Ivan Kokshaysky wrote:
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.
Do you have an example of specific hardware that exhibits this problem?
So far after a similar patch has been in -mm for months there have been
no reports of any such problems.
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?
This isn't guaranteed to help. I don't think it is only integrated
graphics that could cause this problem, I think that an add-on PCI
Express card can do this as well. Depending on the chipset memory decode
rules, any PCI or PCI Express device with a BAR large enough could cause
issues.
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)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
