Re: [PATCH v3] backlight: gpio-backlight: Correct initial power state handling

On Wed, 31 Jul 2019, Peter Ujfalusi wrote:

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 <redacted>
---
Hi,

sorry for the delay, but got distracted a bit with the resend of this...
Let's try again ;)

Changes since v2 (https://lore.kernel.org/patchwork/patch/1002359/):
- Rebased on drm-next

Changes since v1:
- Implement similiar initial power state handling as pwm backlight have

Regards,
Peter

 drivers/video/backlight/gpio_backlight.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
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