This is a note to let you know that I have just added a patch titled

drm: Fix treatment of drm_vblank_offdelay in drm_vblank_on() (v2)

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at:

http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt5.

If you, or anyone else, feels it should not be added to this tree, please reply to this email.

For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks. -Kamal

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From 5e9a7dec7acb148f29a0b24f66c6e22caa1aa592 Mon Sep 17 00:00:00 2001

From: Mario Kleiner mario.kleiner.de@gmail.com Date: Fri, 12 Feb 2016 20:30:30 +0100 Subject: drm: Fix treatment of drm_vblank_offdelay in drm_vblank_on() (v2)

commit bb74fc1bf3072bd3ab4ed5f43afd287a63baf2d7 upstream.

drm_vblank_offdelay can have three different types of values:

< 0 is to be always treated the same as dev->vblank_disable_immediate = 0 is to be treated as "never disable vblanks"

0 is to be treated as disable immediate if kms driver wants it

that way via dev->vblank_disable_immediate. Otherwise it is a disable timeout in msecs.

This got broken in Linux 3.18+ for the implementation of drm_vblank_on. If the user specified a value of zero which should always reenable vblank irqs in this function, a kms driver could override the users choice by setting vblank_disable_immediate to true. This patch fixes the regression and keeps the user in control.

v2: Only reenable vblank if there are clients left or the user requested to "never disable vblanks" via offdelay 0. Enabling vblanks even in the "delayed disable" case (offdelay > 0) was specifically added by Ville in commit cd19e52aee922 ("drm: Kick start vblank interrupts at drm_vblank_on()"), but after discussion it turns out that this was done by accident.

Citing Ville: "I think it just ended up as a mess due to changing some of the semantics of offdelay<0 vs. offdelay==0 vs. disable_immediate during the review of the series. So yeah, given how drm_vblank_put() works now, I'd just make this check for offdelay==0."

Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

Cc: michel@daenzer.net Cc: vbabka@suse.cz Cc: ville.syrjala@linux.intel.com Cc: daniel.vetter@ffwll.ch Cc: dri-devel@lists.freedesktop.org Cc: alexander.deucher@amd.com Cc: christian.koenig@amd.com Signed-off-by: Dave Airlie airlied@redhat.com Signed-off-by: Kamal Mostafa kamal@canonical.com --- drivers/gpu/drm/drm_irq.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index b50fa0a..6447b48 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1338,8 +1338,7 @@ void drm_vblank_on(struct drm_device *dev, int crtc) * re-enable interrupts if there are users left, or the * user wishes vblank interrupts to be enabled all the time. */ - if (atomic_read(&vblank->refcount) != 0 || - (!dev->vblank_disable_immediate && drm_vblank_offdelay == 0)) + if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0) WARN_ON(drm_vblank_enable(dev, crtc)); spin_unlock_irqrestore(&dev->vbl_lock, irqflags); } -- 2.7.0