Re: [PATCH 0/3] Experimental freesync video mode optimization

From: Daniel Vetter <daniel@ffwll.ch>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: stylon.wang@amd.com, thong.thai@amd.com, shashank.sharma@amd.com,
	dri-devel@lists.freedesktop.org, nicholas.kazlauskas@amd.com,
	Aurabindo Pillai <aurabindo.pillai@amd.com>,
	amd-gfx@lists.freedesktop.org, wayne.lin@amd.com,
	alexander.deucher@amd.com, christian.koenig@amd.com
Subject: Re: [PATCH 0/3] Experimental freesync video mode optimization
Date: Fri, 22 Jan 2021 10:44:19 +0100	[thread overview]
Message-ID: <YAqec2/YTOTicjZC@phenom.ffwll.local> (raw)
In-Reply-To: <YAqeHZlDBrgALLo9@phenom.ffwll.local>

On Fri, Jan 22, 2021 at 10:42:53AM +0100, Daniel Vetter wrote:
> On Fri, Jan 22, 2021 at 10:32:48AM +0200, Pekka Paalanen wrote:
> > On Tue, 19 Jan 2021 10:50:26 -0500
> > Aurabindo Pillai <aurabindo.pillai@amd.com> wrote:
> > 
> > > Changes in V5
> > > =============
> > > 
> > > * More info in commit messages on the rationale of changes being added
> > > to the kernel.
> > > * Minor fixes
> > 
> > Hi,
> > 
> > thank you for adding the explanations in the commit messages I asked
> > for. It is now up to DRM maintainers to determine if this is
> > conceptually fine.
> > 
> > I do see that apparently setting the opt-in option does not yet taint
> > the kernel although Daniel Vetter suggested it might be a good idea. I
> > guess tainting the kernel would make it easier to remove this feature
> > in the future because it would be easier to dismiss people that claim a
> > kernel regression due to the removal.
> 
> Reading the descriptions I'm honestly not sure why this isn't enabled by
> default?
> 
> Maybe the explanations should also capture why this is maybe not a good
> idea ...

And also, if this is a bad idea uapi-vise, then it definitely needs to be
behind the tainting module option until we've sorted it out (and then just
enable it by default once that's done).
-Daniel

> -Daniel
> 
> > 
> > 
> > Thanks,
> > pq
> > 
> > 
> > > --
> > > 
> > > This patchset enables freesync video mode usecase where the userspace
> > > can request a freesync compatible video mode such that switching to this
> > > mode does not trigger blanking.
> > > 
> > > This feature is guarded by a module parameter which is disabled by
> > > default. Enabling this paramters adds additional modes to the driver
> > > modelist, and also enables the optimization to skip modeset when using
> > > one of these modes.
> > > 
> > > --
> > > 
> > > Aurabindo Pillai (3):
> > >   drm/amd/display: Add module parameter for freesync video mode
> > >   drm/amd/display: Add freesync video modes based on preferred modes
> > >   drm/amd/display: Skip modeset for front porch change
> > > 
> > >  drivers/gpu/drm/amd/amdgpu/amdgpu.h           |   1 +
> > >  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c       |  12 +
> > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 401 ++++++++++++++++--
> > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |   3 +
> > >  4 files changed, 382 insertions(+), 35 deletions(-)
> > > 
> > 
> 
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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