-- 
Robert
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