Bjorn,
On 06/02/2015 12:58 PM, Bjorn Helgaas wrote:
On Tue, Jun 2, 2015 at 12:02 PM, Guenter Roeck <[email protected]> wrote:
[ ... ]
I wonder if we can do the same with pci_read_bridge_mmio_pref(), and
somehow get rid of pci_bridge_check_ranges() altogether?
I think I looked at doing that a while back, and it seems like there was
some wrinkle, but I don't remember what it was.
After looking into this some more, I think the wrinkle may be that
pci_read_bridge_bases() and thus pci_read_bridge_io() isn't called
on probe-only systems (if PCI_PROBE_ONLY is set). A secondary
problem is that pci_read_bridge_io() does not enable a resource
if it is explicitly disabled (base > limit), but the subsequent call
to pci_bridge_check_ranges() unconditionally enables it.
I haven't researched this, but it sounds wrong that we skip
pci_read_bridge_bases() if PCI_PROBE_ONLY is set. I think
PCI_PROBE_ONLY should mean "look, but don't touch." So I think we
should always look at the bridge windows, and my advice is to see if
it looks reasonable to change this aspect of PCI_PROBE_ONLY.
Looks like Lorenzo's patch is going to take care of that problem.
How about the second problem mentioned above ? One option might be to
keep pci_bridge_check_ranges() but only use it to _enable_ the various
ranges (and maybe rename it accordingly) ?
Thanks,
Guenter
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