From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Date: Tue, 05 Jul 2016 12:22:28 +0000 Subject: Re: [PATCH 2/3] video: fbdev: imxfb: enable lcd regulator in .probe Message-Id: <20160705122228.GO16643@pengutronix.de> List-Id: References: <1457380425-20244-1-git-send-email-u.kleine-koenig@pengutronix.de> <1457380425-20244-3-git-send-email-u.kleine-koenig@pengutronix.de> <56E2AA80.4050908@ti.com> <20160420191727.GS29108@pengutronix.de> <20160705100902.GM16643@pengutronix.de> <20160705140838.52014e4b@ipc1.ka-ro> In-Reply-To: <20160705140838.52014e4b@ipc1.ka-ro> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: linux-arm-kernel@lists.infradead.org Hello Lothar, On Tue, Jul 05, 2016 at 02:08:38PM +0200, Lothar Wa=DFmann wrote: > On Tue, 5 Jul 2016 12:09:02 +0200 Uwe Kleine-K=F6nig wrote: > > To reach my goal to keep the display on (showing whatever the bootloader > > initialized the display with) until the application starts caring for > > the display some driver must enable the regulator. The only candidates > > are the lcd driver (i.e. the patch under discussion) or some mechanism > > in the fb core. As there doesn't seem to be code in the core (and the > > core is dead?) what do you suggest me to do? > >=20 > The simplefb driver (CONFIG_FB_SIMPLE) is designed for exactly this > purpose. If you rely on the bootloader's framebuffer being preserved > until your application starts without any driver that reserves the > corresponding memory, the framebuffer contents may be corrupted by the > booting kernel. I don't want to use the simplefb driver because the application makes use of planes which isn't supported by simplefb. To prevent the framebuffer being overwritten a chunk of memory at the end of RAM is reserved (similar to how simplefb is supposed to work). And even without my usecase of a persistent splash screen, if the fb is used as console, it should not be disabled either. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ |