[Bug 75211] Division error in radeon_compute_pll_avivo (X hang)

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=75211

--- Comment #7 from Darren Salt <bugspam@moreofthesa.me.uk> ---
Can't do that (radeon module is built in, and no debug symbols – should switch
that on), but ksymoops output (below) is clear enough for me to determine that
the marked line is where the bug makes itself known:

                 if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {
                        vco_min *= 10;
                        vco_max *= 10;
                }

/* here */      post_div_min = vco_min / target_clock;
                if ((target_clock * post_div_min) < vco_min)
                        ++post_div_min;
                if (post_div_min < pll->min_post_div)    
                        post_div_min = pll->min_post_div;

Which means that target_clock is zero, which means that freq is 0 or freq/10 is
0.


>>RIP; ffffffff812513d0 <radeon_compute_pll_avivo+b6/324>   <=====

>>RAX; 00000000000927c0 <__per_cpu_end+804c0/fedd00>
>>RBX; ffff880236dc8210 <phys_startup_64+ffff880235dc8210/ffffffff80000000>
>>RCX; 0000000000124f80 <__per_cpu_end+112c80/fedd00>
>>RSI; 00000000000927c0 <__per_cpu_end+804c0/fedd00>
>>RBP; ffff8800bd6d2c00 <phys_startup_64+ffff8800bc6d2c00/ffffffff80000000>
>>R08; ffff88021b08fb08 <phys_startup_64+ffff88021a08fb08/ffffffff80000000>
>>R09; ffff88021b08fb00 <phys_startup_64+ffff88021a08fb00/ffffffff80000000>
>>R12; ffff880236dc8000 <phys_startup_64+ffff880235dc8000/ffffffff80000000>
>>R14; 0000000000004ff6 <exception_stacks+ff6/6000>

Trace; ffffffff81227da9 <drm_detect_hdmi_monitor+54/69>
Trace; ffffffff8123ed95 <atombios_crtc_mode_set+100/593>
Trace; ffffffff812d6725 <class_dev_iter_next+c/33>
Trace; ffffffff812d68ed <class_for_each_device+8a/9f>
Trace; ffffffff81213ccd <drm_crtc_helper_set_mode+2a3/424>
Trace; ffffffff812145a5 <drm_crtc_helper_set_config+601/853>
Trace; ffffffff81250650 <radeon_crtc_set_config+3e/d9>
Trace; ffffffff81222183 <drm_mode_set_config_internal+48/c0>
Trace; ffffffff81224843 <drm_mode_setcrtc+3d3/487>
Trace; ffffffff81250dac <radeon_crtc_load_lut+275/630>
Trace; ffffffff81219f06 <drm_ioctl+337/3a6>
Trace; ffffffff81224470 <drm_mode_setcrtc+0/487>
Trace; ffffffff81468fcc <_raw_spin_unlock_irqrestore+f/21>
Trace; ffffffff81234864 <radeon_drm_ioctl+42/6e>
Trace; ffffffff810b10a7 <do_vfs_ioctl+356/420>
Trace; ffffffff810b8747 <__fget+64/6c>
Trace; ffffffff810b11a4 <sys_ioctl+33/58>
Trace; ffffffff81469ca6 <system_call_fastpath+1a/1f>

Code;  ffffffff812513a5 <radeon_compute_pll_avivo+8b/324>
0000000000000000 <_RIP>:
Code;  ffffffff812513a5 <radeon_compute_pll_avivo+8b/324>
   0:   09 8b 6b 08 89 6c         or     %ecx,0x6c89086b(%rbx)
Code;  ffffffff812513ab <radeon_compute_pll_avivo+91/324>
   6:   24 20                     and    $0x20,%al
Code;  ffffffff812513ad <radeon_compute_pll_avivo+93/324>
   8:   eb 5f                     jmp    69 <_RIP+0x69>
Code;  ffffffff812513af <radeon_compute_pll_avivo+95/324>
   a:   80 e5 20                  and    $0x20,%ch
Code;  ffffffff812513b2 <radeon_compute_pll_avivo+98/324>
   d:   74 08                     je     17 <_RIP+0x17>
Code;  ffffffff812513b4 <radeon_compute_pll_avivo+9a/324>
   f:   8b 73 1c                  mov    0x1c(%rbx),%esi
Code;  ffffffff812513b7 <radeon_compute_pll_avivo+9d/324>
  12:   8b 4b 20                  mov    0x20(%rbx),%ecx
Code;  ffffffff812513ba <radeon_compute_pll_avivo+a0/324>
  15:   eb 06                     jmp    1d <_RIP+0x1d>
Code;  ffffffff812513bc <radeon_compute_pll_avivo+a2/324>
  17:   8b 73 14                  mov    0x14(%rbx),%esi
Code;  ffffffff812513bf <radeon_compute_pll_avivo+a5/324>
  1a:   8b 4b 18                  mov    0x18(%rbx),%ecx
Code;  ffffffff812513c2 <radeon_compute_pll_avivo+a8/324>
  1d:   85 ff                     test   %edi,%edi
Code;  ffffffff812513c4 <radeon_compute_pll_avivo+aa/324>
  1f:   74 06                     je     27 <_RIP+0x27>
Code;  ffffffff812513c6 <radeon_compute_pll_avivo+ac/324>
  21:   6b f6 0a                  imul   $0xa,%esi,%esi
Code;  ffffffff812513c9 <radeon_compute_pll_avivo+af/324>
  24:   6b c9 0a                  imul   $0xa,%ecx,%ecx
Code;  ffffffff812513cc <radeon_compute_pll_avivo+b2/324>
  27:   31 d2                     xor    %edx,%edx
Code;  ffffffff812513ce <radeon_compute_pll_avivo+b4/324>
  29:   89 f0                     mov    %esi,%eax
Code;  ffffffff812513d0 <radeon_compute_pll_avivo+b6/324>   <=====
  2b:   41 f7 f5                  div    %r13d   <=====
Code;  ffffffff812513d3 <radeon_compute_pll_avivo+b9/324>
  2e:   89 c2                     mov    %eax,%edx
Code;  ffffffff812513d5 <radeon_compute_pll_avivo+bb/324>
  30:   8d 68 01                  lea    0x1(%rax),%ebp
Code;  ffffffff812513d8 <radeon_compute_pll_avivo+be/324>
  33:   41 0f af d5               imul   %r13d,%edx
Code;  ffffffff812513dc <radeon_compute_pll_avivo+c2/324>
  37:   39 f2                     cmp    %esi,%edx
Code;  ffffffff812513de <radeon_compute_pll_avivo+c4/324>
  39:   8b 53 30                  mov    0x30(%rbx),%edx
Code;  ffffffff812513e1 <radeon_compute_pll_avivo+c7/324>
  3c:   0f 43 e8                  cmovae %eax,%ebp
Code;  ffffffff812513e4 <radeon_compute_pll_avivo+ca/324>
  3f:   89                        .byte 0x89

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