[Bug 40699] KMS on Thinkpad W500: no picture on external monitors with DisplayPort, but DVI works.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=40699

Maciej Pawlik <maciej.pawlik.xml at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maciej.pawlik.xml at gmail.com

--- Comment #2 from Maciej Pawlik <maciej.pawlik.xml at gmail.com> ---
Hi,

I have the same issue on W500 and radeon hd3650 (or firegl v5700) RV635/M86
chip with dell u2412m monitor. Monitor complains that it cannot sync with
signal from DP.
I was able to do a bisect of vanilla kernel, and this problem was introduced
here:

git bisect start
# bad: [fb9a90f7c674f3ddef6baf55cb1612dadd8ea752] Merge remote branch
'airlied/drm-core-next' into tmp
git bisect bad fb9a90f7c674f3ddef6baf55cb1612dadd8ea752
# good: [42311ff90dc8746bd81427b2ed6efda9af791b77] drm/ttm: introduce utility
function to free an allocated memory node
git bisect good 42311ff90dc8746bd81427b2ed6efda9af791b77
# good: [63847e66b28ed5e0dc28409d767e8f3891502ac4] Merge branch 'idle-release'
of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6
git bisect good 63847e66b28ed5e0dc28409d767e8f3891502ac4
# good: [53b2087d218c100657bddcb8ae887fa07862fb81] drm/i915: fix debugging
compilation error from previous commit
git bisect good 53b2087d218c100657bddcb8ae887fa07862fb81
# good: [1bbee7d616d5fdffa6c1c86075dbffe2b3e236ea] Merge branch
'upstream-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid
git bisect good 1bbee7d616d5fdffa6c1c86075dbffe2b3e236ea
# good: [96a03fce54af40b4f0820cd729608bc32c9b8949] Merge branch 'drm-kdb-next'
into drm-core-next
git bisect good 96a03fce54af40b4f0820cd729608bc32c9b8949
# bad: [8088699f029b2a27af9bc5431ef7542c84195760] drm/i915: don't program FDI
RX/TX in mode_set
git bisect bad 8088699f029b2a27af9bc5431ef7542c84195760
# bad: [e59f2bac15042eb744851bcf866f18dadc3091c6] drm/i915: Wait for pending
flips on the GPU
git bisect bad e59f2bac15042eb744851bcf866f18dadc3091c6
# good: [f28488c282d8916b9b6190cc41714815bbaf97d5] drm/radeon/kms: remove some
pll algo flags
git bisect good f28488c282d8916b9b6190cc41714815bbaf97d5
# bad: [75fa0b08e50cb72715b58321e8259c47adfe4c6f] drm/radeon: Modify
radeon_pm_in_vbl to use radeon_get_crtc_scanoutpos()
git bisect bad 75fa0b08e50cb72715b58321e8259c47adfe4c6f
# bad: [ba032a58d1f320039e7850fb6e8651695c1aa571] drm/radeon/kms: rework spread
spectrum handling
git bisect bad ba032a58d1f320039e7850fb6e8651695c1aa571
# good: [48dfaaeb6637240af3089bf9b7a00a6cf24e0182] drm/radeon/kms: remove new
pll algo
git bisect good 48dfaaeb6637240af3089bf9b7a00a6cf24e0182
# first bad commit: [ba032a58d1f320039e7850fb6e8651695c1aa571] drm/radeon/kms:
rework spread spectrum handling

So it's probably related to spread spectrum handling on displayport, which was
introduced in that commit. I've done some tinkering with current kernel 3.12.6,
and a simple change (this probably disables spread spectrum on DP) made my DP
monitor work:

laptok linux # diff -ruN drivers/gpu/drm/radeon/atombios_crtc.c
~/atombios_crtc.c.original
--- drivers/gpu/drm/radeon/atombios_crtc.c      2014-01-13 21:46:29.000000000
+0100
+++ /root/atombios_crtc.c.original      2014-01-13 20:59:30.000000000 +0100
@@ -938,13 +938,11 @@
                                                       
radeon_atombios_get_ppll_ss_info(rdev,
                                                                               
         &radeon_crtc->ss,
                                                                               
         ATOM_DP_SS_ID1);
-                               } else {}
-                               /*
+                               } else
                                        radeon_crtc->ss_enabled =
                                               
radeon_atombios_get_ppll_ss_info(rdev,
                                                                               
 &radeon_crtc->ss,
                                                                               
 ATOM_DP_SS_ID1);
-                                                                              
 */
                        }
                        break;
                case ATOM_ENCODER_MODE_LVDS:

If there is anything more I can do please do let me know.

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