Hello all,
I'm porting linux for a board with a R4KECr2. So far I was using
CONFIG_CPU_MIPS32_R1 and the kernel (2.6.14) was running well.
But I'm unable to get it working with CONFIG_CPU_MIPS32_R2, it freezes
somewhere in trap_init, more exactly in r4k_flush_icache_range().
Here is a snippet from the generated assembly code:
00002624 <r4k_flush_icache_range>:
2624: 27bdffd0 addiu sp,sp,-48
2628: 3c020000 lui v0,0x0
262c: afb30024 sw s3,36(sp)
2630: afb20020 sw s2,32(sp)
2634: afbf0028 sw ra,40(sp)
2638: afb1001c sw s1,28(sp)
263c: afb00018 sw s0,24(sp)
[...]
26a0: bc900000 cache 0x10,0(a0)
26a4: 1464fffd bne v1,a0,269c <r4k_flush_icache_range+0x78>
26a8: 3c020000 lui v0,0x0
26ac: 2442277c addiu v0,v0,10108 <----------
26b0: 00400408 jr.hb v0
26b4: 00000000 nop
[...]
272c: 8c43000c lw v1,12(v0)
2730: 0060f809 jalr v1
2734: 00000000 nop
2738: 3c020000 lui v0,0x0
273c: 2442277c addiu v0,v0,10108 <----------
2740: 00400408 jr.hb v0
2744: 00000000 nop
2748: 8fbf0028 lw ra,40(sp)
274c: 8fb30024 lw s3,36(sp)
2750: 8fb20020 lw s2,32(sp)
2754: 8fb1001c lw s1,28(sp)
2758: 8fb00018 lw s0,24(sp)
275c: 03e00008 jr ra
2760: 27bd0030 addiu sp,sp,48
2764: 3c020000 lui v0,0x0
2768: 8c430018 lw v1,24(v0)
276c: 0060f809 jalr v1
2770: 00000000 nop
2774: 0800099c j 2670 <r4k_flush_icache_range+0x4c>
2778: 3c030000 lui v1,0x0
0000277c <r4k_dma_cache_inv>:
[...]
At offset 0x26ac and 0x273c, we can see that instruction_hazard() got
duplicated due to inlining, and that the jr.hb is going to send us to
10108 (0x277C), outside the function...
The only way I managed to get a good value in v0 was by using -O0 and
making r4k_flush_icache_range return int.
Now I'm really not familiar with gcc inline assembly so I don't know if
this is a compiler bug or if something is missing in
instruction_hazard().
# mipsel-linux-gcc -v
Using built-in specs.
Target: mipsel-linux-uclibc
Configured
with: /home/work/buildroot/toolchain_build_mipsel/gcc-4.0.2/configure
--prefix=/opt/toolchains/mipsel-uclibc-0.9.28-gcc-4.0.2
--build=i386-pc-linux-gnu --host=i386-pc-linux-gnu
--target=mipsel-linux-uclibc --enable-languages=c,c++ --enable-shared
--disable-__cxa_atexit --enable-target-optspace --with-gnu-ld
--disable-nls --enable-threads --enable-multilib
Thread model: posix
gcc version 4.0.2
#
Thanks,
--
Maxime
