[Bug 90963] i915:No display with Display port [drm:intel_dp_start_link_train] *ERROR* too many full retries, give up

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90963

Ander Conselvan de Oliveira <conselvan2 at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #119060|0                           |1
        is obsolete|                            |
 Attachment #119126|0                           |1
        is obsolete|                            |

--- Comment #17 from Ander Conselvan de Oliveira <conselvan2 at gmail.com> ---
Created attachment 119195
  --> https://bugs.freedesktop.org/attachment.cgi?id=119195&action=edit
Fallback to lower link rate on MST link training failure

(In reply to Eong Chen from comment #15)
> Created attachment 119126 [details]
> full dmesg with <Fallback to lower link rate on MST link training> patch
> 
> It shows some crash information. And it doesn't work with my monitor. Sorry
> I didn't read the patch this time. :)

I didn't expect this to fix the problem completely, but to give a clue if the
problem is related to our non-compliant link training implementation.
Unfortunately, there was an error in that patch. Here's a corrected version.

If this produce a line like the following in the log, you can try the patch
below, replacing the number with the one you see in the log, and check if
things work.

[drm:intel_mst_pre_enable_dp] clock recovery succeeded with rate 270000


diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c
b/drivers/gpu/drm/i915/intel_dp_mst.c
index eba5bf9..63fe050 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -57,6 +57,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder
*encoder,
        lane_count = drm_dp_max_lane_count(intel_dp->dpcd);

        rate = intel_dp_max_link_rate(intel_dp);
+       rate = 270000;

        if (intel_dp->num_sink_rates) {
                intel_dp->link_bw = 0;

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