Intel i915GM with SDVO CH7021A support?

Will . nodenet at
Tue Jan 2 15:19:23 PST 2007

>Hey, good work.

Thanks for the encouragement, much appreciated.

>Yes, please post the code. If you have a chance, I think you'll find the
>modesetting branch a lot easier to work in for this kind of thing, it
>has SDVO communication code all set up.

I think that's good advice (which I know I should have taken). Hopefully if 
there is time available to add support for this I'll pull the latest 
modesetting branch and try to put my changes in the correct places. I assume 
you'll want to minimize conditional branching etc as much as possible so if 
someone has the time to talk to me about whats required I'll do my best to 
contribute as appropriate.


//output connection (DAC select ?)

* memset(s->sdvo_regs, 0, 9);
* s->sdvo_regs[SDVO_I2C_ARG_0] = 0x4;
* s->sdvo_regs[SDVO_I2C_ARG_4] = 0x4;

//Composite= 0x4 DACB
//Component = 0x10; DACA
//Scart  = 0x20; DACC

The ports bellow were found using an incremental scan of the first 256 op 
codes (I used an xv hack and a shell script - probably not the best solution 
but it worked). Perhaps a better/alternative tactic may have been to look 
for opcodes that responded as it seems set/get pairs may travel in similar 
or adjoining locations.

The op codes listed may alter their range and function depending on the 
output type that is selected and possibly the tv format e.g. 
interlace/progressive. Most seem to support clock values. I've listed my 
notes with approximate defaults that relate to my setup, most of the notes 
relate to the component output I was using at the time.


approx 60 is def

96 - 0x60 (BRIGHTNESS)

approx 60 is def

99- 0x63 (WIDTH) Height is done with input timing

approx 28 is def


500 is def
520 is better

507 is correct for my display using scart


199 is correct for my display using scart (the default)


111 (FILTER??)


approx 60 is def 0=BW 100=SATURATED

90 (HUE)

approx 60 is def

45 (UNKNOWN - Causes display to blank and sync loss)

59 (UNKNOWN - Causes display to flash)


A corresponding modeline is required for the TV output to work, I think this 
can be generated using create preferred input timings (does this take note 
of the selected tv format). There is a relationship between input timing and 
output timings related to the tv format selected. I didn't notice much 
difference when playing with the sdvo output timings for this device, 
presumably output timings are fixed by the tv format.

Modeline "720x576_SDVO"   0.96 720 763 795 864  576 585 587 630 +vsync

#original from BIOS trace
#Modeline "720x576_SDVO"   0.96 720 756 788 864  576 616 618 700 +vsync

I made a corresponding adjustment to the 630 above in the input timings to 
get the overscan working as desired. There were some discrepancies between 
the original mode line from the bios trace (PAL 720x576 using 915resolution 
and vbetool) and the dtd that was created by create input timings, not sure 
if this is because I miss interpreted the data or due to some other reason. 
The only discrepancy was vsync offset which seemed way off.

When adjusting the overscan I reduced m in the PLL timings to gain a sync 
lock. I don't have the correct fixups for the PLL registers so I just used 
guess work, there is undoubtedly a proper way to calculate this but the full 
PLL routines may be required for them to be of any use.

e.g. I noticed the following not sure if its of any use though

3000/96/2=15.625 (Horizontal timing for PAL)

3000=clock value from create preferred input timings (ok  not exactly but 
96=the modeline clock from the BIOS trace
2=because its interlaced???

By adjusting the sync offset of the modeline horizontal/vertical position is 
adjustable in the normal way, I didn't adjust the input timing for this, 
there are sdvo op codes available for horiz/vert position anyway.

I've left sync disabled in ADPA, I think the sync is taken from 7021A's PLL 
anyway. I seem to remembed that if sync in ADPA is enabled that the CRT 
output will also be enabled, presumably with the TV timings from the 7021A. 
Perhaps this could be used to get exact tv timing for DVI if that isn't 
already possible

That's all I can remember for the moment hope this helps!

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