Nice oops from agpgart - 2.2 kernels and Alpha

From: Michal Jaegermann (
Date: Fri Oct 13 2000 - 15:38:05 EST

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/ (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,

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(, 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",

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 <>, 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'. :-)

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This archive was generated by hypermail 2b29 : Sun Oct 15 2000 - 21:00:26 EST