[Intel-gfx] [PATCH] drm/i915: Fix ilk watermarks calculation when primary plane is disabled

[Ander Conselvan de Oliveira]

On Fedora 21 or 22, when the transition from the X server to the wayland
compositor is done, the CRTC with the login screen is left active with a
disabled fb. A cursor ioctl after the transition causes the watermarks
to be updated, but due to the logic in intel_crtc_active() checking for
the primary plane fb, the update considers all planes to be disabled,
untimately setting the wrong watermark values and causing screen
flicker. Since the crtc is active, a modeset done later is skipped and
replaced with a flip, which doesn't update the watermarks.

This regression was introduced somewhere between v3.16 and v3.17.
Another issue prevented me from doing a full bisect, but the issue was
introduced in one of the following skipped commits:

    commit 7707e6535f43328e05e4729ac96eee864b90e8a4
    Author: Rob Clark <robdclark at gmail.com>
    Date:   Thu Jul 17 23:30:04 2014 -0400

        drm/i915: use helpers

    commit ca5a1b9ba0fb5291b555a23b76dbe5f6c30bfd7a
    Merge: c7dbc6c 3488229
    Author: Dave Airlie <airlied at redhat.com>
    Date:   Wed Jul 9 10:38:42 2014 +1000

        Merge tag 'drm-intel-next-2014-06-20' of git://anongit.freedesktop.org/drm-intel into drm-next

    commit c51f71679042a5f388d9580ffbede14c897f1e86
    Merge: b957f45 7b3c29f
    Author: Dave Airlie <airlied at redhat.com>
    Date:   Sat Jul 19 16:43:41 2014 +1000

        Merge tag 'drm-intel-next-2014-07-11' of git://anongit.freedesktop.org/drm-intel into drm-next

This patch is a simplified version of the following commits:

    commit 3dd512fbda0d87d1c3fb44bf878b262baee98fb6
    Author: Matt Roper <matthew.d.roper at intel.com>
    Date:   Fri Feb 27 10:12:00 2015 -0800

        drm/i915: Kill intel_crtc->cursor_{width, height} (v2)

    commit 54da691deb123c045259ebf4f5c67381244f58f1
    Author: Thomas Gummerer <t.gummerer at gmail.com>
    Date:   Thu May 14 09:16:39 2015 +0200

        drm/i915: fix screen flickering

    commit 3ef00284e6a48f7deb0784ccca0478ebb7d4bcfc
    Author: Matt Roper <matthew.d.roper at intel.com>
    Date:   Mon Mar 9 10:19:24 2015 -0700

        drm/i915: Use crtc->state->active in ilk/skl watermark calculations (v3)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90508
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1218688
Cc: stable at vger.kernel.org
Cc: Dave Airlie <airlied at gmail.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 24d77dd..3d67f8e 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1898,16 +1898,24 @@ static void ilk_compute_wm_parameters(struct drm_crtc *crtc,
 	enum pipe pipe = intel_crtc->pipe;
 	struct drm_plane *plane;
 
-	if (!intel_crtc_active(crtc))
+	if (!intel_crtc->active)
 		return;
 
 	p->active = true;
 	p->pipe_htotal = intel_crtc->config->base.adjusted_mode.crtc_htotal;
 	p->pixel_rate = ilk_pipe_pixel_rate(dev, crtc);
-	p->pri.bytes_per_pixel = crtc->primary->fb->bits_per_pixel / 8;
+
+
+	if (crtc->primary->fb)
+		p->pri.bytes_per_pixel = crtc->primary->fb->bits_per_pixel / 8;
+	else
+		p->pri.bytes_per_pixel = 4;
+
 	p->cur.bytes_per_pixel = 4;
+
 	p->pri.horiz_pixels = intel_crtc->config->pipe_src_w;
-	p->cur.horiz_pixels = intel_crtc->cursor_width;
+	p->cur.horiz_pixels = intel_crtc->base.cursor->state->crtc_w;
+
 	/* TODO: for now, assume primary and cursor planes are always enabled. */
 	p->pri.enabled = true;
 	p->cur.enabled = true;
-- 
2.1.0