Re: [PATCH 1/2] eisa, PCI: Fix bus res reference

[Bjorn Helgaas]

On Wed, Mar 27, 2013 at 10:28 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> Matthem found that 3.8.3 is having problems with an old (ancient)
> PCI-to-EISA bridge, the Intel 82375. It worked with the 3.2 kernel.
> He identified the 82375, but doesn't assign the struct resource *res
> pointer inside the struct eisa_root_device, and panics.
>
> After looking at pci_eisa_init(), found it referring bus resource
> directly instead of pci_bus_resource_n().
>
> After commit 45ca9e97 (PCI: add helpers for building PCI bus resource lists)
> and commit 0efd5aab (PCI: add struct pci_host_bridge_window with CPU/bus
> address offset), bus->resource[] is not used for pci root bus any more.
>
> Fix it by using pci_bus_resource_n() and correct idx for root bus.
>
> Reported-by: Matthew Whitehead <mwhitehe@xxxxxxxxxx>
> Tested-by: Matthew Whitehead <mwhitehe@xxxxxxxxxx>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxx
>
> ---
>  drivers/eisa/pci_eisa.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/drivers/eisa/pci_eisa.c
> ===================================================================
> --- linux-2.6.orig/drivers/eisa/pci_eisa.c
> +++ linux-2.6/drivers/eisa/pci_eisa.c
> @@ -22,7 +22,8 @@ static struct eisa_root_device pci_eisa_
>  static int __init pci_eisa_init(struct pci_dev *pdev,
>                                 const struct pci_device_id *ent)
>  {
> -       int rc;
> +       int rc, n = 0;
> +       struct resource *bus_res;
>
>         if ((rc = pci_enable_device (pdev))) {
>                 printk (KERN_ERR "pci_eisa : Could not enable device %s\n",
> @@ -30,9 +31,12 @@ static int __init pci_eisa_init(struct p
>                 return rc;
>         }
>
> +       if (pci_is_root_bus(pdev->bus))
> +               n = PCI_BRIDGE_RESOURCE_NUM;
> +       bus_res = pci_bus_resource_n(pdev->bus, n);

I haven't figured out why the pci_is_root_bus() test is here.  Can you
explain, maybe with a sample dmesg log and "lspci -vvx" output?

Doesn't the 82375 subtractively decode this PCI memory space, the same
way a subtractive-decode P2P bridge does?  Can we  make this code look
like the "if (dev->transparent)" block in pci_read_bridge_bases(),
just breaking after the first resource we find, since
eisa_root_register() can only deal with a single resource on the EISA
bus?

Bjorn

>         pci_eisa_root.dev              = &pdev->dev;
> -       pci_eisa_root.res              = pdev->bus->resource[0];
> -       pci_eisa_root.bus_base_addr    = pdev->bus->resource[0]->start;
> +       pci_eisa_root.res              = bus_res;
> +       pci_eisa_root.bus_base_addr    = bus_res->start;
>         pci_eisa_root.slots            = EISA_MAX_SLOTS;
>         pci_eisa_root.dma_mask         = pdev->dma_mask;
>         dev_set_drvdata(pci_eisa_root.dev, &pci_eisa_root);
--
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