Hello Lothar,

On Tue, Jul 05, 2016 at 02:08:38PM +0200, Lothar Waßmann wrote:

On Tue, 5 Jul 2016 12:09:02 +0200 Uwe Kleine-König wrote:

quoted

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?

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

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |