Rage128 support for resolutions less than panel resolution?

Rage128 support for resolutions less than panel resolution?

[Derrik Pates]

I know it's not in Ben's kernel yet, but I read something about adapting
the code that had been added to the Radeon framebuffer code to allow
resolutions lower than the LCD panel's native resolution (like on
laptops). I tried looking at the radeonfb source, and it's looking up a
devnode property on the display device that I don't see on this iBook
FireWire I'm using. (Specifically in the EDID reading code.)

What would need to be done to get (and set?) the EDID parameters on a
Rage128 with an LCD panel to make lower-than-native resolutions work on
the display? Any pointers?

Derrik Pates      |   Sysadmin, Douglas School   |    #linuxOS on EFnet
dpates@dsdk12.net |     District (dsdk12.net)    |    #linuxOS on OPN


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Re: Rage128 support for resolutions less than panel resolution?

[Kevin B. Hendricks]

Hi,

I don't think the EDID code has any impact on this.  It simply sets the
flatpanel monitor to its native resolution.  It isn't even used for LCD
monitors in the radeonfb.c

However if you have the correct timing info, you should be able to write a
mode to use and then use fbset to set rage128 frame buffer to that mode.

This should work to change your resolution to whatever you want as long as
the "scaling register code" patch I saw fly by recently (a couple of weeks
ago) actually made it into the aty128fb.c code yet.

If it did you should be in luck.  Just take the timing from the the full
native resolution and just change the x and y resolution and leave all of
the rest untouched.  The scaling registers code should figure out the rest.
as long as the real native panel resolution is known by the driver.

Here is what I do with a slightly modified version of the radeonfb.c

I edited my /etc/fb.modes to add the native resolution 1280x1024-FP
timings and them simply modified them to get 1024x768.  The radeonfb code
parses my monitor's EDID code so the true resolution of the flatpanel
monitor is known.  If is it not, you can pass in a panel_yres parameter
via the kernel parameters line.  aty128fb.c might have the same features.

mode "1024x768-FP"
    # D: 108.00 MHz, H: 63.981 kHz, V: 60.02 Hz
    geometry 1024 768 1024 768 8
    timings 9259 168 128 35 4 112 3
endmode


mode "1280x1024-FP"
    # D: 108.00 MHz, H: 63.981 kHz, V: 60.02 Hz
    geometry 1280 1024 1280 1024 8
    timings 9259 168 128 35 4 112 3
endmode

Hope this helps,

Kevin

On December 4, 2001 12:22, Derrik Pates wrote:
> I know it's not in Ben's kernel yet, but I read something about adapting
> the code that had been added to the Radeon framebuffer code to allow
> resolutions lower than the LCD panel's native resolution (like on
> laptops). I tried looking at the radeonfb source, and it's looking up a
> devnode property on the display device that I don't see on this iBook
> FireWire I'm using. (Specifically in the EDID reading code.)
>
> What would need to be done to get (and set?) the EDID parameters on a
> Rage128 with an LCD panel to make lower-than-native resolutions work on
> the display? Any pointers?
>
> Derrik Pates      |   Sysadmin, Douglas School   |    #linuxOS on EFnet
> dpates@dsdk12.net |     District (dsdk12.net)    |    #linuxOS on OPN
>
>

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Re: Rage128 support for resolutions less than panel resolution?

[Derrik Pates]

On Tue, 4 Dec 2001, Kevin B.Hendricks wrote:

> This should work to change your resolution to whatever you want as long as
> the "scaling register code" patch I saw fly by recently (a couple of weeks
> ago) actually made it into the aty128fb.c code yet.

Ah. I looked back through the folder I have for this list - turns out I
still had the message with the patch tacked on in the box! Yay! I'm
rebuilding the kernel (2.4.17-pre2-ben0, so no, it's not even in Ben's
tree yet) as I type, so hopefully this will make 640x480 work acceptably
on this iBook. It'd be nice for running MoL fullscreen, without having to
run it in 800x600 all the time...

Derrik Pates      |   Sysadmin, Douglas School   |    #linuxOS on EFnet
dpates@dsdk12.net |     District (dsdk12.net)    |    #linuxOS on OPN


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Re: Rage128 support for resolutions less than panel resolution?

[Derrik Pates]

The patch for stretching for lower panel resolutions is working perfectly
on this iBook. I did have to make a minor modification to aty128fb.c to
get it to work right, though - I had to add a section for PowerBook2,1 and
PowerBook2,2 compatible systems (that's all the round-case iBooks, with
and without FireWire) that set the info->panel_width and
info->panel_height variables to the correct values. I've noticed that the
'width' and 'height' properties of the ATY,RageM3p1 device node in
/proc/device-tree contain the actual panel dimensions, so that might be
all that's needed (at least on PPC systems, since they have a device tree)
to get the real panel dimensions.

Also, 'fbset 640x480-60' produces a slightly messed up display - the image
is squished to half-height, and doubled (same above and below) - but
640x480-72 and 640x480-75 both work correctly.

Derrik Pates      |   Sysadmin, Douglas School   |    #linuxOS on EFnet
dpates@dsdk12.net |     District (dsdk12.net)    |    #linuxOS on OPN


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Re: Rage128 support for resolutions less than panel resolution?

[Michel Dänzer]

On Tue, 2001-12-04 at 18:58, Kevin B. Hendricks wrote:

> However if you have the correct timing info, you should be able to write a
> mode to use and then use fbset to set rage128 frame buffer to that mode.
>
> This should work to change your resolution to whatever you want as long as
> the "scaling register code" patch I saw fly by recently (a couple of weeks
> ago) actually made it into the aty128fb.c code yet.
>
> If it did you should be in luck.  Just take the timing from the the full
> native resolution and just change the x and y resolution and leave all of
> the rest untouched.  The scaling registers code should figure out the rest.
> as long as the real native panel resolution is known by the driver.

Thanks for these instructions Kevin! I'm now able to use 800x600 and
640x480 on my Pismo without any flickering and artifacts.

One thing I noticed is that when I use the timings from 1024x768-60 for
640x480, the vertical refresh is shown as 130 Hz. That doesn't harm the
panel?


--
Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member   /  CS student, Free Software enthusiast

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Re: Rage128 support for resolutions less than panel resolution?

[Kevin B. Hendricks]

Hi,

> One thing I noticed is that when I use the timings from 1024x768-60 for
> 640x480, the vertical refresh is shown as 130 Hz. That doesn't harm the
> panel?

I don't know.  :-(

My limited understanding is that there is only one fixed timing for the
lcd and dfp displays and the stretch registers fill up the full horizontal
and vertical resolution (the same number of horizonntal and vertical bits
is always turned on) no matter what.  So the timing should be exactly the
same shouldn't it?

If you are worried you can try changing the refresh rate to see what
impact that has.

Sorry I can't be more help.

Take care,

Kevin


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