Mach64 GX driver problems in post 2.4.22 kernels

Hi,

I have the following problem when I try to build a new kernel for my  
PowerMac 7500 (604e CPU, PCI adapters: Adaptec 2940UW SCSI, Apple  
Mach64 GX card):

Kernel versions newer than my last build (of 2.4.22 plus preempt, benh,  
lowlatency, ea+acl+nfsacl, cryptoloop patches, all from debian sid  
source packages of that time) show a blank screen when switching to the  
Mach64 framebuffer (BootX pre-boot messages are fine). The kernel  
continues to boot and even activates the atyfb driver so I can login  
blind on the console or remotely via ssh.

I have so far built the following kernels: 2.4.25 from debian package  
kernel-source-2.4.25_2.4.25-3, with and without the debian kernel- 
patch-2.4.25-powerpc patch derived from Benjamin Herrenschmidt's source  
tree, a kernel from each of www.kernel.org 2.4.26 and 2.4.25 archives  
(without any patches) and a downloaded kernel from Benjamin's site  
directly (rsync'ed on 2004/06/01, ca. 16:30). All of these builds show  
the behaviour outlined above: kernel boots fine but screen blanks  
immediatly.

As Mach64 is obviously quite important to a number of PowerMacs I hope  
someone already stumbled across the same problem, although I couldn't  
find anything truely specific by googling.

Please tell if you need any more specific logs or info, I'll include  
the dmesg lines and lspci -v output relevant to the card for a start:

dmesg | grep -i \(aty\|console\)

Kernel command line: root=/dev/sda7 video=atyfb:vmode:18:cmode:8  
panic=60
Console: colour dummy device 80x25
atyfb: mach64GX (ATI888GX00) [0x00d7 rev 0x03] 4M VRAM, 14.31818 MHz  
XTAL, 135
MHz PLL, 50 Mhz MCLK
Console: switching to colour frame buffer device 144x54
fb0: ATY Mach64 frame buffer device on PCI
MacOS display is /bandit/ATY,mach64

I noticed one of these lines reads differently on my 2.4.22 kernel:

atyfb: mach64GX (ATI888GX00) [0x00d7 rev 0x03] 4M VRAM, 14.31818 MHz
XTAL, 135 MHz PLL, 50 Mhz MCLK
                   ^^^^^^^^^^^
Would that be a sign of the culprit?

lspci -v -s 00:0f.0

0000:00:0f.0 VGA compatible controller: ATI Technologies Inc 210888GX  
[Mach64
GX] (rev 03) (prog-if 00 [VGA])
       Flags: stepping, medium devsel, IRQ 25
       Memory at 81000000 (32-bit, non-prefetchable) [size=16M]
       Expansion ROM at <unassigned> [disabled] [size=64K]



Thanks for any input you can provide with respect to my problem.

Ciao, Thomas Jahns
-- 
"Computers are good at following instructions,
 but not at reading your mind."
D. E. Knuth, The TeXbook, Addison-Wesley 1984, 1986, 1996, p. 9


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