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

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Message-ID: <20150220154038.GE18111@kroah.com>
Date:	Fri, 20 Feb 2015 07:40:38 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] drivers: platform: parse IRQ flags from resources

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...
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