From: Daniel Vetter <daniel@ffwll.ch>
To: Philipp Zabel <p.zabel@pengutronix.de>
Cc: kernel@pengutronix.de, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm_modes: calculate nominal vrefresh in drm_display_mode_from_videomode
Date: Fri, 4 Dec 2015 08:57:40 +0100 [thread overview]
Message-ID: <20151204075740.GT10243@phenom.ffwll.local> (raw)
In-Reply-To: <1449140964.3339.20.camel@pengutronix.de>
On Thu, Dec 03, 2015 at 12:09:24PM +0100, Philipp Zabel wrote:
> Am Donnerstag, den 03.12.2015, 11:22 +0100 schrieb Thierry Reding:
> > On Thu, Dec 03, 2015 at 10:50:07AM +0100, Daniel Vetter wrote:
> > > On Thu, Dec 03, 2015 at 09:55:44AM +0100, Philipp Zabel wrote:
> > > > Use drm_mode_vrefresh to update the vrefresh field after changing the
> > > > modes' timings and flags.
> > > >
> > > > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> > > > ---
> > > > drivers/gpu/drm/drm_modes.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> > > > index cd74a09..b624be8 100644
> > > > --- a/drivers/gpu/drm/drm_modes.c
> > > > +++ b/drivers/gpu/drm/drm_modes.c
> > > > @@ -611,6 +611,8 @@ void drm_display_mode_from_videomode(const struct videomode *vm,
> > > > dmode->flags |= DRM_MODE_FLAG_DBLSCAN;
> > > > if (vm->flags & DISPLAY_FLAGS_DOUBLECLK)
> > > > dmode->flags |= DRM_MODE_FLAG_DBLCLK;
> > > > + dmode->vrefresh = 0;
> > >
> > > Rendundant. Or I'm blind.
> >
> > Unfortunately it isn't. drm_mode_vrefresh() is somewhat odd in that
> > it'll return the existing mode->vrefresh if it is > 0. I'm thinking that
> > perhaps it'd be useful to factor out the computation code into a
> > separate function, say drm_mode_calc_vrefresh(), and use that where you
> > really want to compute the value and at the same time use it to simplify
> > drm_mode_vrefresh() as well.
>
> I don't understand the intention behind the drm_mode_vrefresh (and
> drm_mode_hsync) functions, but replacing all instances of
>
> mode->vrefresh = drm_mode_vrefresh(mode)
>
> with something that always calculates the vrefresh sounds like a good
> idea to me.
Premature micro-optimization to avoid recomputing hrefresh/vrefresh all
the time I think. I'd drop this, and then redo your patch on top to also
drop the = 0 assignment.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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prev parent reply other threads:[~2015-12-04 7:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-03 8:55 [PATCH] drm_modes: calculate nominal vrefresh in drm_display_mode_from_videomode Philipp Zabel
2015-12-03 9:50 ` Daniel Vetter
2015-12-03 10:22 ` Thierry Reding
2015-12-03 11:09 ` Philipp Zabel
2015-12-04 7:57 ` Daniel Vetter [this message]
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