Bug 99572

Summary: [BXT DP-MST] System hang/crash when plugging in USB typeC DP MST monitor
Product: DRI Reporter: Nathan Ciobanu <nathan.d.ciobanu>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: critical    
Priority: medium CC: intel-gfx-bugs, jim.bride, manasi.d.navare, nathan.d.ciobanu
Version: DRI git   
Hardware: x86-64 (AMD64)   
OS: other   
Whiteboard:
i915 platform: BXT i915 features: display/DP MST
Attachments:
Description Flags
stack trace
none
attachment-9910-0.html none

Description Nathan Ciobanu 2017-01-28 00:40:45 UTC 
Created attachment 129186 [details]
stack trace

Steps to reproduce:
- Connect a 4K DP MST monitor to the USB-C port on a BXT system using a USB-C to DP dongle while the system is up
- Or boot a BXT system with a 4K DP MST monitor attached to the USB-C port using a USB-C to DP dongle

Result:
- The system hangs or reboots immediately.


Notes:

Tentative fix:
https://lists.freedesktop.org/archives/intel-gfx/2017-January/116654.html

Adds the missing INTEL_OUTPUT_DP_MST case in bxt_get_dpll() to correctly
initialize the crtc_state and port plls when link training a DP MST monitor
on BXT/APL devices.
Comment 1 Shawn Lee 2017-01-28 00:45:00 UTC 
Created attachment 129187 [details]
attachment-9910-0.html

Dear sender,

OOO from ww4.5 to ww5.4 for chinese new year. Email response will be slow/delay. Sorry for the inconvenience.

Best regards,
Shawn
Comment 2 Nathan Ciobanu 2017-01-28 01:05:45 UTC 
I added the following check to make sure I trigger a stack trace otherwise the system would reboot without giving me the crash log:

@@ -1862,6 +1863,10 @@ bool bxt_ddi_dp_set_dpll_hw_state(int clock,
        memset(&crtc_state->dpll_hw_state, 0,
               sizeof(crtc_state->dpll_hw_state));

+       if (!memcmp(&zeroes, &dpll_hw_state,
+              sizeof(crtc_state->dpll_hw_state)))
+           BUG();
+
        crtc_state->dpll_hw_state = dpll_hw_state;

        if (encoder->type == INTEL_OUTPUT_DP_MST) {
Comment 3 yann 2017-02-03 12:52:15 UTC 
Reference to Shawn Lee's patch: https://patchwork.freedesktop.org/series/17815/
Comment 4 Jani Nikula 2017-02-03 13:36:12 UTC 
Presumed fixed by

commit 0aab2c721d81590012a5021a516f00666646741f
Author: Lee, Shawn C <shawn.c.lee@intel.com>
Date:   Fri Feb 3 12:32:09 2017 +0800

    drm/i915/bxt: Add MST support when do DPLL calculation

Please reopen if the problem persists with that.

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