[PATCH] x86: Don't probe for DDC on VBE1.2

VBE1.2 doesn't support function 15h (DDC) resulting in a 'hang' whilst
uncompressing kernel with some video cards. Make sure we check VBE version
before fiddling around with DDC.

http://bugzilla.kernel.org/show_bug.cgi?id=1458

Opened: 2003-10-30 09:12 Last update: 2007-02-13 22:03

Much thanks to Tobias Hain for help in testing and investigating the bug.
Tested on;

i386, Chips & Technologies 65548 VESA VBE 1.2
CONFIG_VIDEO_SELECT=Y
CONFIG_FIRMWARE_EDID=Y

Untested on x86_64.

Signed-off-by: Zwane Mwaikambo <zwane@infradead.org>
Signed-off-by: Andi Kleen <ak@suse.de>

2 files changed, 28 insertions, 0 deletions

diff --git a/arch/i386/boot/video.S b/arch/i386/boot/video.S
index 2c5b5cc55f79..8143c9516cb4 100644
--- a/arch/i386/boot/video.S
+++ b/arch/i386/boot/video.S
@@ -571,6 +571,16 @@ setr1:	lodsw
         jmp     _m_s
 
 check_vesa:
+#ifdef CONFIG_FIRMWARE_EDID
+        leaw    modelist+1024, %di
+        movw    $0x4f00, %ax
+        int     $0x10
+        cmpw    $0x004f, %ax
+        jnz     setbad
+
+        movw    4(%di), %ax
+        movw    %ax, vbe_version
+#endif
         leaw    modelist+1024, %di
         subb    $VIDEO_FIRST_VESA>>8, %bh
         movw    %bx, %cx                        # Get mode information structure
@@ -1945,6 +1955,9 @@ store_edid:
         rep
         stosl
 
+        cmpw    $0x0200, vbe_version            # only do EDID on >= VBE2.0
+        jl      no_edid
+
         pushw   %es                             # save ES
         xorw    %di, %di                        # Report Capability
         pushw   %di
@@ -1987,6 +2000,7 @@ do_restore:	.byte	0	# Screen contents altered during mode change
 svga_prefix:    .byte   VIDEO_FIRST_BIOS>>8     # Default prefix for BIOS modes
 graphic_mode:   .byte   0       # Graphic mode with a linear frame buffer
 dac_size:       .byte   6       # DAC bit depth
+vbe_version:    .word   0       # VBE bios version
 
 # Status messages
 keymsg:         .ascii  "Press <RETURN> to see video modes available, "
diff --git a/arch/x86_64/boot/video.S b/arch/x86_64/boot/video.S
index d6ff88f35135..6090516c9c7f 100644
--- a/arch/x86_64/boot/video.S
+++ b/arch/x86_64/boot/video.S
@@ -571,6 +571,16 @@ setr1:	lodsw
         jmp     _m_s
 
 check_vesa:
+#ifdef CONFIG_FIRMWARE_EDID
+        leaw    modelist+1024, %di
+        movw    $0x4f00, %ax
+        int     $0x10
+        cmpw    $0x004f, %ax
+        jnz     setbad
+
+        movw    4(%di), %ax
+        movw    %ax, vbe_version
+#endif
         leaw    modelist+1024, %di
         subb    $VIDEO_FIRST_VESA>>8, %bh
         movw    %bx, %cx                        # Get mode information structure
@@ -1945,6 +1955,9 @@ store_edid:
         rep
         stosl
 
+        cmpw    $0x0200, vbe_version            # only do EDID on >= VBE2.0
+        jl      no_edid
+
         pushw   %es                             # save ES
         xorw    %di, %di                        # Report Capability
         pushw   %di
@@ -1987,6 +2000,7 @@ do_restore:	.byte	0	# Screen contents altered during mode change
 svga_prefix:    .byte   VIDEO_FIRST_BIOS>>8     # Default prefix for BIOS modes
 graphic_mode:   .byte   0       # Graphic mode with a linear frame buffer
 dac_size:       .byte   6       # DAC bit depth
+vbe_version:    .word   0       # VBE bios version
 
 # Status messages
 keymsg:         .ascii  "Press <RETURN> to see video modes available, "