Re: [PATCH 2/2] backlight: pwm_bl: add configurable delay between re-enabling PWM and switching back

On Fri, 27 Oct 2017, Rob Herring wrote:

On Thu, Oct 26, 2017 at 02:49:46PM +0200, Lothar Waßmann wrote:

quoted

When switching the backlight on, the LCD may need some time to adjust
to the configured PWM duty cycle. Add a configurable delay between
configuring the PWM and enabling the backlight regulator to account
for this.

Signed-off-by: Lothar Waßmann <redacted>
---
 .../bindings/leds/backlight/pwm-backlight.txt      |  4 ++++
 drivers/video/backlight/pwm_bl.c                   | 22 +++++++++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
index 764db86..95594c3 100644
--- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

@@ -17,6 +17,10 @@ Optional properties:
                "pwms" property (see PWM binding[0])
   - enable-gpios: contains a single GPIO specifier for the GPIO which enables
                   and disables the backlight (see GPIO binding[1])
+  - turn-on-delay-ms: delay in milliseconds between configuring the PWM
+		  and switching PWM on. This may be required to eliminate
+		  flicker when switching the PWM on after it has been
+		  disabled.

The subject talks about turning on the backlight regulator, but this 
only talks about the PWM.

From my understanding "switching PWM on" = enabling the regulator.

I don't see any disparity here.  Or am I missing something?

quoted

 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
 [1]: Documentation/devicetree/bindings/gpio/gpio.txt

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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