Patch "drm/vblank: Tune drm_crtc_accurate_vblank_count() WARN down to a debug" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

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

    drm/vblank: Tune drm_crtc_accurate_vblank_count() WARN down to a debug

to the 4.14-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-vblank-tune-drm_crtc_accurate_vblank_count-warn-down-to-a-debug.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From a111fbc4c44d2981f1a8fef64418685be5e30280 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Mon, 23 Oct 2017 18:25:40 +0300
Subject: drm/vblank: Tune drm_crtc_accurate_vblank_count() WARN down to a debug
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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From: Ville Syrjälä <ville.syrjala@linux.intel.com>

commit a111fbc4c44d2981f1a8fef64418685be5e30280 upstream.

Since commit 632c6e4edef1 ("drm/vblank: Fix flip event vblank count")
even drivers that don't implement accurate vblank timestamps will end
up using drm_crtc_accurate_vblank_count(). That leads to a WARN every
time drm_crtc_arm_vblank_event() gets called. The could be as often
as every frame for each active crtc.

Considering drm_crtc_accurate_vblank_count() is never any worse than
the drm_vblank_count() we used previously, let's just skip the WARN
unless DRM_UT_VBL is enabled. That way people won't be bothered by
this unless they're debugging vblank code. And let's also change it
to WARN_ONCE() so that even when you're debugging vblank code you
won't get drowned by constant WARNs.

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: "Szyprowski, Marek" <m.szyprowski@samsung.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Reported-by: Andrzej Hajda <a.hajda@samsung.com>
Fixes: 632c6e4edef1 ("drm/vblank: Fix flip event vblank count")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171023152540.15364-1-ville.syrjala@linux.intel.com
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/drm_vblank.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -311,8 +311,8 @@ u32 drm_crtc_accurate_vblank_count(struc
 	u32 vblank;
 	unsigned long flags;
 
-	WARN(!dev->driver->get_vblank_timestamp,
-	     "This function requires support for accurate vblank timestamps.");
+	WARN_ONCE(drm_debug & DRM_UT_VBL && !dev->driver->get_vblank_timestamp,
+		  "This function requires support for accurate vblank timestamps.");
 
 	spin_lock_irqsave(&dev->vblank_time_lock, flags);
 


Patches currently in stable-queue which might be from ville.syrjala@linux.intel.com are

queue-4.14/drm-edid-don-t-send-non-zero-yq-in-avi-infoframe-for-hdmi-1.x-sinks.patch
queue-4.14/drm-vblank-fix-flip-event-vblank-count.patch
queue-4.14/drm-vblank-tune-drm_crtc_accurate_vblank_count-warn-down-to-a-debug.patch