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Date: Fri, 10 Aug 2012 14:35:13 +0200
From: Daniel Vetter <daniel.vetter@...ll.ch>
To: Takashi Iwai <tiwai@...e.de>
Cc: Hugh Dickins <hughd@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Chris Wilson <chris@...is-wilson.co.uk>,
Giacomo Comes <comes@...c.edu>,
Paulo Zanoni <paulo.r.zanoni@...el.com>,
linux-kernel@...r.kernel.org
Subject: Re: i915 regression on 3.6-rc1: lid blanks screen
On Fri, Aug 10, 2012 at 1:59 PM, Takashi Iwai <tiwai@...e.de> wrote:
> At Mon, 6 Aug 2012 11:25:30 -0700 (PDT),
> Hugh Dickins wrote:
>>
>> On Mon, 6 Aug 2012, Daniel Vetter wrote:
>> > On Mon, Aug 6, 2012 at 6:21 AM, Hugh Dickins <hughd@...gle.com> wrote:
>> > > On Sun, 5 Aug 2012, Takashi Iwai wrote:
>> > >> At Sat, 4 Aug 2012 10:01:13 -0700 (PDT),
>> > >> Hugh Dickins wrote:
>> > >> >
>> > >> > Sorry to report that with 3.6-rc1, closing and opening the lid on
>> > >> > this ThinkPad T420s leaves the screen blank, and I have to reboot.
>> > >> >
>> > >> > Bisection led to this commit, and reverting indeed gets my screen back:
>> > >> >
>> > >> > commit 520c41cf2fa029d1e8b923ac2026f96664f17c4b
>> > >> > Author: Daniel Vetter <daniel.vetter@...ll.ch>
>> > >> > Date: Wed Jul 11 16:27:52 2012 +0200
>> > >> >
>> > >> > drm/i915/lvds: ditch ->prepare special case
>> > > ...
>> > >>
>> > >> Hm, it's surprising.
>> > >>
>> > >> Could you check whether the counter-part intel_lvds_enable() is
>> > >> called? If the prepare callback affects, it must be from the mode
>> > >> setting (drm_crtc_helper_set_mode()).
>> > >
>> > > Yes, I put a dump_stack() in both, and intel_lvds_enable() gets called
>> > > about 0.28 seconds after the intel_lvds_disable() when I lift the lid;
>> > > but with no video display until I revert that commit.
>> >
>> > Can you please boot with drm.debug=0xe added to your kernel cmdline,
>> > reproduce the issue (with the two dump_stack calls added) and then
>> > attach the full dmesg?
>>
>> Collected, I'll send it to you both privately in a moment.
>>
>> >
>> > Also a few other things to try: What happens if you do a modeset on
>> > the LVDS while it's still working, e.g.
>>
>> In the dmesg, I've only gone to runlevel 3, simply working on the
>> console without startx. For these xrandrs to work, I did startx
>> and used the graphics screen.
>
> OK, now I can see the problem here, too. The key is that it happens
> only on Linux console, not on X. That's why no one else reported.
> I guess the problem can be seen on many laptops with LVDS on PCH.
>
> Looking at intel_reg_dumper output, BLC_PWM_CPU_CTL is 0 while other
> registers are set correctly. This seems coming from the rewrite of
> backlight control code by commit
> 24ded204: drm/i915: properly enable the blc controller on the right pipe
> and
> a4f32fc3: drm/i915: don't forget the PCH backlight registers
>
> While the latter fixes the regression by the former commit, it still
> doesn't cover this regression.
>
> I don't know the exact hardware behavior, but it looks like that
> resetting BLC_PWM_PCH_CTL2 and BLC_PWM_PCH_CTL1 clears the
> BLC_PWM_CPU_CTL (oh what confusing reg names).
>
> FWIW, the commit 520c41cf you mentioned is no direct cause. This
> patch works fine on the top of 3.5 kernel. But it's like a bad drug,
> the combination of this and other two commits break things.
>
> The patch below is my quick fix. It worked on an HP laptop.
> Hugh, could you give it a try?
Hm, this sounds eerily familiar to the backlight bug you've recently fixed in
commit 6db65cbb941f9d433659bdad02b307f6d94465df
Author: Takashi Iwai <tiwai@...e.de>
Date: Thu Jun 21 15:30:41 2012 +0200
drm/i915: Fix eDP blank screen after S3 resume on HP desktops
Have you checked other code-paths for such issues? The resume code
seems to follow this order already ... also, when you submit this
patch, can you please add a small comment to explain the ordering
constraint, like in the resume register restore function?
Thanks, Daniel
>
>
> thanks,
>
> Takashi
>
> ===
> From: Takashi Iwai <tiwai@...e.de>
> Subject: [PATCH] drm/i915: Fix blank panel at reopening lid on Linux console
>
> When you reopen the lid on Linux console on a laptop with PCH, the
> panel suddenly goes blank. It seems because BLC_PWM_CPU_CTL register
> is cleared when BLC_PWM_PCH_CTL1 and BLC_PWM_PCH_CTL2 registers are
> played.
>
> This patch fixes the problem by setting BLC_PWM_CPU_CTL after enabling
> BLC_PWM_PCH_CTL_1 and _2 registers.
>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
> drivers/gpu/drm/i915/intel_panel.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 10c7d39..d640425 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -311,9 +311,6 @@ void intel_panel_enable_backlight(struct drm_device *dev,
> if (dev_priv->backlight_level == 0)
> dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
>
> - dev_priv->backlight_enabled = true;
> - intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
> -
> if (INTEL_INFO(dev)->gen >= 4) {
> uint32_t reg, tmp;
>
> @@ -326,7 +323,7 @@ void intel_panel_enable_backlight(struct drm_device *dev,
> * we don't track the backlight dpms state, hence check whether
> * we have to do anything first. */
> if (tmp & BLM_PWM_ENABLE)
> - return;
> + goto set_level;
>
> if (dev_priv->num_pipe == 3)
> tmp &= ~BLM_PIPE_SELECT_IVB;
> @@ -347,6 +344,10 @@ void intel_panel_enable_backlight(struct drm_device *dev,
> I915_WRITE(BLC_PWM_PCH_CTL1, tmp);
> }
> }
> +
> +set_level:
> + dev_priv->backlight_enabled = true;
> + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
> }
>
> static void intel_panel_init_backlight(struct drm_device *dev)
> --
> 1.7.11.4
>
--
Daniel Vetter
daniel.vetter@...ll.ch - +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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