Re: controlfb: please test!

Well, first of all, there are two different 'current' controlfb's.  One
of them is in the PPC 2.2 tree and the other in the 2.3 tree (both
bitkeeper), I believe.  Did you try both of those?  I'm pretty sure I
fixed this quite thoroughly in one or the other.

I admit (ashamedly) to not remembering which.

Actually, on closer look, I thought that the 2.3 code was correct.
Could you compare to Andrew's observations in the comment above the
code?  Is he wrong?  I certainly can't see how his comment would be
unless there is a memory scheme he was not detecting, and I do not
think there is.

I have a bunch of other patches to merge for controlfb anyway, so now
is a good time to straighten this out... with luck and speed we can get
a fix into 2.3.99preX.

On Sat, Mar 18, 2000 at 10:03:05AM +0100, Michel Lanners wrote:

Hi list,

You may remeber my problems (and the many other problems reported over
the years ;-) with controlfb's detection of the amount of VRAM
installed.

Well, it seems control has some bugs, which makes detection less easy,
and until now, only one of two possible schemes for the memory layout
was correctly detected.

Well, I think it's time to clean this mess up, so I want _all_
developers with any machine that has the control hardware
(PowerMacs 7300, 7500, 7600, 8500, 8600, clones?) to try the following
patch on a 2.3 kernel, and report the results to me.

Mine look like this, with 2 MB in bank2:
....
control: mem at 0x000000: no
control: mem at 0x200000: no
control: mem at 0x400000: no
control: mem at 0x600000: yes
controlfb: Memory bank 1 absent, bank 2 present, total VRAM 2MB
....

Please include yur VRAM configuration, and if you have the time, please
try all possible combinations (2MB in either bank1 or bank2, and 4MB).

Dan

/--------------------------------\  /--------------------------------\
|       Daniel Jacobowitz        |__|        SCS Class of 2002       |
|   Debian GNU/Linux Developer    __    Carnegie Mellon University   |
|         dan@debian.org         |  |       dmj+@andrew.cmu.edu      |
\--------------------------------/  \--------------------------------/

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Hi Dan,

On  18 Mar, this message from Daniel Jacobowitz echoed through cyberspace:

Well, first of all, there are two different 'current' controlfb's.  One
of them is in the PPC 2.2 tree and the other in the 2.3 tree (both
bitkeeper), I believe.  Did you try both of those?  I'm pretty sure I
fixed this quite thoroughly in one or the other.

2.2 works well for me, but doesn't seem to work for Andrew Fyfe,
according to the comments in 2.3. 2.2 detects my 4M, 2.3 doesn't.

Actually, on closer look, I thought that the 2.3 code was correct.
Could you compare to Andrew's observations in the comment above the
code?  Is he wrong?  I certainly can't see how his comment would be
unless there is a memory scheme he was not detecting, and I do not
think there is.

At least his code and comments are not _entirely_ correct for my
machine. Here's what I've found so far:

- control manages mem in chunks of 2M (a pair of DIMMs), within a
region of 8M in size.
- 2M in bank 1, and 4M, are accessed at offset 0x0.
- 2M in bank 2 are accessed at offset 6M.
- the 2.3 code doesn't detect the mem at 2M in my case. It seems
writing to 0x0 garbles the memory contents at 2M: write to
2M, write to 0x0-garbling 2M, detect 0x0, detect 2M-garbled, so nothing
detected.

I have a bunch of other patches to merge for controlfb anyway, so now
is a good time to straighten this out... with luck and speed we can get
a fix into 2.3.99preX.

I'll speed up then ;-)

The next step is to compile a better detection check, that can detect
mirrored memory regions, so that I can find out what's wrong between
0x0 and 2M..... It's actually very strange, as my 4M do work when
accessed in one block starting at 0x0... so 2M would have to be
different from 0x0 ???

By the way, somewhere I have an alternate OF driver for control, that
IIRC came out of darwin, and it ver accesses VRAM only at 0x0 or 6M....
Unfortunately, it's too big to fit into nvramrc ;-))

Cheers

Michel

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Michel Lanners                 |  " Read Philosophy.  Study Art.
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L-1710 Luxembourg              |
email   mlan@cpu.lu            |
http://www.cpu.lu/~mlan        |                     Learn Always. "

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