On UP1100 Alpha with an AGP slot and "Advanced Micro Devices [AMD]
AMD-751 [Irongate] System Controller" an attempt to use 'agpgart'
support ends up with an oops. I tried 2.2.17 and 2.2.18pre15 kernels.
With CONFIG_AGP=y and CONFIG_AGP_AMD=y resulting kernel gets stuck
after oops and does not boot.  If CONFIG_AGP=m is used then an attempt
to insert 'agpgart' module ends up with the following oops (after
a run through 'ksymoops'):

ksymoops 2.3.4 on alpha 2.2.18pre15x.  Options used
     -V (default)
     -k /proc/ksyms (default)
     -l /proc/modules (default)
     -o /lib/modules/2.2.18pre15x/ (default)
     -m /boot/System.map-2.2.18pre15x (specified)

Unable to handle kernel paging request at virtual address 0000000062000004
insmod(1048): Oops 1
pc = [<fffffe0000841ba8>]  ra = [<fffffe0000841b7c>]  ps = 0000
Using defaults from ksymoops -t elf64-alpha -a alpha
v0 = 0000000000000000  t0 = 0000000062000000  t1 = 0000000062000000
t2 = 000000000c322000  t3 = fffffc0000802000  t4 = fffffe0000850000
t5 = fffffe0000850000  t6 = fffffffe00000000  t7 = fffffc000c2a0000
s0 = fffffe0000844e50  s1 = fffffe0000844f50  s2 = fffffe0000844cb0
s3 = 0000000000000001  s4 = 0000000000000001  s5 = fffffe0000844e50
s6 = fffffe0000840090  a0 = fffffd01fe000014  a1 = 00000000000000b0
a2 = 0000000000000080  a3 = fffffc0000569310  a4 = fffffc000c2a3d60
a5 = fffffc000c2a3d58  t8 = 0000000000000001  t9 = fffffc0000523078
t10= 0000000000000000  t11= fffffc0000523070  pv = fffffc000031d640
 47f01412  or zero,128,a2
 4441f102  andnot t1,15,t1
 44420401  or t1,t1,t0
 b05e0020  stl t1,32(sp)
 4821f621  zapnot t0,15,t0
 b42a0000  stq t0,0(s1)
 a6090028  ldq a0,40(s0)
Trace: 332014 33bc18 310cf8 42fe80 
Warning (Oops_read): Code line not seen, dumping what data is available

>>PC;  fffffe0000841ba8 <[agpgart]amd_irongate_configure+68/140>   <=====
Trace; 00332014 Before first symbol
Trace; 0033bc18 Before first symbol
Trace; 00310cf8 Before first symbol
Trace; 0042fe80 Before first symbol

1 warning issued.  Results may not be reliable.

followed by a "Segmentation fault" from insmod.  Unfortunately option
-m produces an empty symbol map for the module; also later the module
is not removable with the following output from lsmod:

agpgart                21312   1  (initializing)

This bomb happens on this code

        /* Write out the address of the gatt table */
        OUTREG32(amd_irongate_private.registers, AMD_ATTBASE,
                 agp_bridge.gatt_bus_addr);

from amd_irongate_configure() in drivers/char/agp/agpgart_be.c.
I dropped few printk's there like that:

        /* Get the memory mapped registers */
        pci_read_config_dword(agp_bridge.dev, AMD_MMBASE, &temp);
        printk(KERN_INFO PFX "Read irongate temp %x\n", temp);
        temp = (temp & PCI_BASE_ADDRESS_MEM_MASK);
        printk(KERN_INFO PFX "Masked temp to %x\n", temp);
        amd_irongate_private.registers = (volatile u8 *) ioremap(temp, 4096);
        printk(KERN_INFO PFX "Updated private registers to %x\n",
               amd_irongate_private.registers);

and results are as follows:

Linux agpgart interface v0.99 (c) Jeff Hartmann
agpgart: Maximum main memory to use for agp memory: 204M
agpgart: Detected AMD Irongate chipset
agpgart: Read irongate temp 62000008
agpgart: Masked temp to 62000000
agpgart: Updated private registers to 62000000
Unable to handle kernel paging request at virtual address 0000000062000004

Any ideas what is wrong with this picture?

BTW - despite the following commment in drivers/char/drm/drm.h
"Dec 1999, Richard Henderson <[EMAIL PROTECTED]>, move to generic cmpxchg."
an attempt to compile 'drm' module includes some x86 specific code
from drivers/char/drm/drmP.h, like this:

                __asm__ __volatile__(LOCK_PREFIX "cmpxchgb %b1,%2"
                                     : "=a"(prev)
                                     : "q"(new), "m"(*__xg(ptr)), "0"(old)
                                     : "memory");

and, as you can guess, does not compile on Alpha.  But that is the
next problem after 'agpgart'. :-)

  Michal
  [EMAIL PROTECTED]
  [EMAIL PROTECTED]
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