Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Jani Nikula]

On Sun, 28 Aug 2016, Andrea Arcangeli <aarcange@redhat.com> wrote:
> Skylake was already singled out, but it doesn't cover the XPS 13 L332X
> model which is based on IvyBridge.
>
> The commit that introduced the regression is
> 1d6da87a3241deb13d073c4125d19ed0e5a0c62c

That's a merge commit, the real one is

commit a05628195a0d9f3173dd9aa76f482aef692e46ee
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Mon Apr 11 10:23:51 2016 +0300

    drm/i915: Get panel_type from OpRegion panel details

> The Skylake workaround for the regression was introduced in commit
> aeddda06c1a704bb97c8a7bfe7a472120193bd56
>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
>  drivers/gpu/drm/i915/intel_opregion.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
> index adca262..ca17ab6 100644
> --- a/drivers/gpu/drm/i915/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/intel_opregion.c
> @@ -1073,12 +1073,14 @@ intel_opregion_get_panel_type(struct drm_i915_private *dev_priv)
>  	}
>  
>  	/*
> -	 * FIXME On Dell XPS 13 9350 the OpRegion panel type (0) gives us
> -	 * low vswing for eDP, whereas the VBT panel type (2) gives us normal
> -	 * vswing instead. Low vswing results in some display flickers, so
> -	 * let's simply ignore the OpRegion panel type on SKL for now.
> +	 * FIXME On Dell XPS 13 9350 and Dell XPS 13 L322X the
> +	 * OpRegion panel type (0) gives us low vswing for eDP,
> +	 * whereas the VBT panel type (2) gives us normal vswing
> +	 * instead. Low vswing results in some display flickers, so
> +	 * let's simply ignore the OpRegion panel type on SKL and
> +	 * IVYBRIDGE for now.
>  	 */

If it's an Iybridge, there's no low vswing, and that explanation is
false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
on an unpatched kernel.

Doesn't mean there can't be something else wrong with the mode you get
using a different panel_type. And this makes me wonder what the point is
in trying to patch up the commit instead of reverting.


BR,
Jani.



> -	if (IS_SKYLAKE(dev_priv)) {
> +	if (IS_SKYLAKE(dev_priv) || IS_IVYBRIDGE(dev_priv)) {
>  		DRM_DEBUG_KMS("Ignoring OpRegion panel type (%d)\n", ret - 1);
>  		return -ENODEV;
>  	}
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Andrea Arcangeli]

On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
> If it's an Iybridge, there's no low vswing, and that explanation is
> false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
> on an unpatched kernel.

What I should look for when trying those two settings? Will they
successfully fix my problem with intel_backlight with upstream 4.8-rc?

I thought it had to be the same issue as on skylake as I get the
backlight flikering at low frequency but getting brighter and darker
in a cycle lasting a few seconds and I thought there couldn't be too
many other random bugs that ends up with the same side effect.

It looks like the hardware actually broke, software issue isn't the
first thing that comes to mind. As it's hard to imagine a timer in the
kernel reprogramming the backlight setting higher and lower just to
annoy me :). First in fact I thought at a plasma issue, but I tried to
downgrade the kernel first as that was quicker than downgrading
kde/plasma... I initially thought there were two userland daemons
stepping into each other toes.

Another thing is that if I keep decreasing the brightness the screen
eventually goes off and it returns on as I increase the backlight
level again (then low freq flickering starts). With acpi_video0 even
at the lowest brightness setting of 0, it never turns off the screen
completely.

> Doesn't mean there can't be something else wrong with the mode you get
> using a different panel_type. And this makes me wonder what the point is
> in trying to patch up the commit instead of reverting.

Reverting the whole thing would be sure fine with me, I don't know
what the benefits there should be in using intel_backlight instead of
acpi_video0 like the previous code did, but I couldn't imagine too
many hw to behave like this if intel_backlight clearly has to work
stable for someone or it wouldn't exist in the first place.

This is just a "echo " into a backlight file if I tweak the backlight
settings... doesn't sound performance critical stuff to me, ACPI will
do just fine. However I'm not even sure how this problem could surface
in the first place without the kernel continuously reprogramming the
hw values.
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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Jani Nikula]

On Mon, 29 Aug 2016, Andrea Arcangeli <aarcange@redhat.com> wrote:
> On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
>> If it's an Iybridge, there's no low vswing, and that explanation is
>> false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
>> on an unpatched kernel.
>
> What I should look for when trying those two settings? Will they
> successfully fix my problem with intel_backlight with upstream 4.8-rc?
>
> I thought it had to be the same issue as on skylake as I get the
> backlight flikering at low frequency but getting brighter and darker
> in a cycle lasting a few seconds and I thought there couldn't be too
> many other random bugs that ends up with the same side effect.

Your Ivybridge does not have low voltage swing *and* low voltage swing
has nothing to do with the backlight. The regressing commit may be the
same for you, but the failure mode appears to be completely different.

BR,
Jani.




-- 
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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Andrea Arcangeli]

On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
> If it's an Iybridge, there's no low vswing, and that explanation is
> false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
> on an unpatched kernel.

CC'ed Martin who filed the bz, he can reproduce too
https://bugzilla.kernel.org/show_bug.cgi?id=151731

Since you can reproduce would you have the time to test the two above
options on stock 4.7.x/4.8-rc and help tracking this down? I'm afraid
I won't be able to test it today and I'll be mostly offline for a week
starting tomorrow.

Thanks,
Andrea
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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Martin van Es]

Hi Andrea,

I'd be happy to test, but what am I testing when applying these boot 
parameters? In other words: what should I report?

And just to be sure, I THINK I own an IVB but intel is not very vocal about it 
when searching for familyname. I have a

vendor_id       : GenuineIntel
cpu family      : 6
model           : 58
model name      : Intel(R) Core(TM) i7-3537U CPU @ 2.00GHz
stepping        : 9
microcode       : 0x17

Regards,
Martin

On maandag 29 augustus 2016 20:48:43 CEST Andrea Arcangeli wrote:
> On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
> > If it's an Iybridge, there's no low vswing, and that explanation is
> > false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
> > on an unpatched kernel.
> 
> CC'ed Martin who filed the bz, he can reproduce too
> https://bugzilla.kernel.org/show_bug.cgi?id=151731
> 
> Since you can reproduce would you have the time to test the two above
> options on stock 4.7.x/4.8-rc and help tracking this down? I'm afraid
> I won't be able to test it today and I'll be mostly offline for a week
> starting tomorrow.
> 
> Thanks,
> Andrea
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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Jani Nikula]

On Tue, 30 Aug 2016, Martin van Es <martin@mrvanes.com> wrote:
> Hi Andrea,
>
> I'd be happy to test, but what am I testing when applying these boot 
> parameters? In other words: what should I report?

The point is, for an ivybridge setting those parameters should not make
*any* difference.

BR,
Jani.


>
> And just to be sure, I THINK I own an IVB but intel is not very vocal about it 
> when searching for familyname. I have a
>
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 58
> model name      : Intel(R) Core(TM) i7-3537U CPU @ 2.00GHz
> stepping        : 9
> microcode       : 0x17
>
> Regards,
> Martin
>
> On maandag 29 augustus 2016 20:48:43 CEST Andrea Arcangeli wrote:
>> On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
>> > If it's an Iybridge, there's no low vswing, and that explanation is
>> > false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
>> > on an unpatched kernel.
>> 
>> CC'ed Martin who filed the bz, he can reproduce too
>> https://bugzilla.kernel.org/show_bug.cgi?id=151731
>> 
>> Since you can reproduce would you have the time to test the two above
>> options on stock 4.7.x/4.8-rc and help tracking this down? I'm afraid
>> I won't be able to test it today and I'll be mostly offline for a week
>> starting tomorrow.
>> 
>> Thanks,
>> Andrea

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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Martin van Es]

On dinsdag 30 augustus 2016 11:13:40 CEST Jani Nikula wrote:
> On Tue, 30 Aug 2016, Martin van Es <martin@mrvanes.com> wrote:
> > Hi Andrea,
> > 
> > I'd be happy to test, but what am I testing when applying these boot
> > parameters? In other words: what should I report?
> 
> The point is, for an ivybridge setting those parameters should not make
> *any* difference.

I can confirm that neither i915.edp_vswing=1 nor i915.edp_vswing=2 fixes the 
problem in 4.7.2 for me (intel_backlight devices takes precedence).

Best regards,
Martin

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Re: [PATCH 1/1] drm: i915: don't use OpRegion for XPS 13 IvyBridge

[Jani Nikula]

On Mon, 29 Aug 2016, Andrea Arcangeli <aarcange@redhat.com> wrote:
> On Mon, Aug 29, 2016 at 10:24:38AM +0300, Jani Nikula wrote:
>> If it's an Iybridge, there's no low vswing, and that explanation is
>> false. You can verify by trying i915.edp_vswing=1 or i915.edp_vswing=2
>> on an unpatched kernel.
>
> CC'ed Martin who filed the bz, he can reproduce too
> https://bugzilla.kernel.org/show_bug.cgi?id=151731
>
> Since you can reproduce would you have the time to test the two above
> options on stock 4.7.x/4.8-rc and help tracking this down? I'm afraid
> I won't be able to test it today and I'll be mostly offline for a week
> starting tomorrow.

As I tried to explain, the low voltage swing is not related to backlight
issues.

BR,
Jani.

>
> Thanks,
> Andrea

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