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List:       freedesktop-xorg
Subject:    Re: [Intel-gfx] VGA to PAL RGB
From:       Thomas Hilber <xorg () toh ! cx>
Date:       2008-07-31 8:15:26
Message-ID: 20080731081526.GA11078 () roja ! toh ! cx
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On Thu, Jul 24, 2008 at 12:21:14PM +0200, Thomas Elsen wrote:
> I'm trying to get the following modeline to work with my Mythbuntu. This 
> modeline should be perfect for television sets that understand PAL.
> 
> Modeline "768x576pali" 14.76  768 789 858 944  576 580 583 625 -hsync 
> -vsync interlace
[...]

> The problem with the current drivers is that the minimal dot clock is 
> defined as 25Mhz. I'd like to know if this is a hardware limitation and, 
> if not, what should be done to run the clock at 14,76Mhz.
[...]

For my current project

english:
http://linuxtv.org/pipermail/vdr/2008-July/017347.html

german:
http://www.vdr-portal.de/board/thread.php?threadid=78480

I experiment a lot with VGA->SCART adaptors. In the meantime I
get excellent picture quality on Radeons like (7000, 9200SE, 9250,
9600SE, IGP-9100). This is because no deinterlacing at all takes place
any more. I route the untouched fields from softdecoder straight through
to the VGA port! I developed a new synchronization mechanism that avoids 
any field loss. Please see links above for more information.

Yesterday I started to port this thing to intel DDX. Please find
attached a patch that allows you to use such low dot clocks on intel
hardware. I don't know what these limits in the standard intel code are
good
for. BTW I use a thinkpad with mobile GM965/GL960 chipset for my tests.
Maybe you must adapt the patch to your needs.

But there exist still some issues with intel-gfx and interlaced modes:

Using the overlay XV adaptor I only get a green picture...
Using the textured XV adaptor the picture is vertically stretched (if
not
doubled)...

So for the moment I stopped further activities with intel-gfx.

Maybe the situation has improved since xf86-video-intel 2.4.0. I haven't
had the time yet to give it a try.

-Thomas


["intel-gfx-low-dotclk.patch" (application/x-patch)]

diff -ur xserver-xorg-video-intel-2.3.2/src/i830_crt.c \
                xserver-xorg-video-intel-2.3.2.patched/src/i830_crt.c
--- xserver-xorg-video-intel-2.3.2/src/i830_crt.c	2008-03-26 03:15:53.000000000 +0100
+++ xserver-xorg-video-intel-2.3.2.patched/src/i830_crt.c	2008-07-30 \
14:09:19.000000000 +0200 @@ -87,7 +87,7 @@
     if (pMode->Flags & V_DBLSCAN)
 	return MODE_NO_DBLESCAN;
 
-    if (pMode->Clock > 400000 || pMode->Clock < 25000)
+    if (pMode->Clock > 400000 || pMode->Clock < 12000)
 	return MODE_CLOCK_RANGE;
 
     return MODE_OK;
diff -ur xserver-xorg-video-intel-2.3.2/src/i830_display.c \
                xserver-xorg-video-intel-2.3.2.patched/src/i830_display.c
--- xserver-xorg-video-intel-2.3.2/src/i830_display.c	2008-06-17 03:49:16.000000000 \
                +0200
+++ xserver-xorg-video-intel-2.3.2.patched/src/i830_display.c	2008-07-30 \
14:14:33.000000000 +0200 @@ -71,7 +71,7 @@
     intel_p2_t	    p2;
 } intel_limit_t;
 
-#define I8XX_DOT_MIN		  25000
+#define I8XX_DOT_MIN		  12000
 #define I8XX_DOT_MAX		 350000
 #define I8XX_VCO_MIN		 930000
 #define I8XX_VCO_MAX		1400000
@@ -95,9 +95,9 @@
 #define I8XX_P2_LVDS_FAST	      7
 #define I8XX_P2_SLOW_LIMIT	 165000
 
-#define I9XX_DOT_MIN		  20000
+#define I9XX_DOT_MIN		  12000
 #define I9XX_DOT_MAX		 400000
-#define I9XX_VCO_MIN		1400000
+#define I9XX_VCO_MIN		1000000
 #define I9XX_VCO_MAX		2800000
 
 /* Haven't found any reason to go this fast, but newer chips support it */



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