[Bug 75241] radeon_compute_pll_avivo broken in 3.15-rc3

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=75241

Benjamin Herrenschmidt <benh@kernel.crashing.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |benh@kernel.crashing.org

--- Comment #30 from Benjamin Herrenschmidt <benh@kernel.crashing.org> ---
Your latest change broke it for me, sorry for the delay in noticing, that
combination of machine & monitor was stuck in the dark ages for a while...

The combo is Radeon R9 290 (from Sapphire) and good old Apple Cinema Display
23" (1920x1200x60 fixed resolution display) on DVI.

I get a black screen with radeon. It works with Alex's amdgpu. The one liner
that fixes it is in the PLL calculation:

-ref_div_max = max(min(100 / post_div, ref_div_max), 1u);
+ref_div_max = max(min(128 / post_div, ref_div_max), 1u);

I noticed other differences though, the max fb div is 2047 with radeon and 4095
with amdgpu but the above is the key.

This is a trace of amdgpu calculation (which works) after I sprinkled printk's
around:

[    3.471131] fb_div_min/max=4/4095 pll_flags=400
[    3.471132] by 10 ! fb_div_min/max=40/40950
[    3.471133] ref_div_min=2 (from 0/2)
[    3.471133] ref_div_max=1023 (from 0/1023)
[    3.471134] vco_min/max=600000/1200000
[    3.471134] post_div_min/max=4/7
[    3.471135] initial nom=153970, den=2700
[    3.471136] reduced nom=15397, den=270
[    3.471136] - trying post_div 4, ref_div_max=32
[    3.471137]   tentative ref_div=32m, fb_div=7299
[    3.471137]   adjusted ref_div=32m, fb_div=7299
[    3.471138] diff=7, diff_best=-1
[    3.471138] - trying post_div 5, ref_div_max=25
[    3.471139]   tentative ref_div=25m, fb_div=7128
[    3.471139]   adjusted ref_div=25m, fb_div=7128
[    3.471139] diff=6, diff_best=7
[    3.471140] - trying post_div 6, ref_div_max=21
[    3.471140]   tentative ref_div=21m, fb_div=7185
[    3.471141]   adjusted ref_div=21m, fb_div=7185
[    3.471141] diff=6, diff_best=6
[    3.471141] - trying post_div 7, ref_div_max=18
[    3.471142]   tentative ref_div=18m, fb_div=7185
[    3.471142]   adjusted ref_div=18m, fb_div=7185
[    3.471150] diff=6, diff_best=6
[    3.471150] post_div_best=7
[    3.471151] - trying post_div 7, ref_div_max=18
[    3.471151]   tentative ref_div=18m, fb_div=7185
[    3.471152]   adjusted ref_div=18m, fb_div=7185
[    3.471153] [drm:amdgpu_pll_compute] 153970 - 153960, pll dividers - fb:
239.5 ref: 6, post 7

Now this is with radeon *NOTE: I have bumped the max fb div to the same as AMD
GPU when taking that trace but that had no effect:

[    4.718126] fb_div_min/max=4/4095 pll_flags=410
[    4.718126] by 10 ! fb_div_min/max=40/40950
[    4.718127] ref_div_min=2 (from 0/2)
[    4.718128] ref_div_max=1023 (from 0/1023)
[    4.718128] vco_min/max=600000/1200000
[    4.718129] post_div_min/max=4/7
[    4.718129] initial nom=153970, den=2700
[    4.718130] reduced nom=15397, den=270
[    4.718130] - trying post_div 4, ref_div_max=25
[    4.718131]   tentative ref_div=25m, fb_div=5703
[    4.718131]   adjusted ref_div=25m, fb_div=5703
[    4.718132] diff=11, diff_best=-1
[    4.718133] - trying post_div 5, ref_div_max=20
[    4.718133]   tentative ref_div=20m, fb_div=5703
[    4.718133]   adjusted ref_div=20m, fb_div=5703
[    4.718134] diff=11, diff_best=11
[    4.718134] - trying post_div 6, ref_div_max=16
[    4.718135]   tentative ref_div=16m, fb_div=5474
[    4.718135]   adjusted ref_div=16m, fb_div=5474
[    4.718136] diff=14, diff_best=11
[    4.718136] - trying post_div 7, ref_div_max=14
[    4.718136]   tentative ref_div=14m, fb_div=5589
[    4.718137]   adjusted ref_div=14m, fb_div=5589
[    4.718137] diff=12, diff_best=11
[    4.718138] post_div_best=5
[    4.718138] - trying post_div 5, ref_div_max=20
[    4.718139]   tentative ref_div=20m, fb_div=5703
[    4.718139]   adjusted ref_div=20m, fb_div=5703
[    4.718141] [drm:radeon_compute_pll_avivo] 153970 - 153980, pll dividers -
fb: 570.3 ref: 20, post 5

The modeline is:

Modeline 55:"1920x1200" 60 153970 1920 1968 2000 2080 1200 1203 1209 1235 0x48
0x9

And is consistent between the 2 drivers.

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