[PATCH 1/1] Fix PCIe LER when GRUB2 accesses non-enabled MMIO data from VGA

[mike.travis]

A GPU inserted into a PCIe I/O slot disappears during system startup.
The problem centers around GRUB and a specific VGA init function in
efi_uga.c.  This causes an LER (link error recorvery) because the MMIO
memory has not been enabled before attempting access.

The fix is to add the same coding used in other VGA drivers, specifically
to add a check to insure that it is indeed a VGA controller.  And then
enable the MMIO address space with the specific bits.

Signed-off-by: Mike Travis <address@hidden>
Reviewed-by: Michael Chang <address@hidden>
Reviewed-by: Daniel Kiper <address@hidden>
---
v1:change class to subclass, remove parens around "enable mem" code
---
 grub-2.02/grub-core/video/efi_uga.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Index: grub-2.02/grub-core/video/efi_uga.c
===================================================================
--- grub-2.02.orig/grub-core/video/efi_uga.c
+++ grub-2.02/grub-core/video/efi_uga.c
@@ -95,9 +95,18 @@ find_card (grub_pci_device_t dev, grub_p
 {
   struct find_framebuf_ctx *ctx = data;
   grub_pci_address_t addr;
+  grub_pci_address_t rcaddr;
+  grub_uint32_t subclass;
 
   addr = grub_pci_make_address (dev, GRUB_PCI_REG_CLASS);
-  if (grub_pci_read (addr) >> 24 == 0x3)
+  subclass = (grub_pci_read (addr) >> 16) & 0xffff;
+  if (subclass != GRUB_PCI_CLASS_SUBCLASS_VGA)
+    return 0;
+
+  /* Enable MEM address spaces */
+  rcaddr = grub_pci_make_address (dev, GRUB_PCI_REG_COMMAND);
+  grub_pci_write_word (rcaddr, grub_pci_read_word (rcaddr) | 
GRUB_PCI_COMMAND_MEM_ENABLED);
+
     {
       int i;
 

--