Re: [PATCH v2] PCI: Fix Intel i210 by avoiding overlapping of BARs

[Michael Walle]

Hi Bjorn,

Am 2021-01-17 20:27, schrieb Michael Walle:
> Am 2021-01-16 00:57, schrieb Bjorn Helgaas:
> > On Wed, Jan 13, 2021 at 12:32:32AM +0100, Michael Walle wrote:
> > > Am 2021-01-12 23:58, schrieb Bjorn Helgaas:
> > > > On Sat, Jan 09, 2021 at 07:31:46PM +0100, Michael Walle wrote:
> > > > > Am 2021-01-08 22:20, schrieb Bjorn Helgaas:
> >
> > > > > > 3) If the Intel i210 is defective in how it handles an Expansion ROM
> > > > > > that overlaps another BAR, a quirk might be the right fix. But my
> > > > > > guess is the device is working correctly per spec and there's
> > > > > > something wrong in how firmware/Linux is assigning things.  That would
> > > > > > mean we need a more generic fix that's not a quirk and not tied to the
> > > > > > Intel i210.
> > > > >
> > > > > Agreed, but as you already stated (and I've also found that in
> > > > > the PCI spec) the Expansion ROM address decoder can be shared by
> > > > > the other BARs and it shouldn't matter as long as the ExpROM BAR
> > > > > is disabled, which is the case here.
> > > >
> > > > My point is just that if this could theoretically affect devices
> > > > other than the i210, the fix should not be an i210-specific quirk.
> > > > I'll assume this is a general problem and wait for a generic PCI
> > > > core solution unless it's i210-specific.
> > >
> > > I guess the culprit here is that linux skips the programming of the
> > > BAR because of some broken Matrox card. That should have been a
> > > quirk instead, right? But I don't know if we want to change that, do
> > > we? How many other cards depend on that?
> >
> > Oh, right.  There's definitely some complicated history there that
> > makes me a little scared to change things.  But it's also unfortunate
> > if we have to pile quirks on top of quirks.
> >
> > > And still, how do we find out that the i210 is behaving correctly?
> > > In my opinion it is clearly not. You can change the ExpROM BAR value
> > > during runtime and it will start working (while keeping it
> > > disabled).  Am I missing something here?
> >
> > I agree; if the ROM BAR is disabled, I don't think it should matter at
> > all what it contains, so this does look like an i210 defect.
> >
> > Would you mind trying the patch below?  It should update the ROM BAR
> > value even when it is disabled.  With the current pci_enable_rom()
> > code that doesn't rely on the value read from the BAR, I *think* this
> > should be safe even on the Matrox and similar devices.
>
> Your patch will fix my issue:
>
> Tested-by: Michael Walle <michael@xxxxxxxx>

any news on this?

-michael