Re: [Linux-fbdev-devel] FB console clears with large white area at startup

[Sven <lu...@dp...>]

On Wed, Apr 24, 2002 at 10:44:18PM +0100, Jim Hague wrote:
> I've been using the Permedia2 driver on x86 for some time. I've always built
> the kernel with the VGA console and the pm2 driver built in.
> 
> So booting begins through the VGA console, and when the pm2 driver is loaded it
> grabs the console, up goes Tux and on we go. As you might expect.
> Except what actually happens is that most of the screen is cleared to white,
> and console messages appear on the bottom line of the white area. As the
> console scrolls the white area scrolls up the screen, though that part of it to
> the right of Tux remains as long as Tux remains.

I have the same problem with pm3fb.

From previous discution here, the culprit seems to be that the part of the
fbdev drvier responsible for getting the VGA text data and writing it to the
fbdev console is broken. 

If you have any fix to this, i would be very interested in it, to try to
duplicate it in pm3fb also.

> The size of the white area is the size of the VGA screen, both considered in
> terms of character positions. So with regular VGA it is 80x25. I tend to use
> 80x50 VGA, hence 'most' of the screen, my fb console size being 144x56.
> 
> For ages I thought this was a problem with the Permedia2 driver, and so have
> been giving myself an introduction to the console code digging around trying to
> find the problem. I haven't got to the bottom of it, but it looks to me like
> the problem is not a Permedia2 driver one, and that users of other drivers
> should see it to.

The difference is most probably that this is not broken for other drivers.
Maybe the main reason of this, is that both pm2fb and pm3fb were first
developped on plateforms without vga text console.

> Is this true? Is this an old chestnut that is well understood and has been done
> to death on the list in the past?

I think it is a known but unfixed problem, see previous posts about pm3fb on
this problem, especially responces to me by Petr with some vga black magic in
it.

> As far as I can tell at the moment, in take_over_console the outgoing console
> is suppose to save its screen contents (if visible) and these will be put onto
> the new console when update_screen() is called. Dumping the saved VGA screen,
> it seems that the saved screen consists entirely of 0x720, which I think
> explains the white. Why the VGA screen contents are like that I have, as yet, no
> idea.

But the traditional way of doing it may be broken on pm2fb.

i don't know, but while writing the pm3 X driver, i noticed that may board
will not save/restore the fonts correctly when doing MMIO (and when not doing
MMIO it would not work in dual pm3 configuration) so we (Well Alan Hourihane
actually) did change the code to read/save font memory using a special memcopy
instead of resorting to the vga interface, which seemed broken in this
respect. Maybe the pm2 chip shares this problem ?

BTW, what exact pm2 chip are you using ?

Friendly,

Sven Luther