[PATCH 3/6] powerpc/fsl-pci: Determine primary bus by looking for ISA node

[Jia Hongtao-B38951]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Wednesday, July 25, 2012 2:48 AM
> To: Jia Hongtao-B38951
> Cc: linuxppc-dev at lists.ozlabs.org; galak at kernel.crashing.org; Wood Scott-
> B07421; Li Yang-R58472
> Subject: Re: [PATCH 3/6] powerpc/fsl-pci: Determine primary bus by
> looking for ISA node
> 
> On 07/24/2012 05:20 AM, Jia Hongtao wrote:
> > PCI host bridge is primary bus if it contains an ISA node. But not all
> boards
> > fit this rule. Device tree should be updated for all these boards.
> >
> > Signed-off-by: Jia Hongtao <B38951 at freescale.com>
> > Signed-off-by: Li Yang <leoli at freescale.com>
> > ---
> >  arch/powerpc/include/asm/pci-bridge.h |    1 +
> >  arch/powerpc/sysdev/fsl_pci.c         |   31 ++++++++++++++++++++++++-
> ------
> >  arch/powerpc/sysdev/fsl_pci.h         |   12 +++++++++++-
> >  3 files changed, 36 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/pci-bridge.h
> b/arch/powerpc/include/asm/pci-bridge.h
> > index ac39e6a..b48fa7f 100644
> > --- a/arch/powerpc/include/asm/pci-bridge.h
> > +++ b/arch/powerpc/include/asm/pci-bridge.h
> > @@ -20,6 +20,7 @@ struct device_node;
> >  struct pci_controller {
> >  	struct pci_bus *bus;
> >  	char is_dynamic;
> > +	int is_primary;
> >  #ifdef CONFIG_PPC64
> >  	int node;
> >  #endif
> > diff --git a/arch/powerpc/sysdev/fsl_pci.c
> b/arch/powerpc/sysdev/fsl_pci.c
> > index 99a3e78..2a369be 100644
> > --- a/arch/powerpc/sysdev/fsl_pci.c
> > +++ b/arch/powerpc/sysdev/fsl_pci.c
> > @@ -453,6 +453,7 @@ int __init fsl_add_bridge(struct device_node *dev,
> int is_primary)
> >
> >  	hose->first_busno = bus_range ? bus_range[0] : 0x0;
> >  	hose->last_busno = bus_range ? bus_range[1] : 0xff;
> > +	hose->is_primary = is_primary;
> >
> >  	setup_indirect_pci(hose, rsrc.start, rsrc.start + 0x4,
> >  		PPC_INDIRECT_TYPE_BIG_ENDIAN);
> > @@ -932,18 +933,34 @@ void pci_check_swiotlb(void)
> >  }
> >  #endif
> >
> > -int primary_phb_addr;
> > +/*
> > + * Recursively scan all the children nodes of parent and find out if
> there
> > + * is "isa" node. Return 1 if parent has isa node otherwise return 0.
> > + */
> > +int has_isa_node(struct device_node *parent)
> > +{
> > +	static int result;
> > +	struct device_node *cur_child;
> > +
> > +	cur_child = NULL;
> > +	result = 0;
> > +	while (!result && (cur_child = of_get_next_child(parent,
> cur_child))) {
> > +		/* Get "isa" node and return 1 */
> > +		if (of_node_cmp(cur_child->type, "isa") == 0)
> > +			return result = 1;
> > +		has_isa_node(cur_child);
> > +	}
> > +
> > +	return result;
> > +}
> 
> Why are you reimplementing this?  It's already in Linus's tree.  See
> fsl_pci_init().
> 
> Plus, your version is recursive which is unacceptable in kernel code
> with a small stack (outside of a few rare examples where the depth has a
> small fixed upper bound), and once it finds an ISA node, it returns 1
> forever, regardless of what node you pass in in the future.
> 
> -Scott

About recursion I will do some more investigation.
If it finds ISA it returns 1. But for next PCI node it will return 0 if
no ISA is found (note that I set result to 0 at the beginning).

-Hongtao.