Mine

Breakpoint 1, radeon_in_pll (radeon=0xbff1b600, offset=0) at radeontool.c:215
215             radeon_set(radeon, RADEON_CLOCK_CNTL_INDEX, offset & 0x3f);
(gdb) s
radeon_set (radeon=0xbff1b600, offset=8, value=0) at radeontool.c:142
142             if (radeon->mmio_mem == NULL) {
(gdb) s
153             *(unsigned int * volatile)(radeon->mmio_mem + offset) = value;  
(gdb) s
155     }