Re: Ignore disabled ROM resources at setup

[Jon Smirl <jonsmirl@gmail.com>]

On 8/30/05, Linus Torvalds <torvalds@osdl.org> wrote:
> 
> 
> On Mon, 29 Aug 2005, David S. Miller wrote:
> >
> > So I think the kernel, by not enabling the ROM, is doing the
> > right thing here.
> 
> Notice that on ppc even older versions didn't actually _enable_ the rom,
> but they would write the non-enabled address to the PCI_ROM_ADDRESS
> register, so that anybody who read that register would see _where_ the ROM
> would be enabled if it was enabled.
> 
> That's the thing that changed in the commit Ben dislikes. Now, if the ROM
> is disabled, we won't even write the disabled address to the PCI register,
> because it led to trouble on some strange Matrox card. Probably a card
> that nobody has ever used on PPC, and certainly not on a Powerbook, so in
> that sense the apparent breakage on ppc is arguably "unnecessary" as far
> as Ben is concerned.
> 
> But I notice the problem: pci_enable_rom() is indeed broken with the
> change.
> 
> Ben, does this (totally untested) patch fix it for you?
> 
>                         Linus
> 
> ----
> diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
> --- a/drivers/pci/rom.c
> +++ b/drivers/pci/rom.c
> @@ -23,11 +23,14 @@
>   */
>  static void pci_enable_rom(struct pci_dev *pdev)
>  {
> -       u32 rom_addr;
> +       struct resource *res = pdev->resource + PCI_ROM_RESOURCE;
> +       struct pci_bus_region region;
> 
> -       pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
> -       rom_addr |= PCI_ROM_ADDRESS_ENABLE;
> -       pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
> +       if (!res->flags)
> +               return;
> +
> +       pcibios_resource_to_bus(pdev, &region, res);
> +       pci_write_config_dword(pdev, pdev->rom_base_reg, region.start | PCI_ROM_ADDRESS_ENABLE);
>  }

I was reading the status out of the PCI config space to account for
our friend X which enables ROMs without informing the OS. With X
around PCI config space can get out of sync with the kernel
structures.


> 
>  /**
> -
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-- 
Jon Smirl
jonsmirl@gmail.com