RE: [RFC] powerpc/fsl-pci: Document the "fsl,has-isa" property for Freescale PCI

-----Original Message-----
From: linuxppc-dev-bounces+b38951=freescale.com-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
[mailto:linuxppc-dev-bounces+b38951=freescale.com-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org] On
Behalf Of Jia Hongtao-B38951
Sent: Friday, April 06, 2012 11:05 AM
To: Kumar Gala
Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org;
Li Yang-R58472
Subject: RE: [RFC] powerpc/fsl-pci: Document the "fsl,has-isa" property
for Freescale PCI

quoted

-----Original Message-----
From: Kumar Gala [mailto:galak-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org]
Sent: Wednesday, April 04, 2012 9:09 PM
To: Jia Hongtao-B38951
Cc: linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; Li Yang-R58472; devicetree-
discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
Subject: Re: [RFC] powerpc/fsl-pci: Document the "fsl,has-isa" property
for Freescale PCI


On Apr 1, 2012, at 1:56 AM, Jia Hongtao wrote:

quoted

If PCI is primary bus we should set isa_io/mem_base when parsing PCI

bridge

quoted

resources from device tree. The previous way to check the primary bus

based

quoted

on a hard-coded address named primary_phb_addr. Now we add a property

named

quoted

"fsl,has-isa" into device tree. In kernel we use this property to

find

quoted

out

quoted

the bus is primary or not. This way is more flexible.

Signed-off-by: Jia Hongtao <redacted>
Signed-off-by: Li Yang <redacted>
---
.../devicetree/bindings/powerpc/fsl/pci.txt        |   36

++++++++++++++++++++

quoted

1 files changed, 36 insertions(+), 0 deletions(-)
create mode 100644

Documentation/devicetree/bindings/powerpc/fsl/pci.txt

This isn't freescale specific, its linux specific.  If anything the
property should be linux,has-isa.

But in general I dont think this is a good idea.  In truth one could
search the device tree for:

	device_type = "isa";

to try and set this dynamically.

- k

Yes, it's not Freescale specific, but it's only used by Freescale now in
the kernel. This is why I named the property as "fsl,has-isa".

To indicate PCI bus is primary we have three ways to go and we now like
the 2nd solution:

1. As this patch said, we add a property to device tree manually.

2. Set this property dynamically in uboot when scanning PCI bridge.
Actually we have already done this. The problem is users should update
uboot and kernel together or it's not work. To support old uboot we
decide
to add this property into device tree too temporarily. We will remove it
from device tree at an appropriate future.

3. Just as you said we could search the device tree by device_type =
"isa".
   There are two problems here:
	* There is no OF API for searching just in PCI node now. That means
	  we can't easily find whether there is "isa" bridge or not under
	  this PCI controller while scanning it.
	* Boards MPC8541CDS and MPC8555CDS has no "isa" node in device tree
	  but has ISA bridge under PCI controller.

- Jia Hongtao

Hi Kumar,

I agree with the name change from "fsl,has-isa" to "linux,has-isa".
If this is ok I will update this patch and send the patches based on this
new property.

Also, I have a question about "isa" node in dts. Is this node being used
by kernel? If not we can remove it from all boards and check the primary
bus by uboot. If "isa" is useful why MPC8541CDS and MPC8555CDS has no
"isa" node in device tree but has ISA bridge under PCI controller?

Thanks.
- Jia Hongtao