Re: [PATCH] drm/i915/gen9: Give one extra block per line for SKL plane WM calculations

From: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
To: "chris@chris-wilson.co.uk" <chris@chris-wilson.co.uk>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH] drm/i915/gen9: Give one extra block per line for SKL plane WM calculations
Date: Mon, 8 Aug 2016 19:00:46 +0000	[thread overview]
Message-ID: <1470682843.2424.29.camel@intel.com> (raw)
In-Reply-To: <20160808183514.GA9246@nuc-i3427.alporthouse.com>

Em Seg, 2016-08-08 às 19:35 +0100, Chris Wilson escreveu:
> On Mon, Aug 08, 2016 at 06:25:49PM +0000, Zanoni, Paulo R wrote:
> > 
> > Em Qui, 2016-08-04 às 16:51 -0700, Matt Roper escreveu:
> > > 
> > > On Thu, Aug 04, 2016 at 07:36:15PM -0400, Lyude wrote:
> > > > 
> > > > 
> > > > Reviewed-by: Lyude <cpaul@redhat.com>
> > > 
> > > Merged to dinq.  Thanks for the quick review.
> > 
> > Regression? This patch makes my SKL machine fail any modesets. I
> > now
> > boot to a blinking screen where X keeps trying to start and fails.
> 
> -intel has been fixing up failed multi-CRTC modesets since seemingly
> forever on skl, that fail due to WM being exceeded. And why would
> modesetting even be trying to use a non-tiled framebuffer?

I'm just using my distro's default driver, and Debian uses modesetting
now.

I did switch to xf86-video-intel and I found something interesting: the
machine boots correctly, but then if I stop+restart lightdm, I get a
black screen. The difference here is that X doesn't abort, it tries to
keep working despite the black screen:

[    46.483] (EE) intel(0): failed to set mode: Invalid argument [22]
[    46.485] (II) intel(0): EDID vendor "SDC", prod id 16970
[    46.485] (II) intel(0): Printing DDC gathered Modelines:
[    46.485] (II) intel(0): Modeline "3200x1800"x0.0  361.31  3200 3248
3280 3316  1800 1802 1807 1816 -hsync -vsync (109.0 kHz eP)
[    46.485] (II) intel(0): Modeline "3200x1800"x0.0  361.31  3200 3248
3280 3680  1800 1802 1807 2045 -hsync -vsync (98.2 kHz e)
[    46.794] (--) intel(0): HDMI max TMDS frequency 225000KHz
[    46.969] (EE) intel(0): failed to set mode: Invalid argument [22]

And dmesg has the same message as when using xf86-video-modesetting:

[   46.928018] [drm:skl_compute_plane_wm] Requested display
configuration exceeds system watermark limitations
[   46.928021] [drm:skl_compute_plane_wm] Plane 1.0: blocks required =
4/0, lines required = 1/31

Notice that this is the distro's driver version:
2:2.99.917+git20160706-1

So it looks like switching back to xf86-video-intel won't be a perfect
fix.

Anyway, while using the DDX to work around Kernel bugs may have some
benefits, it's probably best to try to push for an appropriate Kernel
fix, especially now that xf86-video-modesetting is gaining some market
share...

> -Chris
> 
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