Re: [PATCH 0/2] sparc32,leon: PCI patches

[Daniel Hellstrom <daniel@gaisler.com>]

David Miller wrote:

>From: Daniel Hellstrom <daniel@gaisler.com>
>Date: Fri, 20 May 2011 10:01:11 +0200
>
>  
>
>>David Miller wrote:
>>
>>    
>>
>>>From: Daniel Hellstrom <daniel@gaisler.com>
>>>Date: Thu, 19 May 2011 15:13:14 +0200
>>>
>>> 
>>>      
>>>
>>>>The PowerPC for example assign resources
>>>>(arch/powerpc/kernel/pci-common.c), and PowerPC may also have a
>>>>OpenBoot loader:
>>>>   
>>>>        
>>>>
>>>On some powerpc systems, like sparc64 Niagara, you can't blindly go
>>>poking around the PCI config space at all and must rely completely
>>>and entirely upon the OpenBoot device tree.
>>> 
>>>      
>>>
>>I see, that may be because IRQ routing or resource allocation is done
>>in a non-standard way I guess, perhaps because of bugs on some of the
>>motherboards.
>>    
>>
>
>Or because PCI accesses have to go through a hypervisor.
>  
>
Aaah. Its a pity sparc32 doesn't have a hypervisor, we could do really 
cool stuff with that.

>The point is that having it all setup in OpenBoot is a great
>abstraction because you don't have to care.
>
>It also allows things like being able to disable devices with things
>like "pcia-probe-list" and "pcib-probe-list" properties in the PCI
>host controller node, which we end up honoring on sparc64 simply
>because we never directly probe PCI space to probe devices.
>  
>
I agree that it is a better solution in that case and in other cases 
too. The problem will be for me to write a PCI Library in the limited 
context of the PROM, it is much more complex that writing a PCI host 
driver. The non-free PCI specification alone is heavy, compatibility 
between PCI revisions and then there is the bridge specification... ugg, 
I will probably have to leave that to the next generation :)

Daniel