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

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Date:	Fri, 29 Mar 2013 16:30:02 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Whitehead <mwhitehe@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH 1/2] eisa, PCI: Fix bus res reference

On Fri, Mar 29, 2013 at 12:10:37PM -0700, Yinghai Lu wrote:
> On Fri, Mar 29, 2013 at 11:10 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> > On Wed, Mar 27, 2013 at 10:28 PM, Yinghai Lu <yinghai@...nel.org> 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@...hat.com>
> >> Tested-by: Matthew Whitehead <mwhitehe@...hat.com>
> >> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> >> Cc: stable@...nel.org
> >>
> >> ---
> >>  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?
> 
> Just forwarded two boot.log.
> 
> for  root bus, pci_bus_resource_n[0, PCI_BRIDGE_RESOURCE_NUM) all
> equal to 0.

Thanks.  The patch below is what I was thinking.  That should work
even in this scenario, I think, and it's nicer if we don't have to
have this root bus internal knowledge here.


diff --git a/drivers/eisa/pci_eisa.c b/drivers/eisa/pci_eisa.c
index cdae207..3e9dee9 100644
--- a/drivers/eisa/pci_eisa.c
+++ b/drivers/eisa/pci_eisa.c
@@ -22,7 +22,8 @@ static struct eisa_root_device pci_eisa_root;
 static int __init pci_eisa_init(struct pci_dev *pdev,
 				const struct pci_device_id *ent)
 {
-	int rc;
+	int rc, i;
+	struct resource *res;
 
 	if ((rc = pci_enable_device (pdev))) {
 		printk (KERN_ERR "pci_eisa : Could not enable device %s\n",
@@ -30,9 +31,28 @@ static int __init pci_eisa_init(struct pci_dev *pdev,
 		return rc;
 	}
 
+	/*
+	 * The Intel 82375 PCI-EISA bridge is a subtractive-decode PCI
+	 * device, so the resources available on EISA are the same as those
+	 * available on the 82375 bus.  This works the same as a PCI-PCI
+	 * bridge in subtractive-decode mode (see pci_read_bridge_bases()).
+	 * We assume other PCI-EISA bridges are similar.
+	 *
+	 * eisa_root_register() can only deal with a single resource, so we
+	 * use the first valid one.
+	 */
+	pci_bus_for_each_resource(pdev->bus, res, i)
+		if (res)
+			break;
+
+	if (!res) {
+		dev_err(&pdev->dev, "No resources available\n");
+		return -1;
+	}
+
 	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	       = res;
+	pci_eisa_root.bus_base_addr    = 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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