[Bug 90039] black screen, X not starting since kernel >=3.15 with Haswell-ULT

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90039

--- Comment #25 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to Ander Conselvan de Oliveira from comment #23)
> (In reply to Chris Wilson from comment #21)
> > (In reply to Ander Conselvan de Oliveira from comment #18)
> > > Looking at your dmesg, it seems X turns off all CRTCs (which is normal
> > > behavior).  The odd part is that after that no CRTCs are turned on.
> > 
> > It's not X that is turning them off, the kernel reports all outputs as
> > unknown status, including the one currently active.
> 
> What I saw is:
> 
> [   34.584653] [drm:drm_ioctl] pid=1987, dev=0xe200, auth=1,
> DRM_IOCTL_MODE_SETCRTC
> [   34.584663] [drm:drm_mode_setcrtc] [CRTC:20]
> [   34.584667] [drm:intel_crtc_set_config] [CRTC:20] [NOFB]
> 
> ...
> 
> [   34.854489] [drm:drm_ioctl] pid=1987, dev=0xe200, auth=1,
> DRM_IOCTL_MODE_SETCRTC
> [   34.854493] [drm:drm_mode_setcrtc] [CRTC:24]
> [   34.854495] [drm:intel_crtc_set_config] [CRTC:24] [NOFB]

which is not present in the last dmesg, which appears to just contain X
startup.

> [   34.854505] [drm:drm_ioctl] pid=1987, dev=0xe200, auth=1,
> DRM_IOCTL_MODE_SETCRTC
> [   34.854508] [drm:drm_mode_setcrtc] [CRTC:28]
> [   34.854510] [drm:intel_crtc_set_config] [CRTC:28] [NOFB]
> 
> I might have missed something, but that seems consistent with X behavior to
> me. 

X only disables CRTC that have mismatching kernel state as X tries to use
whatever mode and configuration the kernel reports. This set of disabling is
from after X initialisation.

> Before those SetCrtc calls, I see:
> 
> [   34.075768] [drm:drm_mode_getconnector] [CONNECTOR:31:?]
> [   34.075770] [drm:drm_helper_probe_single_connector_modes_merge_bits]
> [CONNECTOR:31:eDP-1]
> [   34.075772] [drm:intel_dp_detect] [CONNECTOR:31:eDP-1]
> [   34.075777] [drm:drm_helper_probe_single_connector_modes_merge_bits]
> [CONNECTOR:31:eDP-1] status updated from 3 to 1
> [   34.075787] [drm:drm_add_display_info] eDP-1: Assigning EDID-1.4 digital
> sink color depth as 6 bpc.
> [   34.075788] [drm:drm_edid_to_eld] ELD: no CEA Extension found
> [   34.075791] [drm:drm_helper_probe_single_connector_modes_merge_bits]
> [CONNECTOR:31:eDP-1] probed modes :
> [   34.075795] [drm:drm_mode_debug_printmodeline] Modeline 32:"1920x1080" 60
> 138700 1920 1968 2000 2080 1080 1083 1088 1111 0x48 0xa
> 
> And I see this in drm_crtc.h
> 
> enum drm_connector_status {
>         connector_status_connected = 1,
>         connector_status_disconnected = 2,
>         connector_status_unknown = 3,
> };
> 
> So it seems connector status changed from disconnected (3) to (1). Did I
> miss something?

unknown -> connected and implies that no active mode was found during the
initial probe.

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