[Intel-gfx] i915 / 3.15 intermittently boots into blank screeen

[Daniel Vetter]

On Wed, Jul 30, 2014 at 12:01:38AM +0200, Jan Niggemann wrote:
> Am 29.07.2014 23:35, schrieb Daniel Vetter:
> >On Tue, Jul 29, 2014 at 11:09 PM, Jan Niggemann <jn at hz6.de> wrote:
> >>Am 18.07.2014 18:25, schrieb Daniel Vetter:
> >>>
> >>>On Fri, Jul 18, 2014 at 4:49 PM, Jan Niggemann <jn at hz6.de> wrote:
> >>>
> >>>>
> >>>>Am 18.07.2014 15:27, schrieb Daniel Vetter:
> >>>>>
> >>>>>
> >>>>>On Thu, Jul 17, 2014 at 10:31:30PM +0200, Jan Niggemann wrote:
> >>>>>>
> >>>>>>
> >>>>>>I'm experiencing an issue with 3.15.5 on my Lenovo T400:
> >>>>>>Since 3.15 (or 3.14, can't say for sure), the boot starts
> >>>>>>normally, but
> >>>>>>the
> >>>>>>first mode change doesn't occur, resulting in a black screen
> >>>>>>with
> >>>>>>backlight
> >>>>>>on. The system is entirely unresponsive and I can only press the
> >>>>>>power
> >>>>>>button until to switch it off.
> >>>>>
> >>>>>
> >>>>>I think the only way to move forward here is to double-check that
> >>>>>3.14
> >>>>>
> >>>>>works and 3.15 is broken by recompiling with the same .config
> >>>>>(occasionally config changes cause regressions). And then do a
> >>>>>full git
> >>>>>bisect to find the offending commit.
> >>>>
> >>>>
> >>>>thank you for the feedback.
> >>>>I still have all my custom built kernels, I will test 3.14.0 through
> >>>>3.14.8
> >>>>to make sure those were OK and report back.
> >>>
> >>>
> >>>You only need to test 3.14.0, since the backported fixes only contain
> >>>a very small subset of all patches for 3.15. So it's more efficient to
> >>>then switch to git bisect between 3.14 and 3.15 directly (after you've
> >>>confirmed that 3.15.0 is indeed busted).
> >>
> >>I familiarized with git bisect, that was something I had never used
> >>before.
> >>
> >>I started it with "git bisect start v3.15 v3.14 -- drivers/gpu/drm/i915"
> >>
> >>This lead me to this:
> >>
> >>cfa7c862982b431add7f2b362526bf31372fc7b0 is the first bad commit
> >>commit cfa7c862982b431add7f2b362526bf31372fc7b0
> >>Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> >>Date:   Tue Apr 29 11:53:58 2014 +0200
> >>
> >>    drm/i915: Sanitize the enable_ppgtt module option once
> >>
> >>    Otherwise we'll end up spamming dmesg on every context creation on
> >>snb
> >>    with vt-d enabled. This regression was introduced in
> >>
> >>    commit 246cbfb5fb9a1ca0997fbb135464c1ff5bb9c549
> >>    Author: Ben Widawsky <benjamin.widawsky at intel.com>
> >>    Date:   Fri Dec 6 14:11:14 2013 -0800
> >>
> >>        drm/i915: Reorganize intel_enable_ppgtt
> >>
> >>    As the i915.enable_ppgtt is read-only it cannot be changed after the
> >>    module is loaded and so we can perform an early sanitization of the
> >>    values.
> >>
> >>    v2:
> >>    - Add comment and pimp commit message (Chris)
> >>    - Use the param consistently (Jani)
> >>
> >>    v3:
> >>    - Fix init sequence on pre-gen6 by moving the sanitize_ppgtt call to
> >>      gtt_init. Fixes boot hangs on pre-gen6.
> >>    - Add a debug output for the sanitize ppgtt mode.
> >>
> >>    References: https://lkml.org/lkml/2014/4/17/599
> >>    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77916
> >>    Cc: Alessandro Suardi <alessandro.suardi at gmail.com>
> >>    Cc: Ben Widawsky <ben at bwidawsk.net>
> >>    Cc: Chris Wilson <chris at chris-wilson.co.uk>
> >>    Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> >>    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> >>    Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> >>
> >>:040000 040000 5488e397a1aaa28dca4a252452e9463b0a8f8d10
> >>214c8e98b3c72844e48ab7aef02cba7daf139fab M      drivers
> >>
> >>I realized that the issue does always show, contrary to the subject
> >>initially chosen.
> >>
> >>Unfortunately I can't say anything else, but maybe this will help you
> >>experts spot the issue.
> >>If I can help more, be it with testing or anything else, just let me
> >>know.
> >
> >Hm, I'm not aware of this breaking any gm45 machines, mine here is
> >still happy. Can you please make sure that you don't have any i915
> >module options set anywhere, either on the kernel cmdline, modeprobe
> >config files in /etc or anywhere else?
> My kernel cmdline doesn't have anything, but /etc/modprobe.d/i915-kms.conf
> exists. Its content is this single line: options i915 modeset=1
> Can't remember if I created that (it's from 2010) or if it's Debian
> default...
> grep -Ri i915 /etc/ doesn't show anything else.
> 
> grep 915 config-3.15
> CONFIG_DRM_I915=m
> CONFIG_DRM_I915_KMS=y
> CONFIG_DRM_I915_FBDEV=y
> # CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT is not set
> # CONFIG_DRM_I915_UMS is not set
> CONFIG_SND_HDA_I915=y
> 
> Would it help if I included the driver instead of building a module?

Shouldn't change anything really, and config all looks sane. Can you
please retest with latest upstream (3.16 or even drm-intel-nightly)?

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch