Re: Ignore disabled ROM resources at setup

[Linus Torvalds]

On Tue, 30 Aug 2005, Benjamin Herrenschmidt wrote:
> 
> I was just testing a slightly different one that appear to fix the
> problem :
...
> +     rom_addr = region.start | (res->flags & PCI_REGION_FLAG_MASK);

I worry about this one. It's not really correct. The low en bits are 
"reserved", and while I don't know whether writing zero is always correct, 
I do know that just writing the low 4 bits with the old value is a bit 
strange. And the flags don't save the other bits.

So I'd prefer either my previous diff, or one that just re-reads the bits 
entirely, something like the appended..

What does the PCI spec say about the reserved bits? Do we have to save 
them?

                        Linus

---
diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
--- a/drivers/pci/rom.c
+++ b/drivers/pci/rom.c
@@ -24,9 +24,16 @@
 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;
 
+       if (!res->flags)
+               return;
+
+       pcibios_resource_to_bus(pdev, &region, res);
        pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
-       rom_addr |= PCI_ROM_ADDRESS_ENABLE;
+       rom_addr &= ~PCI_ROM_ADDRESS_MASK;
+       rom_addr |= region.start | PCI_ROM_ADDRESS_ENABLE;
        pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
 }
 
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