linux-kernel - drm/i915 KMS regression in Linux 3.16-rc2 (with git bisect result)

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Date:	Wed, 25 Jun 2014 15:03:44 +0200
From:	Tom Van Braeckel <tomvanbraeckel@...il.com>
To:	Daniel Vetter <daniel.vetter@...ll.ch>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>, chris@...is-wilson.co.uk,
	ville.syrjala@...ux.intel.com
Cc:	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: drm/i915 KMS regression in Linux 3.16-rc2 (with git bisect result)

Hi,

There seems to be a regression in the upcoming Linux 3.16-rc2 release
candidate that I bisected down to this first bad commit:
[dbb42748ac4929987c1449ecb296b39ef8956b62] drm/i915: Move the C3 LP
write bit setup to gen3_init_clock_gating() for KMS.

The regression is that during the Ubuntu boot process, the monitor
becomes blank and displays "no signal, going to sleep". This happens
around Kernel Mode Setting time, and does not occur with the
"nomodeset" kernel parameter.

The machine under test is a HP-branded single core Intel Pentium 4 CPU
@ 3.00GHz with this GPU:

00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ
Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller])
        Subsystem: Hewlett-Packard Company Device 3012
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Interrupt: pin A routed to IRQ 16
        Region 0: Memory at e0400000 (32-bit, non-prefetchable) [size=512K]
        Region 1: I/O ports at 10c0 [size=8]
        Region 2: Memory at d0000000 (32-bit, prefetchable) [size=256M]
        Region 3: Memory at e0480000 (32-bit, non-prefetchable) [size=256K]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [90] MSI: Enable- Count=1/1 Maskable- 64bit-
                Address: 00000000  Data: 0000
        Capabilities: [d0] Power Management version 2
                Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
        Kernel driver in use: i915


I confirmed that this regression still exists with the latest version
of Linus' tree.

Kind regards and thanks for all your hard work!

Tom Van Braeckel.

View attachment "dmesg.txt" of type "text/plain" (49514 bytes)

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