From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: [PATCH 4/6] drm: Fix treatment of drm_vblank_offdelay in drm_vblank_on() Date: Tue, 9 Feb 2016 13:10:15 +0200 Message-ID: <20160209111015.GJ23290@intel.com> References: <1454894009-15466-1-git-send-email-mario.kleiner.de@gmail.com> <1454894009-15466-5-git-send-email-mario.kleiner.de@gmail.com> <20160209100618.GO11240@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20160209100618.GO11240@phenom.ffwll.local> Sender: stable-owner@vger.kernel.org To: Daniel Vetter Cc: Mario Kleiner , dri-devel@lists.freedesktop.org, linux@bernd-steinhauser.de, stable@vger.kernel.org, michel@daenzer.net, vbabka@suse.cz, daniel.vetter@ffwll.ch, alexander.deucher@amd.com, christian.koenig@amd.com List-Id: dri-devel@lists.freedesktop.org On Tue, Feb 09, 2016 at 11:06:18AM +0100, Daniel Vetter wrote: > On Mon, Feb 08, 2016 at 02:13:27AM +0100, Mario Kleiner wrote: > > drm_vblank_offdelay can have three different types of values: > >=20 > > < 0 is to be always treated the same as dev->vblank_disable_immedia= te > > =3D 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. > >=20 > > 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. > >=20 > > Signed-off-by: Mario Kleiner > > Cc: # 3.18+ > > 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 > > --- > > drivers/gpu/drm/drm_irq.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > >=20 > > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c > > index 5c27ad3..fb17c45 100644 > > --- a/drivers/gpu/drm/drm_irq.c > > +++ b/drivers/gpu/drm/drm_irq.c > > @@ -1492,8 +1492,8 @@ void drm_vblank_on(struct drm_device *dev, un= signed int pipe) > > * 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) !=3D 0 || > > - (!dev->vblank_disable_immediate && drm_vblank_offdelay =3D=3D= 0)) > > + if (atomic_read(&vblank->refcount) !=3D 0 || drm_vblank_offdelay = =3D=3D 0 || > > + (!dev->vblank_disable_immediate && drm_vblank_offdelay > 0)) >=20 > Hm, shouldn't we change this to only enable the vblank irq if we need= it, > i.e. offdelay =3D=3D 0? For delayed disabling there's kinda no need t= o enable > it superflously after a modeset, if userspace didn't yet ask for vbla= nk > timestamps. But then is was specifically added by Ville in cd19e52aee= 922, > so I guess someone really wants this. IIRC what I wanted was to just re-enable the interrupt for the offdelay= =3D=3D0 case. I think it just ended up as a mess due to changing some of the semantics of offdelay<0 vs. offdelay=3D=3D0 vs. disable_immediate durin= g the=20 review of the series. So yeah, given how drm_vblank_put() works now, I'= d just make this check for offdelay=3D=3D0. >=20 > Reviewed-by: Daniel Vetter >=20 > > WARN_ON(drm_vblank_enable(dev, pipe)); > > spin_unlock_irqrestore(&dev->vbl_lock, irqflags); > > } > > --=20 > > 1.9.1 > >=20 >=20 > --=20 > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch --=20 Ville Syrj=E4l=E4 Intel OTC