From mboxrd@z Thu Jan 1 00:00:00 1970 From: thierry.reding@gmail.com (Thierry Reding) Date: Tue, 10 Nov 2015 18:32:57 +0100 Subject: [PATCH v4] pwm-backlight: Avoid backlight flicker when probed from DT In-Reply-To: <3447562.c3gSANEMio@phil> References: <1446483356-14338-1-git-send-email-p.zabel@pengutronix.de> <3447562.c3gSANEMio@phil> Message-ID: <20151110173257.GA21727@ulmo> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Nov 10, 2015 at 03:18:10PM +0100, Heiko Stuebner wrote: > Hi Philipp, > > Am Montag, 2. November 2015, 17:55:56 schrieb Philipp Zabel: > > If the driver is probed from the device tree, and there is a phandle > > 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. > > > > Signed-off-by: Philipp Zabel > > Reviewed-by: Christian Gmeiner > > this patch improves the white screen when booting a veyron chromebook > a lot. I still see a small white flash, but that can probably come from > the WIP edp driver. Some panels require a couple of frames before they actually enable. You 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. >>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 sending frames and finally "enables" the panel. With something like the simple panel driver you can influence this by setting the delay.enable field in the panel descriptor. See struct panel_desc in drivers/gpu/drm/panel/panel-simple.c Thierry -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: not available URL: