Re: xilinx-pci driver and pci in general

From: Michal Simek
Date: Fri Jan 15 2010 - 04:25:35 EST

Benjamin Herrenschmidt wrote:
On Wed, 2010-01-13 at 16:23 +0100, Michal Simek wrote:

The main problems are:
ppc use ppc_md struct which we don't have it on Microblaze.
xilinx-pci driver uses exclude_device function. This function is used in indirect_pci.c too. There could be a way to move that function directly to pci_controller structure which could be useful for other controllers too. What do you think?

Then there are some other ppc_md. calling like pcibios_after_init which
if I see correctly not used for ppc too.

We may not be using after_init() anymore in which case you are welcome
to send a patch to remove it :-)

hmm. I used older kernel and I see that in the latest version powermac
use it. :-( I will just remove it.

As for the others, well ... maybe you can do wrappers for these that
call into ppc_md. on powerpc and into some kind of arch_pci_ops. that
the platform provides on microblaze ?

I'm not sure moving them into the pci_controller is the best way to go

ok. I will remove that part of code for now.

The next thing is that some files contains asm/machdep.h which could be added to asm/pci-bridge.h and the same is for asm/ppc-pci.h

Yeah, moving includes like that is ok.

Files contains CONFIG_PPC_OF and we would like to use only CONFIG_OF.
I remember any discuss around but not sure what was the conclusion on powerpc.

I think that should be allright, Grant, any objection there ?

Part of headers are the same that's why there will be a space to move them to asm-generic.

If you can convince other archs that it makes sense to do so ? :-)

will try.

Anyway: I look at your dma-mapping.h and you can use asm-generic/dma-mapping-common.h as I am using.

Not just quite yet, there's still some stuff we need to cleanup with
the !coherent cases.

Then I have some question about EARLY_PCI_OP in ppc_32.c. Is there any reason to use early_##rw##_config_##size fucntions instead of proper pci_bus_##rw##_config_##size functions?
There is one comment that these functions are used before PCI scanning is done but there are used the same function as are in driver/pci/access.c.
Is there any "secret" reason to do it in this way?

Well, first of all, those aren't ppc32 only anymore, they are in
pci-common.c now. Then, if you look at them you'll notice that
they are just a wrapper on top of pci_bus_* which uses a fake
pci_bus structure. IE. They are meant to be used in very early
arch fixup code at a time when we may not even have the struct
pci_bus at hand. Their use is pretty rare though, maybe we -could-
get rid of them at some stage by moving some of that fixup code.

Thanks for that.

Thanks for this early discuss. I would like to hear your opinion and then I will choose solution how to add our pci support to mainline.

I will keep you informed but I see that I will add that part of code to mainline and then we look at consolidation work.



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Michal Simek, Ing. (M.Eng)
w: p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux -
Microblaze U-BOOT custodian

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