From 8660a1aa56caeb31bfaf15464285ca650638515e Mon Sep 17 00:00:00 2001 From: Kerry Sheh Date: Wed, 4 Jan 2012 20:51:47 +0800 Subject: [PATCH] Fix multipleVGA cards resource conflict on Windows If multiple VGA-compatible legacy graphic cards decode the IO range 3B0-3BB, 3C0-3DF and MEM range A00000-BFFFF. Windows 7 complain a resource conflict, so only one VGA card can works at the same time. There is a discussion in coreboot mail list before, please reference thread: "how to prevent legacy resource conflictwith multipleVGA cards" http://www.coreboot.org/pipermail/coreboot/2010-October/061508.html Linux using VGA Arbiter module(vgaarb) to resolve this resource conflict, Please see the following linux dmesg log, more information can be found in Linux source dir Documentation/vgaarbiter.txt. But it seems that windows don't dealwith this conflict. ~# dmesg | grep -i vgaarb [ 0.774076] vgaarb: device added: PCI:0000:00:01.0,decodes=io+mem,owns=io+mem [ 0.776065] vgaarb: device added: PCI:0000:01:00.0,decodes=io+mem,owns=none,l [ 0.780051] vgaarb: loaded [ 0.784049] vgaarb: bridge control possible 0000:01:00.0 [ 0.788050] vgaarb: bridge control possible 0000:00:01.0 For the second legacy graphic device, coreboot already disabled the IO and MEM decode in function set_vga_bridge_bits(). But it will be enabled again in function pci_set_resource(), if the second legacy vga-compatible graphic device take any IO/MEM resources. Following log printed by enable_resources() shows the problem: ...snip... PCI: 00:00.0 cmd <- 06 PCI: 00:01.0 subsystem <- 1022/1410 PCI: 00:01.0 cmd <- 07 <== The first graphic device PCI: 00:01.1 subsystem <- 1022/1410 PCI: 00:01.1 cmd <- 02 PCI: 00:02.0 bridge ctrl <- 0003 PCI: 00:02.0 cmd <- 07 ...snip... PCI: 01:00.0 cmd <- 03 <== The second graphic device PCI: 01:00.1 cmd <- 02 PCI: 02:00.0 cmd <- 02 PCI: 03:00.0 cmd <- 03 done. ...snip... The IO & MEM decoding on the second vga graphic device should be disabled. Please reference PCI spec. section 3.10 in detail. set_vga_bridge_bits() would do this work for us, it did the right thing, but was put to the wrong place, the setting would be overwritten by assign_resources() later. In order to make sure the set_vga_bridge_bits() setting not be overwritten by others, moving the call of set_vga_bridge_bits() to the end of dev_configure(), instead of at the beginning. This patch resolved the dual graphic cards resource conflict in windows7, multiple vga-compatible graphic cards can work together in windows7. Signed-off-by: Kerry Sheh Signed-off-by: Kerry Sheh Change-Id: I0de5e3761b51e2723d9c1dc0c39fff692e3a779d Reviewed-on: http://review.coreboot.org/489 Tested-by: build bot (Jenkins) Reviewed-by: Marc Jones --- src/devices/device.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/devices/device.c b/src/devices/device.c index a2619bf000..8ad9787431 100644 --- a/src/devices/device.c +++ b/src/devices/device.c @@ -932,10 +932,6 @@ void dev_configure(void) struct device *root; struct device *child; -#if CONFIG_VGA_BRIDGE_SETUP == 1 - set_vga_bridge_bits(); -#endif - printk(BIOS_INFO, "Allocating resources...\n"); root = &dev_root; @@ -1028,6 +1024,10 @@ void dev_configure(void) printk(BIOS_INFO, "Done setting resources.\n"); print_resource_tree(root, BIOS_SPEW, "After assigning values."); +#if CONFIG_VGA_BRIDGE_SETUP == 1 + set_vga_bridge_bits(); +#endif + printk(BIOS_INFO, "Done allocating resources.\n"); }