On Fri, Dec 14, 2007 at 07:51:06AM +1100, Benjamin Herrenschmidt wrote:
> If the device is behind a P2P bridge and the BIOS has set the windows of
> that bridge so tightly that there is no room to allocate the MMIO BAR,
> then a full disable/full enable would fail on a device that would
> otherwise work using only PIO.
It won't be a problem with separate io/mmio enable.
> However, I'd be curious to see that happening in practice :-)
>
> But I think it's fair enough to do an IO only / MEM only approach. I've
> seen cases where IO is just not useable because of other constraints and
> so I expect the MEM-only case to be more common, especially on non-x86.
Everybody wants MEM if it's available - it's just faster :-)
So I guess a common case will be
if (pci_enable_device_mmio(dev)) {
/* failed, fallback to IO */
if (pci_enable_device_io(dev))
return -ENODEV;
...
}
Ivan.
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