linux-kernel - Re: [PATCH] Revert "smc91x: retrieve IRQ and trigger flags in a modern way"

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Date:	Fri, 13 Feb 2015 10:16:09 +0800
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:	Nicolas Pitre <nico@...xnic.net>,
	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "smc91x: retrieve IRQ and trigger flags in a
 modern way"

On Fri, Feb 13, 2015 at 12:59 AM, Robert Jarzmik <robert.jarzmik@...e.fr> wrote:

> The commit breaks the legacy platforms, ie. these not using device-tree,
> and setting up the interrupt resources with a flag to activate edge
> detection. The issue was found on the zylonite platform.
>
> The reason is that zylonite uses platform resources to pass the interrupt number
> and the irq flags (here IORESOURCE_IRQ_HIGHEDGE). It expects the driver to
> request the irq with these flags, which in turn setups the irq as high edge
> triggered.
>
> After the patch, this was supposed to be taken care of with :
>   irq_resflags = irqd_get_trigger_type(irq_get_irq_data(ndev->irq));
>
> But irq_resflags is 0 for legacy platforms, while for example in
> arch/arm/mach-pxa/zylonite.c, in struct resource smc91x_resources[] the
> irq flag is specified. This breaks zylonite because the interrupt is not
> setup as triggered, and hardware doesn't provide interrupts.
>
> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>

But isn't the real problem that in the device tree case,
irq_get_irq_data(ndev->irq) will work becaus parsing an interrupt
from the device tree populates it correctly in platform_get_irq()
whereas for the legacy lookup it just fetches the number.

So to me it seems like a weakness in the platform_get_irq()
helper altogether.

Does the following work? (I can send as a separate patch for
testing if you like).

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 9421fed40905..301f4b9ae908 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->flags & IORESOURCE_BITS)
+        irqd_set_trigger_type(irq_get_irq_data(r->start),
+                      r->flags & IORESOURCE_BITS);


Yours,
Linus Walleij
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