Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Daniel Vetter]

Another regression for Jairo to track.
-Daniel

On Thu, Sep 24, 2015 at 05:22:09PM -0400, Nick Bowler wrote:
> Hi,
> 
> Testing out 4.3-rc2, first thing I notice is that the VGA output is
> not working.  Specifically, the display is continuously powering on
> and off -- at no point is any image visible on the screen (I am expecting
> to see the console output).  The display connected to the HDMI output is
> working fine.
> 
> Linux 4.2 did not suffer from this problem.
> 
> In dmesg I see the following messages, which I do not see on a working
> kernel.  Full dmesg from 4.3-rc2 is attached (gzipped).
> 
>   [    0.115339] [drm:drm_calc_timestamping_constants] *ERROR* crtc
> 21: Can't calculate constants, dotclock = 0!
>   [    0.117582] [drm:intel_opregion_init] *ERROR* No ACPI video bus found
> 
> This is an older machine with Intel G45 graphics.
> 
> Unfortunately bisection is proving difficult, because the commits it
> wants me to test have a different problem: neither display comes up at
> all (both remain in standby).  Partial results follow.
> 
> Thanks,
>   Nick
> 
>   git bisect start 'drivers/gpu/drm/i915'
>   # bad: [1f93e4a96c9109378204c147b3eec0d0e8100fde] Linux 4.3-rc2
>   git bisect bad 1f93e4a96c9109378204c147b3eec0d0e8100fde
>   # good: [64291f7db5bd8150a74ad2036f1037e6a0428df2] Linux 4.2
>   git bisect good 64291f7db5bd8150a74ad2036f1037e6a0428df2
>   # skip: [a7a6c498927ea42c9a3b26e0caa5c854a980d58c] drm/i915:
> POSTING_READ() in intel_set_memory_cxsr()
>   git bisect skip a7a6c498927ea42c9a3b26e0caa5c854a980d58c
>   # skip: [031b698a77a70a6c394568034437b5486a44e868] drm/i915:
> Unconditionally do fb tracking invalidate in set_domain
>   git bisect skip 031b698a77a70a6c394568034437b5486a44e868
>   # skip: [adeca76d8e2b34b5c739a36f4191aed63080da40] drm/i915:
> Simplify i915_gem_execbuffer_retire_commands() parameters
>   git bisect skip adeca76d8e2b34b5c739a36f4191aed63080da40
>   # good: [369712e89404089fa559235bb1ee8fc40d976e6b] drm/i915: reduce
> duplicate conditions in i9xx_hpd_irq_handler
>   git bisect good 369712e89404089fa559235bb1ee8fc40d976e6b
>   # skip: [6eb1a6817246f1a67de4d6959a84d09efead5329] drm/i915: Read wm
> values from hardware at init on CHV
>   git bisect skip 6eb1a6817246f1a67de4d6959a84d09efead5329
>   # bad: [d14e7b6d1d8747826cb900db852351c550e00fdd] drm/i915: Check DP
> link status on long hpd too
>   git bisect bad d14e7b6d1d8747826cb900db852351c550e00fdd
>   # skip: [fe36f55d4d4447679923fc74564786ae423ca4bd] drm/i915/gtt:
> Cleanup page directory encoding
>   git bisect skip fe36f55d4d4447679923fc74564786ae423ca4bd


> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Ville Syrjälä]

On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
> Hi,
> 
> This issue is still present in 4.3-rc4.
> 
> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
> > not working.  Specifically, the display is continuously powering on
> > and off -- at no point is any image visible on the screen (I am expecting
> > to see the console output).  The display connected to the HDMI output is
> > working fine.
> >
> > Linux 4.2 did not suffer from this problem.
> >
> > In dmesg I see the following messages, which I do not see on a working
> > kernel.  Full dmesg from 4.3-rc2 is attached (gzipped).
> >
> >   [    0.115339] [drm:drm_calc_timestamping_constants] *ERROR* crtc
> > 21: Can't calculate constants, dotclock = 0!
> >   [    0.117582] [drm:intel_opregion_init] *ERROR* No ACPI video bus found
> >
> > This is an older machine with Intel G45 graphics.
> 
> I was able to identify the commit which fixed my boot crashes, so I
> cherry-picked 80aa93128653 ("drm/i915: disable_shared_pll doesn't
> work on pre-gen5") on top of all otherwise untestable commits.  This
> allowed bisection to proceed:
> 
>   b8afb9113c519a8bd742f7df8c424b0af69a75cd is the first bad commit
>   commit b8afb9113c519a8bd742f7df8c424b0af69a75cd
>   Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
>   Date:   Mon Jun 29 15:25:48 2015 +0300
> 
>       drm/i915: Keep GMCH DPLL VGA mode always disabled
> 
>       We disable the DPLL VGA mode when enabling the DPLL, but we enaable it
>       again when disabling the DPLL. Having VGA mode enabled even in unused
>       DPLLs can cause problems for CHV, so it seems wiser to always keep it
>       disabled. And let's just do that on all GMCH platforms to keep things
>       as similar as possible between them.
> 
>       Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>       Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
>       Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
>   :040000 040000 7797d596e73ecf75723375028decd25fbe332ee0
> 9f90a92eec483919853d68563bbb09a71a305532 M	drivers
> 
> Unfortunately it does not revert cleanly on master.

@@ -1790,13 +1790,13 @@ static void i9xx_disable_pll(struct intel_crtc *crtc)
        /* Make sure the pipe isn't still relying on us */
        assert_pipe_disabled(dev_priv, pipe);
 
-       I915_WRITE(DPLL(pipe), 0);
+       I915_WRITE(DPLL(pipe), DPLL_VGA_MODE_DIS);
        POSTING_READ(DPLL(pipe));
 }


That hunk is the only relevant part for your machine. Can you try to revert
just that manually?

But I'm really surprised that would have any effect since we only used
to enable "VGA mode" when the DPLL is off. And when the DPLL is off,
there's nothing on the screen anyway.

-- 
Ville Syrjälä
Intel OTC
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Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Nick Bowler]

On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
>> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
>> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
>> > not working.  Specifically, the display is continuously powering on
>> > and off -- at no point is any image visible on the screen (I am
>> > expecting to see the console output).  The display connected to the
>> > HDMI output is working fine.
[...]
>>   b8afb9113c519a8bd742f7df8c424b0af69a75cd is the first bad commit
>>   commit b8afb9113c519a8bd742f7df8c424b0af69a75cd
>>   Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>   Date:   Mon Jun 29 15:25:48 2015 +0300
>>
>>       drm/i915: Keep GMCH DPLL VGA mode always disabled
[...]
> @@ -1790,13 +1790,13 @@ static void i9xx_disable_pll(struct intel_crtc
> *crtc)
>         /* Make sure the pipe isn't still relying on us */
>         assert_pipe_disabled(dev_priv, pipe);
>
> -       I915_WRITE(DPLL(pipe), 0);
> +       I915_WRITE(DPLL(pipe), DPLL_VGA_MODE_DIS);
>         POSTING_READ(DPLL(pipe));
>  }
>
>
> That hunk is the only relevant part for your machine. Can you try to revert
> just that manually?
>
> But I'm really surprised that would have any effect since we only used
> to enable "VGA mode" when the DPLL is off. And when the DPLL is off,
> there's nothing on the screen anyway.

Nevertheless, manually reverting just that hunk seems to fix it.

Thanks,
  Nick

Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Ville Syrjälä]

[-- Attachment #1: Type: text/plain, Size: 2018 bytes --]

On Wed, Oct 07, 2015 at 10:29:22AM -0400, Nick Bowler wrote:
> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> > On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
> >> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
> >> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
> >> > not working.  Specifically, the display is continuously powering on
> >> > and off -- at no point is any image visible on the screen (I am
> >> > expecting to see the console output).  The display connected to the
> >> > HDMI output is working fine.
> [...]
> >>   b8afb9113c519a8bd742f7df8c424b0af69a75cd is the first bad commit
> >>   commit b8afb9113c519a8bd742f7df8c424b0af69a75cd
> >>   Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>   Date:   Mon Jun 29 15:25:48 2015 +0300
> >>
> >>       drm/i915: Keep GMCH DPLL VGA mode always disabled
> [...]
> > @@ -1790,13 +1790,13 @@ static void i9xx_disable_pll(struct intel_crtc
> > *crtc)
> >         /* Make sure the pipe isn't still relying on us */
> >         assert_pipe_disabled(dev_priv, pipe);
> >
> > -       I915_WRITE(DPLL(pipe), 0);
> > +       I915_WRITE(DPLL(pipe), DPLL_VGA_MODE_DIS);
> >         POSTING_READ(DPLL(pipe));
> >  }
> >
> >
> > That hunk is the only relevant part for your machine. Can you try to revert
> > just that manually?
> >
> > But I'm really surprised that would have any effect since we only used
> > to enable "VGA mode" when the DPLL is off. And when the DPLL is off,
> > there's nothing on the screen anyway.
> 
> Nevertheless, manually reverting just that hunk seems to fix it.

Hmm. You said VGA has the problem, but HDMI does not. Was the problem
happening even when you have both displays enabled at the same time, or
just when VGA was enabled alone?

I've attached two potential patches that might help. Can you give a try
to just patch 1, and if that alone doesn't help then both patches
together?

-- 
Ville Syrjälä
Intel OTC

[-- Attachment #2: 0001-restore-DPLL-write.patch --]
[-- Type: text/x-diff, Size: 768 bytes --]

>From 98cbf947740861f0e1bf625dfaedbd43be7746ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 7 Oct 2015 18:23:26 +0300
Subject: [PATCH 1/2] restore DPLL write

---
 drivers/gpu/drm/i915/intel_display.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 147e700..f4fdff9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1743,6 +1743,8 @@ static void i9xx_enable_pll(struct intel_crtc *crtc)
 			   I915_READ(DPLL(!crtc->pipe)) | DPLL_DVO_2X_MODE);
 	}
 
+	I915_WRITE(reg, dpll);
+
 	/* Wait for the clocks to stabilize. */
 	POSTING_READ(reg);
 	udelay(150);
-- 
2.4.9


[-- Attachment #3: 0002-enable-VGA-mode-before-P1-P2-write.patch --]
[-- Type: text/x-diff, Size: 893 bytes --]

>From 78ee4cbf2560891e59e6ae58fbcd197a34012819 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 7 Oct 2015 18:27:33 +0300
Subject: [PATCH 2/2] enable VGA mode before P1/P2 write

---
 drivers/gpu/drm/i915/intel_display.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f4fdff9..036550f 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1743,6 +1743,12 @@ static void i9xx_enable_pll(struct intel_crtc *crtc)
 			   I915_READ(DPLL(!crtc->pipe)) | DPLL_DVO_2X_MODE);
 	}
 
+	/*
+	 * Apparently we need to have VGA mode enabled
+	 * prior to writing P1/P2, otherwise they won't take.
+	 */
+	I915_WRITE(reg, 0);
+
 	I915_WRITE(reg, dpll);
 
 	/* Wait for the clocks to stabilize. */
-- 
2.4.9


[-- Attachment #4: Type: text/plain, Size: 159 bytes --]

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Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Nick Bowler]

On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Wed, Oct 07, 2015 at 10:29:22AM -0400, Nick Bowler wrote:
>> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>> > On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
>> >> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
>> >> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
>> >> > not working.  Specifically, the display is continuously powering on
>> >> > and off -- at no point is any image visible on the screen (I am
>> >> > expecting to see the console output).  The display connected to the
>> >> > HDMI output is working fine.
>> [...]
> Hmm. You said VGA has the problem, but HDMI does not. Was the problem
> happening even when you have both displays enabled at the same time, or
> just when VGA was enabled alone?

When I boot with HDMI cable disconnected, there is no change in behaviour
for the VGA output.

> I've attached two potential patches that might help. Can you give a try
> to just patch 1, and if that alone doesn't help then both patches
> together?

I will try.

Cheers,
  Nick

Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Nick Bowler]

On 10/7/15, Nick Bowler <nbowler@draconx.ca> wrote:
> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>> On Wed, Oct 07, 2015 at 10:29:22AM -0400, Nick Bowler wrote:
>>> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>>> > On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
>>> >> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
>>> >> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
>>> >> > not working.  Specifically, the display is continuously powering on
>>> >> > and off -- at no point is any image visible on the screen (I am
>>> >> > expecting to see the console output).  The display connected to the
>>> >> > HDMI output is working fine.
>>> [...]
>> Hmm. You said VGA has the problem, but HDMI does not. Was the problem
>> happening even when you have both displays enabled at the same time, or
>> just when VGA was enabled alone?
>
> When I boot with HDMI cable disconnected, there is no change in behaviour
> for the VGA output.

Clarification: normally both displays are connected.  So the original issue is
that only one of two displays are working.

Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Nick Bowler]

On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Wed, Oct 07, 2015 at 10:29:22AM -0400, Nick Bowler wrote:
>> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>> > On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
>> >> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
>> >> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
>> >> > not working.  Specifically, the display is continuously powering on
>> >> > and off -- at no point is any image visible on the screen (I am
>> >> > expecting to see the console output).  The display connected to the
>> >> > HDMI output is working fine.
>> [...]
> I've attached two potential patches that might help. Can you give a try
> to just patch 1, and if that alone doesn't help then both patches
> together?

Patch #1: no change.
Patch #1+#2: this works.

Regards,
  Nick

Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

[Ville Syrjälä]

On Wed, Oct 07, 2015 at 02:50:34PM -0400, Nick Bowler wrote:
> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> > On Wed, Oct 07, 2015 at 10:29:22AM -0400, Nick Bowler wrote:
> >> On 10/7/15, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> >> > On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
> >> >> On 9/24/15, Nick Bowler <nbowler@draconx.ca> wrote:
> >> >> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
> >> >> > not working.  Specifically, the display is continuously powering on
> >> >> > and off -- at no point is any image visible on the screen (I am
> >> >> > expecting to see the console output).  The display connected to the
> >> >> > HDMI output is working fine.
> >> [...]
> > I've attached two potential patches that might help. Can you give a try
> > to just patch 1, and if that alone doesn't help then both patches
> > together?
> 
> Patch #1: no change.
> Patch #1+#2: this works.

Cool. I can see similar effects when manually frobbing the register on
my 946GZ, except somehow it still manages to work without these
patches. Not quite sure why that is.

But anyway, I'll polish the patches a bit and send them out.

-- 
Ville Syrjälä
Intel OTC
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