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List:       linux-pci
Subject:    Re: [PATCH v8 00/61] PCI: Resource allocation cleanup for v4.4
From:       Benjamin Herrenschmidt <benh () kernel ! crashing ! org>
Date:       2015-10-31 20:47:04
Message-ID: 1446324424.4060.1.camel () kernel ! crashing ! org
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On Sat, 2015-10-31 at 14:51 -0400, David Miller wrote:
> This is the way OF seems to work.
> 
> It maps all of the ROMs essentially to the same address range, but
> only enables one at a time as it inspects the ROMs and builds the
> device tree during power-on.
> 
> Then it makes sure all of them are disabled, and can therefore use
> some of that address range for mapping other BARs.
> 
> So if ROMs are disabled, you cannot put the address of such ROMs BAR
> in the kernel's assigned PCI address resource list.
> 
> I hope that is what you are doing?

I've seen that sort of stuff on x86 as well. Possibly on POWER, I don't
remember for sure.

I've also seen the VBIOS  of some cards manually remap the ROM BAR to
cover BAR 0, extract stuff from it, then disable it.

I think the ROM BAR must be treated as "special". It should probably
done in a separate pass from all the other BARs of all the other
adapters to be honest, and remapped if there's any conflict.

Cheers,
Ben

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