[coreboot] TV-Out Plan - need suggestions

Corey Osgood corey.osgood at gmail.com
Fri Apr 18 23:50:15 CEST 2008

On Fri, Apr 18, 2008 at 5:18 PM, Joe <joe at settoplinux.org> wrote:

> > Hello,
> > Starting to work on the TV-Out code for the RCA RM4100, and I need some
> > help. Here is the Logical Plan:
> >
> > 1. Setup a custom vga init (similar to Corey's vga.c for the cn700
> > northbridge) that will call a i2c (i810_i2c.c which could be used for a
> > bunch of intel nothbridges) driver from coreboot-v2/src/drivers/i2c/
> that
> > will setup communications with the Tv encoder via the GPIO (sda, sdl)
> > lines in the nothbridge.

Similar to, yes, but don't use vm86 (like I did) unless x86emu doesn't work.
What you can do is NOT set up the rom_address in Config.lb, so coreboot
doesn't know where to automagically run the rom from, then once you're done
with the pre-rom stuff, call pci_rom_run manually from a function inside
mainboard.c, using a location of 4GB-ROM_SIZE. Then in chip.h, add a struct
member .enable_dev = [name of your function], so your custom vga init is
only for your board.

> > 2. Then setup a init (that would program the registers, and fire it
> up)for
> > the Tv encoder coreboot-v2/src/drivers/tv-out which could also be called
> > from the nothbridge vga.c.

Again, do this inside mainboard.c, so any other systems that might use i830
don't get tv init interfering with anything else.

> >
> > Here is where it gets tricky. I want to make it dynamic in the respect
> > that you could specify from your mainboard directory:
> > a. TV-out settings (with a header file??) like NTSC, PAl, resolution,
> > macrovision, filters, etc.
> > a. enable TV encoder usage (if yes setup i2c, otherwise just skip over
> it)
> > b. Specify which Tv encoder to use

Two options:
The first is to add global defines to the mainboard Config.lb, which also
means adding them to the build system, I can't remember at the moment how to
do that, but I think if you grep for some config variable name in util/, and
you should be able to find it.

The second is to add config variables, similar to how we set the rom_address
= "0xsomething". That I can't remember how to do at the moment either, and
I'm not sure if you can do it on a mainboard level or not, thinking about it
again, you might have to resort to doing it in the northbridge stuff.

Good luck!

> >
> > This would broaden the horizons and allow other boards that have TV-out
> to
> > use this code also. The only thing I can think to do is setup some
> global
> > parameters? Suggestions?
> >
> >
> > --
> > Thanks,
> > Joseph Smith
> > Set-Top-Linux
> > www.settoplinux.org
> >
> > --
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> > coreboot at coreboot.org
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