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Subject[PATCH] Use EDID/DDC data to set better refreshrates on VBE3.0+ videocards on boot
Hi,

The following patch requests EDID data from the monitor/graphics card,
check it against the vga= setting the user set and when it finds a match
sets the refresh rate to the EDID supplied mode (So should be safe, even
on broken biosses). This makes working in vesafb mode _allot_ better for
your eyes. If either no vesa 3.0 card or VBE/DC EDID data is available
it just sets the vesa graphic mode the old tried and tested way (60Hz ugh!).

I have tested the patch on the following cards with different feature
support (All same type monitor though):

- Geforce2 MX/MX 400: Working at 85hz
- Geforce 256 SDR: Working at 85Hz
- GeForce2 - nForce GPU: Not working, no EDID data available
- VMWare v4: Not working, not a VBE v3.00 card

Not working, in this case, means that it just used normal 60hz vesa
mode. The graphic mode was otherwise working fine.

What do you think? :)

Other patches:
http://nitrate.et.tudelft.nl/~sander/patches/linux-2.4.20-vesa-edid.patch
http://nitrate.et.tudelft.nl/~sander/patches/linux-2.6.0-test2-vesa-edid.patch

Patch for v2.4.20 and v2.4.21 (the same):

--- Documentation/fb/vesafb.txt.orig 2003-08-03 16:05:25.000000000 +0200
+++ Documentation/fb/vesafb.txt 2003-08-03 16:14:38.000000000 +0200
@@ -97,11 +97,17 @@

* configure and load the DOS-Tools for your the graphics board (if
available) and boot linux with loadlin.
- * use a native driver (matroxfb/atyfb) instead if vesafb. If none
+ * use a native driver (matroxfb/atyfb) instead of vesafb. If none
is available, write a new one!
- * VBE 3.0 might work too. I have neither a gfx board with VBE 3.0
- support nor the specs, so I have not checked this yet.

+If you have a VBE 3.0 card and your monitor and graphic card combination
+support VBE/DC, linux will attempt to set the monitor supplied refresh
+rates before linux is loaded. This will happen automagicly when you supply
+your kernel with a vga= option. If this for some reason fails and leaves
+you stuck with 60 Hz, you can use read-edid (1) to see if and what modes
+your monitor reports to the kernel.
+
+(1) http://tcsu.trin.cam.ac.uk/~john/programs/linux/read-edid/

Configuration
=============
--- arch/i386/boot/video.S.orig 2003-08-03 13:31:47.000000000 +0200
+++ arch/i386/boot/video.S 2003-08-03 13:33:40.000000000 +0200
@@ -19,6 +19,13 @@
/* Enable autodetection of VESA modes */
#define CONFIG_VIDEO_VESA

+/* Enable setting better monitor timings when using a VESA v3 videocard */
+#ifndef CONFIG VIDEO_VESA
+# undef CONFIG_VIDEO_VESA_TIMINGS
+#elseif
+# define CONFIG_VIDEO_VESA_TIMINGS
+#endif
+
/* Enable compacting of mode table */
#define CONFIG_VIDEO_COMPACT

@@ -453,7 +460,7 @@

cmpb $VIDEO_FIRST_V7>>8, %ah
jz setv7
-
+
cmpb $VIDEO_FIRST_VESA>>8, %ah
jnc check_vesa

@@ -549,6 +556,133 @@
jnz _setbad # Doh! No linear frame buffer.

subb $VIDEO_FIRST_VESA>>8, %bh
+
+#ifdef CONFIG_VIDEO_VESA_TIMINGS
+
+ movw %di, %si # need resolution info later
+
+ leaw modelist+512, %di # using 512b temporary space
+
+ movw 0x02B3, %ax
+ movw %ax, (%di)
+ movw 0x9D4A, %ax
+ movw %ax, 2(%di) # set signature to "vbe2"
+
+ movw $0x4f00, %ax
+ int $0x10
+
+ cmpw $0x004f, %ax
+ jne bios_def_tim
+
+ cmpw $0x300, 4(%di)
+ jne bios_def_tim # no vesa v3+, so no timings support
+
+ pusha
+
+ call store_edid
+
+ leaw modelist+2102, %di # point to monitor detailed timing (2048+0x36)
+
+ movw $5, %cx
+chk_vactive:
+ movb 7(%di), %ah
+ shrb $4, %ah
+ movb 5(%di), %al
+
+ cmpw 20(%si), %ax # check against vactive
+ je chk_hactive # is the vertical resolution the same?
+
+ addw $0x12, %di
+ decw %cx
+ jnz chk_vactive
+
+ #failed
+
+ popa
+ jmp bios_def_tim # our mode is not there :(
+
+chk_hactive:
+ movb 4(%di), %ah
+ shrb $4, %ah
+ movb 2(%di), %al
+
+ cmpw 18(%si), %ax
+ je calc_timings # we have a winner
+
+ addw $0x12, %di
+ decw %cx
+ jnz chk_vactive
+
+ #definatly failed
+ popa
+ jmp bios_def_tim
+
+calc_timings: # (%ax has hactive)
+
+ movb 4(%di), %dh # get hblanking
+ andb $15, %dh
+ movb 3(%di), %dl
+ addw %ax, %dx # hactive + hblanking
+ movw %dx, htotal
+
+ movb 11(%di), %dh # get hsync_offset
+ shrw $6, %dx
+ movb 8(%di), %dl
+ addw %ax, %dx # hactive + hsync_offset
+
+ movw %dx, hsyncstart
+
+ movb 11(%di), %ah # get hsync_width (%dx holds hsyncstart)
+ andb $48, %ah
+ shrb $4, %ah
+ movb 9(%di), %al
+ addw %dx, %ax # hsyncstart + hsync_width
+ movw %ax, hsyncend
+
+ movw 20(%si), %ax # move in vactive
+
+ movb 7(%di), %dh # get vblanking
+ andb $15, %dh
+ movb 6(%di), %dl
+ addw %ax, %dx # vactive + vblanking
+ movw %dx, vtotal
+
+ movb 11(%di), %dh # get vsync start
+ andb $12, %dh
+ shrb $2, %dh
+ movb 10(%di), %dl
+ shrb $4, %dl
+ addw %ax, %dx # vactive + voffset
+ movw %dx, vsyncstart
+
+ movb 11(%di), %ah # get vsync width (%dx holds sycnstart)
+ andb $3, %ah
+ movb 10(%di), %al
+ andb $15, %al
+ addw %dx, %ax
+ movw %ax, vsyncend
+
+ movw (%di), %ax # get pixclock
+ imul $10000, %eax, %eax
+ movl %eax, pixelclock
+
+ #todo: refreshrate ( pixelclock / ( htotal * vtotal ) * 100 ), unused?
+
+ movb 17(%di), %al
+ testb $127, %al # interlaced mode?
+ jnz vbe_supplied_tim
+
+ movb $127, monflags
+
+vbe_supplied_tim:
+ popa
+
+ leaw crtcinfoblock, %di
+ orw $0x0800, %bx # we got our own timing...
+bios_def_tim:
+
+#endif /* CONFIG_VIDEO_VESA_TIMINGS */
+
orw $0x4000, %bx # Use linear frame buffer
movw $0x4f02, %ax # VESA BIOS mode set call
int $0x10
@@ -1884,6 +2018,29 @@
popw %ax
ret

+store_edid:
+
+ pusha
+
+ movw $0x1313, %ax
+ movw $64, %cx
+ leaw modelist+2048, %di
+ rep stosw
+
+ leaw modelist+2048, %di
+
+ movw $0x4f15, %ax
+ movw $0x01, %bx
+ movw %bx, %dx
+ xorw %cx, %cx
+ int $0x10
+
+ popa
+
+ ret
+
+
+
# VIDEO_SELECT-only variables
mt_end: .word 0 # End of video mode table if built
edit_buf: .space 6 # Line editor buffer
@@ -1932,3 +2089,19 @@
adapter: .byte 0 # Video adapter: 0=CGA/MDA/HGA,1=EGA,2=VGA
video_segment: .word 0xb800 # Video memory segment
force_size: .word 0 # Use this size instead of the one in BIOS vars
+
+#ifdef CONFIG_VIDEO_VESA_TIMINGS
+
+crtcinfoblock: /* going to be written by vbe/dc code */
+htotal: .word 0
+hsyncstart: .word 0
+hsyncend: .word 0
+vtotal: .word 0
+vsyncstart: .word 0
+vsyncend: .word 0
+monflags: .byte 0
+pixelclock: .long 0
+refreshrate: .word 0
+filler: .space 40
+
+#endif /* CONFIG_VIDEO_VESA_TIMINGS






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