Re: Improving Performance

[Michael Schmitz <schmitz@biophys.uni-duesseldorf.de>]

Stefan,

> > Adding an option to the atafb video driver make use of the SuperVidel
> > hardware would be the easiest option. The SuperVidel base address is
> > fixed, and it can use any chunk of FastRAM for frame buffer, 
> > presumably?
>
> The SuperVidel has 128MB Video RAM (DDR2 SDRAM):

Thanks, that'll make it easier, we just need to ioremap a chunk of the 
video RAM.

> 0xA0000000 16MB - this is a shadow of ST RAM in DDR2 SDRAM
> Write access to ST RAM will be sniffed and done to the shadow RAM 
> automagically.

We can't write to ST-RAM if the kernel is in FastRAM, for now. The bus 
snooping is done for the entire 16 MB, in hardware? The atafb driver 
would need to keep well clear of that segment if ST-RAM is used by the 
kernel (i.e. kernel in ST-RAM).

> 0xA1000000 112MB - this is the general purpose Video/graphics RAM
> Can be read/write accessed as Byte/Word/Long
>
>
> Here you can find the SV memory map: 
> http://hencox.dyndns.org/homepage/Self/SuperVidelMemoryMap.pdf

Thanks, that might come in handy.

> > In that case, it might be sufficient to change the fixed Videl base
> > address to a variable one in the atafb driver, and perhaps use kmalloc
> > instead of stram_alloc to allocate the frame buffer. If someone with
> > access to this hardware is interested in giving this a try, I'd be 
> > happy
> > to elaborate.
>
> Yeah, i'd be happy to try.

OK, I'll have a look at the atafb code and try to see where it will 
need changes.
Replacing stram_alloc by ioremap of a chunk at 0xA1000000 and 
hardcoding the Videl base address for that of the Supervidel (if 
necessary) is what I'd try first.

> > (You'd need to compile your own kernels, and having a serial cable
> > between the SCC modem port and some other computer for capturing 
> > kernel
> > boot logs would be a clear bonus.)
>
> I can surely need a helping hand in this, (compile kernel) but i found
> someone who showed me how to set up a crosscompiler and kernelconfig.

The last crosscompiler I got was from kernel.org, following a hint from 
Geert. I can provide a fairly minimal .config (for CT60, so no 030 
support).

Geert's Atari defconfig ought to be a good starting point, too.

Cheers,

	Michael


> Will figure out.
>
> Thanks so far,
> Stefan
>
>
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