Bug 97290 - Commit "drm/i915/gen9: Give one extra block per line for SKL plane WM calculations" breaks multi monitor setup
Summary: Commit "drm/i915/gen9: Give one extra block per line for SKL plane WM calcula...
Status: CLOSED FIXED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Intel (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: medium major
Assignee: Intel GFX Bugs mailing list
QA Contact: Intel GFX Bugs mailing list
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-08-11 08:12 UTC by Kim Lidström
Modified: 2016-08-26 08:04 UTC (History)
1 user (show)

See Also:
i915 platform: SKL
i915 features: display/DP

Attachments
Picture that shows the symptoms (452.25 KB, image/jpeg)
2016-08-11 08:12 UTC, Kim Lidström 		no flags Details
dmesg (450.49 KB, text/plain)
2016-08-11 08:14 UTC, Kim Lidström 		no flags Details
Patch that makes everything work again (707 bytes, text/plain)
2016-08-11 08:17 UTC, Kim Lidström 		no flags Details
View All

Description Kim Lidström 2016-08-11 08:12:25 UTC 
Created attachment 125691 [details]
Picture that shows the symptoms

After commit 055c3ff69d440928964228455ec29b071258d5fa my multi monitor setup breaks.
I simply cannot get any output on the external monitors on my Thinkpad X260 (Connected to a docking station) whatsoever and nothing in particular shows up in dmesg.

I attached a picture I took with my camera to show demonstrate the symptom.

Reverting the commit makes everything work as intended again.
Comment 1 Kim Lidström 2016-08-11 08:14:57 UTC 
Created attachment 125692 [details]
dmesg

Attaching a dmesg right after I have booted, started X and tried running xrandr.
Comment 2 Kim Lidström 2016-08-11 08:17:16 UTC 
Created attachment 125693 [details]
Patch that makes everything work again

I am successfully running the latest nightly with this patch applied.
Comment 3 Kim Lidström 2016-08-11 08:18:38 UTC 
The xrandr line I am running is:

xrandr --output VIRTUAL1 --off --output eDP1 --mode 1920x1080 --pos 3120x632 --rotate normal --output DP1 --off --output DP2-1 --primary --mode 1920x1200 --pos 0x632 --rotate normal --output DP2-2 --mode 1920x1200 --pos 1920x0 --rotate right --output DP2-3 --off --output HDMI2 --off --output HDMI1 --off --output DP2 --off
Comment 4 Kim Lidström 2016-08-11 08:21:29 UTC 
I missed a slight detail.

I don't get any X output on the external monitors.

Sorry about that.
Comment 5 Kim Lidström 2016-08-11 08:28:19 UTC 
Comment on attachment 125693 [details]
Patch that makes everything work again

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 99014d7..1438a4b 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3352,8 +3352,6 @@ static uint32_t skl_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
                plane_bytes_per_line *= 4;
                plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
                plane_blocks_per_line /= 4;
-       } else if (tiling == DRM_FORMAT_MOD_NONE) {
-               plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512) + 1;
        } else {
                plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
        }
Comment 6 Kim Lidström 2016-08-11 08:30:00 UTC 
I made a boo-boo with a patch. That is the correct one.
Comment 7 Joonas Lahtinen 2016-08-11 08:31:01 UTC 
So basically, reverting the following patch helps;

commit 58e311b09c319183254d9220c50a533e7157c9ab
Author: Matt Roper <matthew.d.roper@intel.com>
Date:   Thu Aug 4 14:08:00 2016 -0700

    drm/i915/gen9: Give one extra block per line for SKL plane WM calculations
Comment 8 Kim Lidström 2016-08-25 19:14:56 UTC 
It works with the latest nightly now.

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