linux/drivers/video
Peter Ujfalusi ec665b756e backlight: gpio-backlight: Correct initial power state handling
The default-on property - or the def_value via legacy pdata) should be
handled as:
if it is 1, the backlight must be enabled (kept enabled)
if it is 0, the backlight must be disabled (kept disabled)

This only works for the case when default-on is set. If it is not set then
the brightness of the backlight is set to 0. Now if the backlight is
enabled by external driver (graphics) the backlight will stay disabled since
the brightness is configured as 0. The backlight will not turn on.

In order to minimize screen flickering during device boot:

The initial brightness should be set to 1.

If booted in non DT mode or no phandle link to the backlight node:
follow the def_value/default-on to select UNBLANK or POWERDOWN

If in DT boot we have phandle link then leave the GPIO in a state which the
bootloader left it and let the user of the backlight to configure it
further.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
2019-09-02 15:54:52 +01:00
..
backlight backlight: gpio-backlight: Correct initial power state handling 2019-09-02 15:54:52 +01:00
console dummycon: Sprinkle locking checks 2019-06-12 20:26:55 +02:00
fbdev dma-mapping updates for Linux 5.3 2019-07-12 15:13:55 -07:00
logo treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
display_timing.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
hdmi.c video/hdmi: Dropped static functions from kernel doc 2019-06-04 14:04:04 +02:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
of_display_timing.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
of_videomode.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
vgastate.c Video: vgastate: fixed a spacing coding style 2018-10-08 12:57:35 +02:00
videomode.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00