Only try to enable a 64bit window on AMD CPUs when pci=big_root_window is
specified and taint the kernel when we add the window.
v2: add documentation for the new option.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++++
arch/x86/include/asm/pci_x86.h | 1 +
arch/x86/pci/common.c | 5 +++++
arch/x86/pci/fixup.c | 4 ++++
4 files changed, 14 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6571fbfdb2a1..0cf9e3785840 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3094,6 +3094,10 @@
pcie_scan_all Scan all possible PCIe devices. Otherwise we
only look for one device below a PCIe downstream
port.
+ big_root_window Try to add a big 64bit memory window to the PCIe
+ root complex on AMD CPUs. This is useful for GFX
+ hardware which can resize their PCIe BAR to
+ allow full CPU access to VRAM.
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
index 7a5d6695abd3..eb66fa9cd0fc 100644
--- a/arch/x86/include/asm/pci_x86.h
+++ b/arch/x86/include/asm/pci_x86.h
@@ -38,6 +38,7 @@ do { \
#define PCI_NOASSIGN_ROMS 0x80000
#define PCI_ROOT_NO_CRS 0x100000
#define PCI_NOASSIGN_BARS 0x200000
+#define PCI_BIG_ROOT_WINDOW 0x400000
extern unsigned int pci_probe;
extern unsigned long pirq_table_addr;
diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 7a5350d08cef..563049c483a1 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -594,6 +594,11 @@ char *__init pcibios_setup(char *str)
} else if (!strcmp(str, "nocrs")) {
pci_probe |= PCI_ROOT_NO_CRS;
return NULL;
+#ifdef CONFIG_PHYS_ADDR_T_64BIT
+ } else if (!strcmp(str, "big_root_window")) {
+ pci_probe |= PCI_BIG_ROOT_WINDOW;
+ return NULL;
+#endif
} else if (!strcmp(str, "earlydump")) {
pci_early_dump_regs = 1;
return NULL;
diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index e663d6bf1328..a91280da2ea1 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -667,6 +667,9 @@ static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
struct resource *res, *conflict;
struct pci_dev *other;
+ if (!(pci_probe & PCI_BIG_ROOT_WINDOW))
+ return;
+
/* Check that we are the only device of that type */
other = pci_get_device(dev->vendor, dev->device, NULL);
if (other != dev ||
@@ -715,6 +718,7 @@ static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
}
dev_info(&dev->dev, "adding root bus resource %pR\n", res);
+ add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
base = ((res->start >> 8) & AMD_141b_MMIO_BASE_MMIOBASE_MASK) |
AMD_141b_MMIO_BASE_RE_MASK | AMD_141b_MMIO_BASE_WE_MASK;
--
2.11.0
