Re: [BISECTED] Regression: Solidrun Clearfog Base won't boot since "PCI: mvebu: Only remap I/O space if configured"

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Wed, Sep 12, 2018 at 09:49:41PM +0300, Baruch Siach wrote:
> I reproduced the same Oops on Clearfog Base without any taint:
> 
> [    1.476401] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
...
> [    1.855954] Code: e2844004 e5972000 e3520000 0affffee (e7f001f2)

That is a BUG().  Please turn on verbose bug reporting to get more
information about the cause.

There are two possibilities:

        BUG_ON(addr >= end);

and

                BUG_ON(!pte_none(*pte));

It's probably the latter - the region is probably already mapped, that
being the PCI IO region.

The original driver was setup to call pci_ioremap_io() as the very
last thing - and as the driver is non-removable, we were guaranteed
to never tear down this mapping (which is sensible, it's published
to userspace.)

However, the current code calls pci_ioremap_io() much earlier, in
a path where probe failures can occur.  This breaks pci_ioremap_io()'s
requirements - it must not be called more than once.  So:

ee1604381a37 ("PCI: mvebu: Only remap I/O space if configured")

is basically incorrect - pci_ioremap_io() needs to move back to a
place where it is only called in a path which will never fail.
However, looking at the generic host bits, I'm not sure such a place
exists in the new effort to make stuff more generic.

-- 
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