Patch "drm/i915: Fix IPS related flicker" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915: Fix IPS related flicker

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-fix-ips-related-flicker.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rodrigo Vivi <[email protected]>
Date: Thu, 28 May 2015 11:07:11 -0700
Subject: drm/i915: Fix IPS related flicker
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From: Rodrigo Vivi <[email protected]>

commit ac88cd738425e04dbed3706621cf613a00708834 upstream.

We cannot let IPS enabled with no plane on the pipe:

BSpec: "IPS cannot be enabled until after at least one plane has been enabled for at least one vertical blank." and "IPS must be disabled while there is still at least one plane enabled on the same pipe as IPS." This restriction apply to HSW and BDW.

However a shortcut path on update primary plane function to make primary plane invisible by setting DSPCTRL to 0 was leting IPS enabled while there was no
other plane enabled on the pipe causing flickerings that we were believing that it was caused by that other restriction where ips cannot be used when pixel rate is greater than 95% of cdclok.

v2: Don't mess with Atomic path as pointed out by Ville.

Reference: https://bugs.freedesktop.org/show_bug.cgi?id=85583

---
 drivers/gpu/drm/i915/intel_display.c |   13 +++++++++++++
 drivers/gpu/drm/i915/intel_drv.h     |    1 +
 2 files changed, 14 insertions(+)

@@ -12499,6 +12499,16 @@ intel_check_primary_plane(struct drm_pla
 				intel_crtc->atomic.wait_vblank = true;
 		}
 
+		/*
+		 * FIXME: Actually if we will still have any other plane enabled
+		 * on the pipe we could let IPS enabled still, but for
+		 * now lets consider that when we make primary invisible
+		 * by setting DSPCNTR to 0 on update_primary_plane function
+		 * IPS needs to be disable.
+		 */
+		if (!state->visible || !fb)
+			intel_crtc->atomic.disable_ips = true;
+
 		intel_crtc->atomic.fb_bits |=
 			INTEL_FRONTBUFFER_PRIMARY(intel_crtc->pipe);
 

@@ -12590,6 +12600,9 @@ static void intel_begin_crtc_commit(stru
 	if (intel_crtc->atomic.disable_fbc)
 		intel_fbc_disable(dev);
 
+	if (intel_crtc->atomic.disable_ips)
+		hsw_disable_ips(intel_crtc);
+
 	if (intel_crtc->atomic.pre_disable_primary)
 		intel_pre_disable_primary(crtc);
 

@@ -424,6 +424,7 @@ struct intel_crtc_atomic_commit {
 	/* Sleepable operations to perform before commit */
 	bool wait_for_flips;
 	bool disable_fbc;
+	bool disable_ips;
 	bool pre_disable_primary;
 	bool update_wm;
 	unsigned disabled_planes;

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/drm-i915-fix-ips-related-flicker.patch