[RFC/PATCH 4/4] [POWERPC] pci: Disable IO/Mem on a device when resources can't be allocated

Benjamin Herrenschmidt
2007-12-17T23:02:28Z

This patch changes the PowerPC PCI code to disable IO and/or Memory
decoding on a PCI device when a resource of that type failed to be
allocated. This is done to avoid having unallocated dangling BARs enabled
that might try to decode on top of other devices.

If a proper resource is assigned later on, then pci_enable_device{,_io,_mem}
will take care of re-enabling decoding.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

NOTE: This patch doesn't apply on current upstream, but rather on top
of a serie that merges 32 and 64 bits PowerPC PCI resource handling, and
which will be in 2.6.25. I post it here mostly to show what I think should
be done. A similar patch will have to be done for other architectures.

arch/powerpc/kernel/pci-common.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

--- linux-work.orig/arch/powerpc/kernel/pci-common.c 2007-12-18 09:37:52.000000000 +1100
+++ linux-work/arch/powerpc/kernel/pci-common.c 2007-12-18 09:39:27.000000000 +1100
@@ -1016,7 +1016,7 @@ static void __init pcibios_allocate_bus_
}
}

-static inline void __devinit alloc_resource(struct pci_dev *dev, int idx)
+static inline int __devinit alloc_resource(struct pci_dev *dev, int idx)
{
struct resource *pr, *r = &dev->resource[idx];

@@ -1040,7 +1040,10 @@ static inline void __devinit alloc_resou
r->flags |= IORESOURCE_UNSET;
r->end -= r->start;
r->start = 0;
+
+ return -EBUSY;
}
+ return 0;
}

static void __init pcibios_allocate_resources(int pass)
@@ -1062,8 +1065,12 @@ static void __init pcibios_allocate_reso
disabled = !(command & PCI_COMMAND_IO);
else
disabled = !(command & PCI_COMMAND_MEMORY);
- if (pass == disabled)
- alloc_resource(dev, idx);
+ if (pass == disabled && alloc_resource(dev, idx)) {
+ command &= ~(r->flags & (IORESOURCE_IO |
+ IORESOURCE_MEM));
+ pci_write_config_word(dev,
+ PCI_COMMAND, command);
+ }
}
if (pass)
continue;