| Bug ID | 96789 |
|---|---|
| Summary | Black screen with R9 290 and Apple Cinema Display 23" |
| Product | DRI |
| Version | unspecified |
| Hardware | x86-64 (AMD64) |
| OS | Linux (All) |
| Status | NEW |
| Severity | normal |
| Priority | medium |
| Component | DRM/Radeon |
| Assignee | dri-devel@lists.freedesktop.org |
| Reporter | benh@kernel.crashing.org |
With Radeon (any recent distro version including upstream 4.7-rc5), my Apple
Cinema Display 23" gives a black screen when radeon loads.
The monitor is a fairly old DVI LCD 1920x1200x60. It has a fixed timing, ie, no
scaler. It used to work with earlier versions of radeons but I haven't used it
on a Linux machine for a couple of hears at least.
It works using the agd5f's current amdgpu, but not upstream which doesn't
support the HAWAII. I isolated the difference that makes it work to the PPLL
setting. This one liner fixes it:
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -953,7 +953,7 @@ static void avivo_get_fb_ref_div(unsigned nom, unsigned
den, unsigned post_div,
unsigned *fb_div, unsigned *ref_div)
{
/* limit reference * post divider to a maximum */
- ref_div_max = max(min(100 / post_div, ref_div_max), 1u);
+ ref_div_max = max(min(128 / post_div, ref_div_max), 1u);
/* get matching reference and feedback divider */
*ref_div = min(max(DIV_ROUND_CLOSEST(den, post_div), 1u), ref_div_max);
Here's a log of the working vs. non-working versions of the calculations in
radeon_compute_pll_avivo(). Note that when I did these, I also changed
radeon's max_feedback_div to match amdgpu's value of 0xfff instead of 0x7ff in
current radeon, though that didn't impact the results.
[ 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 (different mode number but same
values).
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