[PATCH]; drivers/pci.c kernel-2.4.7

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Here is a tested patch to pci_find_parent_resource(dev,res) in 
drivers/pci.c. (Patch is against 2.4.7; attached as tarball)  
Problem occurs in all 2.4.x kernels.

PROBLEM: when allocating resource regions for PCI device dev at boot, 
only the resources of its parent bus dev->bus are searched.

I have an nvidia AGP card on 01:00.0 which requires PCI MEM which is a
resource of the PCI bridge 00:01.0.   

bus [01] = dev->bus gets searched, but nothing is found; the card is 
not configured. 

lspci -t  shows the pci bus tree:

-[00]-+-00.0
      +-01.0-[01]---00.0
      +-07.0
      etc

SOLUTION: if bus = dev->bus has no relevant resources listed,
try bus->parent, if != NULL.  Recursively search resources of parents,
grandparents, etc. of bus.  In my case, the resource is found on [00],
and the card works.

QUESTION: Is it in general OK to allow "upstream" resource regions 
to be allocated to a device?   Maybe only dev->bus  and dev->bus->parent 
should be searched.  (My patch will keep searching all the way to the
top)

Please CC any comments to me at [e-mail].

Duncan Haldane.

------------

diff -uNr linux-2.4.7/drivers/pci/pci.c linux-2.4.7-pci_patch/drivers/pci/pci.c
--- linux-2.4.7/drivers/pci/pci.c       Thu Aug  9 02:36:31 2001
+++ linux-2.4.7-pci_patch/drivers/pci/pci.c     Thu Aug  9 13:13:02 2001
@@ -202,17 +202,18 @@
  * @res: child resource record for which parent is sought
  *
  *  For given resource region of given device, return the resource
- *  region of parent bus the given region is contained in or where
- *  it should be allocated from.
+ *  region of the parent bus (or recursively of its parents) in which the given
+ *  region is contained in or where it should be allocated from.
  */
 struct resource *
 pci_find_parent_resource(const struct pci_dev *dev, struct resource *res)
 {
-       const struct pci_bus *bus = dev->bus;
+       struct pci_bus *bus = dev->bus;
        int i;
        struct resource *best = NULL;
 
-       for(i=0; i<4; i++) {
+       while (bus) {
+         for(i=0; i<4; i++) {
                struct resource *r = bus->resource[i];
                if (!r)
                        continue;
@@ -224,6 +225,10 @@
                        return r;       /* Exact match */
                if ((res->flags & IORESOURCE_PREFETCH) && !(r->flags &
IORESOURCE_PREFETCH))
                        best = r;       /* Approximating prefetchable by
non-prefetchable */
+         }
+         if (best)
+           return best;
+         bus = bus->parent;  /* If nothing found, recursively search parent */
        }
        return best;
 }

----------------------------------
E-Mail: [e-mail]
Date: 11-Aug-2001
Time: 00:51:42

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