From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>,
Gustavo Padovan <gustavo@padovan.org>,
dri-devel@lists.freedesktop.org, marcheu@google.com,
Daniel Stone <daniels@collabora.com>,
seanpaul@google.com, Daniel Vetter <daniel.vetter@ffwll.ch>,
linux-kernel@vger.kernel.org, laurent.pinchart@ideasonboard.com,
Gustavo Padovan <gustavo.padovan@collabora.co.uk>,
John Harrison <John.C.Harrison@Intel.com>,
m.chehab@samsung.com
Subject: Re: [PATCH v7 0/3] drm: add explict fencing
Date: Tue, 8 Nov 2016 12:32:56 +0100 [thread overview]
Message-ID: <20161108113256.q52243qihb6kwe2h@phenom.ffwll.local> (raw)
In-Reply-To: <20161108103508.GH18604@nuc-i3427.alporthouse.com>
On Tue, Nov 08, 2016 at 10:35:08AM +0000, Chris Wilson wrote:
> On Tue, Nov 08, 2016 at 03:54:47PM +0900, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> >
> > Hi,
> >
> > This is yet another version of the DRM fences patches. Please refer
> > to the cover letter[1] in a previous version to check for more details.
>
> Explicit fencing is not a superset of the implicit fences. The driver
> may be using implicit fences (on a reservation object) to serialise
> asynchronous operations wrt to each other (such as dispatching threads
> to flush cpu caches to memory, manipulating page tables and the like
> before the flip). Since the user doesn't know about these operations,
> they are not included in the explicit fence they provide, at which point
> we can't trust their fence to the exclusion of the implicit fences...
My thoughts are that in atomic_check drivers just fill in the fence from
the reservation_object (i.e. the uapi implicit fencing part). If there's
any additional work that's queued up in ->prepare_fb then I guess the
driver needs to track that internally, but _only_ for kernel-internally
queued work.
The reason for that is that with explicit fencing we want to allow
userspace to overwrite any existing implicit fences that might hang
around.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2016-11-08 11:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-08 6:54 [PATCH v7 0/3] drm: add explict fencing Gustavo Padovan
2016-11-08 6:54 ` [PATCH v7 1/3] drm/fence: add in-fences support Gustavo Padovan
2016-11-08 11:06 ` Daniel Vetter
2016-11-08 15:27 ` Brian Starkey
2016-11-08 16:11 ` Daniel Vetter
2016-11-08 6:54 ` [PATCH v7 2/3] drm/fence: add fence timeline to drm_crtc Gustavo Padovan
2016-11-08 6:54 ` [PATCH v7 3/3] drm/fence: add out-fences support Gustavo Padovan
2016-11-08 13:15 ` Daniel Vetter
2016-11-09 2:39 ` Gustavo Padovan
2016-11-09 10:18 ` Daniel Vetter
2016-11-08 15:36 ` Brian Starkey
2016-11-08 10:35 ` [PATCH v7 0/3] drm: add explict fencing Chris Wilson
2016-11-08 11:32 ` Daniel Vetter [this message]
2016-11-08 11:45 ` Chris Wilson
2016-11-08 12:43 ` Daniel Vetter
2016-11-08 12:52 ` Chris Wilson
2016-11-08 12:44 ` Christian König
2016-11-08 12:52 ` Daniel Vetter
2016-11-08 13:18 ` Daniel Vetter
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