diff options
| author | Keith Busch <keith.busch@intel.com> | 2016-03-02 15:31:03 -0700 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2016-03-10 14:52:13 -0600 |
| commit | 83cc54a608b66d3fffa7355503263d20f491bb44 (patch) | |
| tree | dad3fe08459f1f0f0402e982f41b34f9b36f38cd | |
| parent | 92e963f50fc74041b5e9e744c330dca48e04f08d (diff) | |
x86/PCI: VMD: Document code for maintainability
Comment the less obvious portion of the code for setting up memory windows,
and the platform dependency for initializing the h/w with appropriate
resources.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
| -rw-r--r-- | arch/x86/pci/vmd.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/x86/pci/vmd.c b/arch/x86/pci/vmd.c index d57e48016f15..29aebbcb510b 100644 --- a/arch/x86/pci/vmd.c +++ b/arch/x86/pci/vmd.c @@ -532,6 +532,23 @@ static int vmd_enable_domain(struct vmd_dev *vmd) .flags = IORESOURCE_BUS | IORESOURCE_PCI_FIXED, }; + /* + * If the window is below 4GB, clear IORESOURCE_MEM_64 so we can + * put 32-bit resources in the window. + * + * There's no hardware reason why a 64-bit window *couldn't* + * contain a 32-bit resource, but pbus_size_mem() computes the + * bridge window size assuming a 64-bit window will contain no + * 32-bit resources. __pci_assign_resource() enforces that + * artificial restriction to make sure everything will fit. + * + * The only way we could use a 64-bit non-prefechable MEMBAR is + * if its address is <4GB so that we can convert it to a 32-bit + * resource. To be visible to the host OS, all VMD endpoints must + * be initially configured by platform BIOS, which includes setting + * up these resources. We can assume the device is configured + * according to the platform needs. + */ res = &vmd->dev->resource[VMD_MEMBAR1]; upper_bits = upper_32_bits(res->end); flags = res->flags & ~IORESOURCE_SIZEALIGN; |