From mboxrd@z Thu Jan  1 00:00:00 1970
From: Heiko =?ISO-8859-1?Q?St=FCbner?= <heiko@sntech.de>
Date: Fri, 27 Nov 2015 10:18:04 +0000
Subject: Re: [PATCH v4] pwm-backlight: Avoid backlight flicker when probed from DT
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References: <1446483356-14338-1-git-send-email-p.zabel@pengutronix.de>
 <3447562.c3gSANEMio@phil> <20151110173257.GA21727@ulmo>
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Hi Thierry,

Am Dienstag, 10. November 2015, 18:32:57 schrieb Thierry Reding:
> On Tue, Nov 10, 2015 at 03:18:10PM +0100, Heiko Stuebner wrote:
> > Hi Philipp,
> >=20
> > Am Montag, 2. November 2015, 17:55:56 schrieb Philipp Zabel:
> > > If the driver is probed from the device tree, and there is a phan=
dle
> > > property set on it, and the enable GPIO is already configured as =
output,
> > > and the backlight is currently disabled, keep it disabled.
> > > If all these conditions are met, assume there will be some other =
driver
> > > that can enable the backlight at the appropriate time.
> > >=20
> > > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> > > Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
> >=20
> > this patch improves the white screen when booting a veyron chromebo=
ok
> > a lot. I still see a small white flash, but that can probably come =
from
> > the WIP edp driver.
>=20
> Some panels require a couple of frames before they actually enable. Y=
ou
> may want to look at the datasheet of your panel to see if it has some=

> specific requirement and update the panel driver with that.
>=20
> From a high-level view the way that this is supposed to work is that
> your encoder driver (e.g. eDP) "prepares" the panel, then starts send=
ing
> frames and finally "enables" the panel. With something like the simpl=
e
> panel driver you can influence this by setting the delay.enable field=
 in
> the panel descriptor.
>=20
> See struct panel_desc in drivers/gpu/drm/panel/panel-simple.c

Thanks for the pointers :-)

Just to follow up a little bit, after moving to Yakir's Analogix-dp dri=
ver=20
from=20the chromeos-one I was using till now, that actually works nicely =
for me=20
and even the short flash is gone.


Heiko
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