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SubjectRe: [PATCH]PCI:disable resource decode in PCI BAR detection
On Thu, Sep 13, 2007 at 09:32:42PM -0600, Robert Hancock wrote:
> Disabling the BAR decoding does not mean disabling the device (aside
> from the one group of host bridge that apparently disables CPU to RAM
> access, whose designers were apparently on crack when they read the PCI
> spec and which is why we don't disable the decode on host bridges).
> There really is no other sane way to do it.

Disabling IO and MEM decode effectively disables device as a PCI target.
Worse, it's often not just BARs that get disabled, but some non-standard
or hidden address ranges as well. Host bridges are just one common
example, there is a lot of other insane hardware, more than one could
expect.
BTW, the way how the internal address decode works on these latest Intel
whippets doesn't look sane either. ;-)

> If we do encounter other devices that choke on having the BAR disabled
> during probing then we can add additional quirk logic, but we haven't
> run into anything like that yet.

As Greg said, the main point is "no regression".

Folks, can you check if the patch below helps?

Ivan.

--- 2.6.23-rc6-git4/include/linux/pci.h 2007-09-12 17:22:57.000000000 +0400
+++ linux/include/linux/pci.h 2007-09-14 10:26:29.000000000 +0400
@@ -183,6 +183,7 @@ struct pci_dev {
unsigned int msi_enabled:1;
unsigned int msix_enabled:1;
unsigned int is_managed:1;
+ unsigned int disable_while_probe:1; /* Probe BARs with IO and MMIO turned off */
atomic_t enable_cnt; /* pci_enable_device has been called */

u32 saved_config_space[16]; /* config space saved at suspend time */
--- 2.6.23-rc6-git4/arch/i386/pci/fixup.c 2007-09-12 17:22:55.000000000 +0400
+++ linux/arch/i386/pci/fixup.c 2007-09-14 14:43:13.000000000 +0400
@@ -444,3 +444,21 @@ static void __devinit pci_siemens_interr
}
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_SIEMENS, 0x0015,
pci_siemens_interrupt_controller);
+
+/*
+ * Work around apparent quirk in internal address decoding on
+ * some Intel chipsets (G31, G33, Q965 etc.):
+ * when some MMIO address range of integrated peripheral overlaps
+ * mmconfig area, mmconfig accesses are blocked. This can happen
+ * when we size the BAR writing all ones to it.
+ * In practice, only integrated graphics controller has MMIO range
+ * large enough (BAR2, 256Mb) to cause a trouble, so we disable
+ * address decoders just on that function during PCI BAR probe.
+ */
+static void __devinit pci_intel_mmconfig(struct pci_dev *dev)
+{
+ if ((dev->class >> 8) == PCI_CLASS_DISPLAY_VGA &&
+ pci_domain_nr(dev->bus) == 0 && dev->bus->number == 0)
+ dev->disable_while_probe = 1;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_intel_mmconfig);
--- 2.6.23-rc6-git4/drivers/pci/probe.c 2007-09-14 00:35:47.000000000 +0400
+++ linux/drivers/pci/probe.c 2007-09-14 10:27:45.000000000 +0400
@@ -185,6 +185,13 @@ static void pci_read_bases(struct pci_de
unsigned int pos, reg, next;
u32 l, sz;
struct resource *res;
+ u16 cmd, orig_cmd;
+
+ if (dev->disable_while_probe) {
+ pci_read_config_word(dev, PCI_COMMAND, &orig_cmd);
+ cmd |= orig_cmd & ~(PCI_COMMAND_MEMORY | PCI_COMMAND_IO);
+ pci_write_config_word(dev, PCI_COMMAND, cmd);
+ }

for(pos=0; pos<howmany; pos = next) {
u64 l64;
@@ -283,6 +290,8 @@ static void pci_read_bases(struct pci_de
}
}
}
+ if (dev->disable_while_probe)
+ pci_write_config_word(dev, PCI_COMMAND, orig_cmd);
}

void pci_read_bridge_bases(struct pci_bus *child)
-
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