Subject: [PATCH 10/20] of/irq: fix interrupt parent lookup procedure

From: [email-masked] (Grant Likely)
Date: Tue, 15 May 2012 12:41:49 -0600

On Tue, 15 May 2012 17:29:14 +0900, Kukjin Kim <[email-masked]> wrote:
> Thomas Abraham wrote:
> > 
> > The interrupt parent lookup fails for a node that is a interrupt-controller
> > but does not have an explict interrupt-parent property and instead inherits
> > this property from the root node.
> > 
> > Consider the nodes listed below.
> > 
> >     / {
> >         interrupt-parent = <&intc_level1>;
> > 
> >         intc_level1: interrupt-controller at xxx {
> >                 interrupt-controller;
> >                 #interrupt-cells = <3>;
> >                 <rest of the properties here>;
> >         };
> > 
> >         intc_level2: interrupt-controller at yyy {
> >                 interrupt-controller;
> >                 #interrupt-cells = <2>;
> >                 <rest of the properties here>;
> >         };
> >     };
> > 
> > The interrupt parent lookup for interrupt-controller at yyy fails. It inherits
> > the interrupt-parent property from the root node and the root node ('/')
> > specifies a 'interrupt-parent' property which represents the default interrupt
> > root controller. But, the property '#interrupt-cells' might not be specified
> > in the root node.
> > 
> > In case a interrupt controller node does not include a 'interrupt-parent'
> > property but inherits that property from the root node, the check for
> > 'interrupt-cells' property in the root node fails. Fix this removing the
> > check for 'interrupt-cells' property.

Hmmm... I dont see the bug...  From your description above, I see the
following sequence.

First iteration:
	child = &ic at yyy;
	cannot find "interrupt-parent" so take 'if' clause
		p = of_get_parent(child);  (root)
	iteration continues because #interrupt-cells not found in 'p'(root)
Second iteration:
	child = root;
	found "interrupt-parent", so take 'else' clause
		p = of_find_node_by_phandle();  (ic at xxx)
	iteration stops because #interrupt-cells is found in 'p'(ic at xxx)

What am I missing in my admittedly short look at the code?

g.

> > 
> > Signed-off-by: Thomas Abraham <[email-masked]>
> > ---
> >  drivers/of/irq.c |    4 +++-
> >  1 files changed, 3 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> > index 9cf0060..a520363 100644
> > --- a/drivers/of/irq.c
> > +++ b/drivers/of/irq.c
> > @@ -66,14 +66,16 @@ struct device_node *of_irq_find_parent(struct device_node *child)
> >  		if (parp == NULL)
> >  			p = of_get_parent(child);
> >  		else {
> > +			of_node_put(child);
> >  			if (of_irq_workarounds & OF_IMAP_NO_PHANDLE)
> >  				p = of_node_get(of_irq_dflt_pic);
> >  			else
> >  				p = of_find_node_by_phandle(be32_to_cpup(parp));
> > +			return p;
> >  		}
> >  		of_node_put(child);
> >  		child = p;
> > -	} while (p && of_get_property(p, "#interrupt-cells", NULL) == NULL);
> > +	} while (p);

This does break one use-case.  Sometimes the interrupt-parent is the
same node when an 
> > 
> >  	return p;
> >  }
> > --
> > 1.7.5.4
> 
> Hi Grant and Rob,
> 
> I'm ok on this and this patch and #11 patch in this series are required for patches that add device tree based support for wakeup
> interrupts on EXYNOS5250.
> 
> So could you have a look at this patch and let us know if this is okay or any rework is required.
> 
> Thanks.
> 
> Best regards,
> Kgene.
> --
> Kukjin Kim <[email-masked]>, Senior Engineer,
> SW Solution Development Team, Samsung Electronics Co., Ltd.
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.