[PATCH v3 3/3] PCI: ARM: add support for generic PCI host controller

On Tue, Feb 18, 2014 at 08:19:21PM +0000, Arnd Bergmann wrote:

On Tuesday 18 February 2014 19:57:32 Will Deacon wrote:

quoted

On Tue, Feb 18, 2014 at 07:36:54PM +0000, Will Deacon wrote:

quoted

On Tue, Feb 18, 2014 at 07:32:33PM +0000, Arnd Bergmann wrote:

quoted

On Tuesday 18 February 2014 19:09:29 Will Deacon wrote:
Regarding the PCI_PROBE_ONLY flag, how do you set that? Should we
have a standard DT property for that? On PowerPC we already specified
"linux,pci-probe-only" and "linux,pci-assign-all-buses", which seems
reasonable to use in architecture independent code as well.

For arch/arm/ it's done on the command line (pci=firmware) but yes, for the
generic driver it sounds like a good idea to put this in the device-tree.
I'll look at adding the ppc properties in the next version.

Damn, I spoke too soon. PowerPC puts this information in the /chosen node, so
it applies to all PCI host controllers in the system. That then maps nicely
to pci_{add,clear}_flags which are global properties in Linux.

It sounds like this should really be per-controller. What do you think?

I don't have a strong opinion either way. I think the reason for having it
in the /chosen node is so that a second-stage boot loader can easily
override it, which is not a concern for us. In particular, the properties
are only used on rtas-pci, which means we access the config space to
firmware runtime abstraction services rather than hardware registers.

Apparently the embedded powerpc platforms don't support these flags at
all, which I also didn't notice at first.

Even in the rtas case there's a:

	#ifdef CONFIG_PPC32 /* Will be made generic soon */

for linux,pci-assign-all-buses. I think I'll just go for
linux,pci-probe-only initially, especially as PCI_REASSIGN_ALL_BUS isn't
actually used anywhere outside of arch/powerpc/.

Will