Re: Atari TT (next)

Alan Hourihane
2012-01-08T23:59:15Z

On 08/01/12 23:51, Michael Schmitz wrote:
> Hi Alan,
>
>>> Come to think of it - does the TT video chipset actually require
>>> screen memory to reside in ST-RAM? If it's fully 32 bit addressed we
>>> should not have any problems with TT-RAM. The problems you see might
>>> be caused by a fault in the TT codepath in atafb - I'm unsure this has
>>> been tested since the last atafb rewrite.
>> Looking at atafb, we always allocate FB memory from STRAM unless it's an
>> external video card, i.e. VME, ISA etc.
> That's right - but in your case ST-RAM is not being mapped at all so
> it can't be used. You will get a chunk of TT-RAM assigned to atafb
> (fallback in case there's no more ST-RAM), the framebuffer code will
> happily draw there but the shifter cannot access it.

I understand, but the STRAM allocator is broken. It gives out TT-RAM. It
should never do that on a TT.

>>> Can you try to have the kernel placed in ST-RAM?
>> No, the kernel is too big. I've only got 4MB ST-RAM. And getting more on
>> the TT is pretty rare as the only other option is 10MB using the onboard
>> 2MB and an 8MB upgrade board.
> You may have to pare the kernel down to the bare minimum (i.e.
> modularize about everything you don't need to boot to initrd). Not
> sure where the limit for this is these days.

Already tried that. Still too big, because we need buffers from STRAM too.

>>> You're right, this should be possible to test with ARAnyM - the
>>> behavior is not new though. Loading the kernel in TT-RAM has been
>>> problematic on the Falcon for a long time now.
>> Sure, but by default Falcon's have only 4MB ST-RAM too, and yes lots of
>> people have 14MB of ST-RAM now, but it's not uncommon to have 4MB ST-RAM.
> I think my Falcon is the only machine kernels have been tested on in
> the last few years - I've got 14MB ST-RAM so I was never affected. I
> had played with getting the kernel run in TT-RAM briefly but MM is not
> my strong suit so I never got anywhere.
>
>> I'll dig in.
> Much appreciated.
>

No probs. I'll report back when I have something.

Alan.