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From: Mario Kleiner <mario.kleiner.de@gmail.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	linux@bernd-steinhauser.de, stable <stable@vger.kernel.org>,
	"Michel Dänzer" <michel@daenzer.net>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"alexander.deucher@amd.com" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH 5/6] drm: Prevent vblank counter jumps with timestamp based update method.
Date: Wed, 10 Feb 2016 19:36:40 +0100	[thread overview]
Message-ID: <56BB8338.7000504@gmail.com> (raw)
In-Reply-To: <CAKMK7uH2svOHdwHpS-_nm5Kbe0Ac_xMk6TCcorp2d35FQJiQ8Q@mail.gmail.com>

On 02/10/2016 06:17 PM, Daniel Vetter wrote:
> On Wed, Feb 10, 2016 at 5:28 PM, Mario Kleiner
> <mario.kleiner.de@gmail.com> wrote:
>> There's another scenario where this zero-ts case can be hit. If the driver
>> drm_vblank_init()'s - setting all timestamps to zero - and then code starts
>> using vblanks (drm_vblank_get()) without drm_vblank_on beforehand, which is
>> afaics the case with nouveau. Unless that's considered an error as well,
>> we'd need to init the timestamps to something non-zero but harmless like 1
>> usecs at drm_vblank_init() time?
>
> Both legacy modeset helpers and atomic ones assume by default that you
> start out with everything disabled. Pre-atomic drivers make that
> happen by calling disable_unused_functions() to shut down anything the
> bios has enabled. I think this can't happen.
>
> For drivers that do take over bootloader display config they must call
> vblank_on explicitly themselves, which i915 does.
>
>> What makes sense as output here? DRM_WARN_ONCE?
>
> I'd go with WARN_ON and tune it down if it's offensive. But WARN_ON
> patch for 4.6 of course.
> -Daniel
>

Ok, so does this one have your R-b for stable as is? What about a proper 
nouveau fix if i find one? Probably also for 4.6 then, given that this 
patch fixes it up good enough for stable?

-mario

  reply	other threads:[~2016-02-10 18:36 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-08  1:13 drm vblank regression fixes for Linux 4.4+ Mario Kleiner
2016-02-08  1:13 ` [PATCH 1/6] drm: No-Op redundant calls to drm_vblank_off() Mario Kleiner
2016-02-08  1:13   ` Mario Kleiner
2016-02-09  9:54   ` Daniel Vetter
2016-02-09  9:54     ` Daniel Vetter
2016-02-09 13:27     ` Mario Kleiner
2016-02-08  1:13 ` [PATCH 2/6] drm: Prevent vblank counter bumps > 1 with active vblank clients Mario Kleiner
2016-02-08  1:13   ` Mario Kleiner
2016-02-09  9:56   ` Daniel Vetter
2016-02-09  9:56     ` Daniel Vetter
2016-02-09 10:07     ` Ville Syrjälä
2016-02-09 10:07       ` Ville Syrjälä
2016-02-09 10:23       ` Daniel Vetter
2016-02-09 10:23         ` Daniel Vetter
2016-02-09 13:39         ` Mario Kleiner
2016-02-09 13:39           ` Mario Kleiner
2016-02-09 14:29           ` Daniel Vetter
2016-02-09 14:29             ` Daniel Vetter
2016-02-09 16:18             ` Mario Kleiner
2016-02-09 16:18               ` Mario Kleiner
2016-02-08  1:13 ` [PATCH 3/6] drm: Fix drm_vblank_pre/post_modeset regression from Linux 4.4 Mario Kleiner
2016-02-08  1:13   ` Mario Kleiner
2016-02-09 10:00   ` Daniel Vetter
2016-02-11 13:03   ` Vlastimil Babka
2016-02-08  1:13 ` [PATCH 4/6] drm: Fix treatment of drm_vblank_offdelay in drm_vblank_on() Mario Kleiner
2016-02-08  1:13   ` Mario Kleiner
2016-02-09 10:06   ` Daniel Vetter
2016-02-09 10:06     ` Daniel Vetter
2016-02-09 11:10     ` Ville Syrjälä
2016-02-09 11:10       ` Ville Syrjälä
2016-02-09 13:29       ` Mario Kleiner
2016-02-09 13:29         ` Mario Kleiner
2016-02-09 13:41         ` Ville Syrjälä
2016-02-09 13:41           ` Ville Syrjälä
2016-02-09 14:31           ` Daniel Vetter
2016-02-09 14:31             ` Daniel Vetter
2016-02-08  1:13 ` [PATCH 5/6] drm: Prevent vblank counter jumps with timestamp based update method Mario Kleiner
2016-02-08  1:13   ` Mario Kleiner
2016-02-09 10:09   ` Daniel Vetter
2016-02-09 13:53     ` Mario Kleiner
2016-02-09 14:11       ` Ville Syrjälä
2016-02-09 14:11         ` Ville Syrjälä
2016-02-09 15:03         ` Daniel Vetter
2016-02-09 15:03           ` Daniel Vetter
2016-02-10 16:28           ` Mario Kleiner
2016-02-10 16:28             ` Mario Kleiner
2016-02-10 17:17             ` Daniel Vetter
2016-02-10 18:36               ` Mario Kleiner [this message]
2016-02-10 19:34                 ` Daniel Vetter
2016-02-10 19:34                   ` Daniel Vetter
2016-02-08  1:13 ` [PATCH 6/6] drm/radeon/pm: Handle failure of drm_vblank_get Mario Kleiner
2016-02-09 10:10   ` Daniel Vetter

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