[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>

diff --git a/arch/i386/boot/video.S b/arch/i386/boot/video.S
index 2c5b5cc..8143c95 100644 (file)
--- 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 d6ff88f..6090516 100644 (file)
--- 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, "