Re: [PATCH 0/3] PWM backlight interpolation adjustments
From: Alexandru M Stan
Date: Wed Aug 05 2020 - 17:10:28 EST
On Mon, Jul 20, 2020 at 9:27 PM Alexandru Stan <amstan@xxxxxxxxxxxx> wrote:
> I was trying to adjust the brightness for a new chromebook:
> Like a lot of panels, the low end needs to be cropped,
> and now that we have the interpolation stuff I wanted to make use of it
> and bake in even the curve.
> I found the behavior a little unintuitive and non-linear. See patch 1
> for a suggested fix for this.
> Unfortunatelly a few veyron dts files were relying on this
> (perhaps weird) behavior. Those devices also want a minimum brightness.
> The issue is that they also want the 0% point for turning off the
> So the idea here is to change those dts files to only say <3 255> (patch
> 3), and add in a virtual 0% point at the bottom of the scale (patch 2).
> We have to do this conditionally because it seems some devices like to
> have the scale inverted:
> % git grep "brightness-levels\s*=\s*<\s*[1-9]"|cat
> arch/arm/boot/dts/tegra124-apalis-eval.dts: brightness-levels = <255 231 223 207 191 159 127 0>;
> Alexandru Stan (3):
> backlight: pwm_bl: Fix interpolation
> backlight: pwm_bl: Artificially add 0% during interpolation
> ARM: dts: rockchip: Remove 0 point in backlight
> arch/arm/boot/dts/rk3288-veyron-jaq.dts | 2 +-
> arch/arm/boot/dts/rk3288-veyron-minnie.dts | 2 +-
> arch/arm/boot/dts/rk3288-veyron-tiger.dts | 2 +-
> drivers/video/backlight/pwm_bl.c | 78 +++++++++++-----------
> 4 files changed, 42 insertions(+), 42 deletions(-)
Let me know if you would like me to make any changes to my patches.
Alexandru M Stan