[PATCH] PCI: add MSI INTX_DISABLE quirks for AR8161/AR8162/AR8171/AR8172

[Huang, Xiong]

> > Wei, thanks for you feedback, this patch is just follow the function
> > 'quirk_msi_intx_disable_ati_bug' in quirks.c Is it ok if I revise code as:
> >         static void quirk_msi_intx_disable_qca_bug(struct pci_dev *dev)
> >         {
> >                 If (dev->revision < 0x18)
> >                         dev->dev_flags |=  PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG;
> >         }
> 
> Per the comment in pci_ids.h, you should not add #defines there unless they
> are used in more than one place.  So in this case, you would just use the hex
> constants directly in quirks.c, as we already do for the existing ATTANSIC
> quirks.
> 
> As far as the loop with pci_get_device(), the revised patch is probably what
> you want, but it is not functionally equivalent to the original.  Let's say you
> have two devices:
> 
>   1) 8161 rev 0x18
>   2) 8171 rev 0x17
> 
> The original patch will disable MSI for the 8161 because there is
> *another* device (the 8171) with rev < 0x18.  I doubt that's what you want.
> 
> I'd like to see a dev_info() saying that you're disabling MSI for this device so
> that when somebody complains "my device should be using MSI but isn't,"
> it's easy to figure out why not.
> 

Bjorn, your example is very clear for me. I made a bug for the original patch :)

BTW. The flag of PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG isn't disable MSI on such devices,
But not enable PCI INT_DISABLE bit for PCI_COMMAND register when enable MSI function.
Some devices like AR8161 with revision lower than 0x18 will not issue MSI interrupt if INT_DISABLE bit is set.

Thanks
Xiong