From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandru M Stan Date: Wed, 05 Aug 2020 21:04:09 +0000 Subject: Re: [PATCH 0/3] PWM backlight interpolation adjustments Message-Id: List-Id: References: <20200721042522.2403410-1-amstan@chromium.org> In-Reply-To: <20200721042522.2403410-1-amstan@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Thierry Reding , =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz , Heiko Stuebner , Rob Herring Cc: devicetree@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-pwm@vger.kernel.org, Douglas Anderson , dri-devel@lists.freedesktop.org, linux-kernel , "open list:ARM/Rockchip SoC..." , Matthias Kaehlcke , Enric Balletbo i Serra , linux-arm-kernel@lists.infradead.org On Mon, Jul 20, 2020 at 9:27 PM Alexandru Stan wrote: > > I was trying to adjust the brightness for a new chromebook: > https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2291209 > 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 > display. > https://github.com/torvalds/linux/commit/6233269bce47bd450196a671ab28eb1ec5eb88d9#diff-e401ae20091bbfb311a062c464f4f47fL23 > > 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(-) > > -- > 2.27.0 > Hello, Friendly ping. Let me know if you would like me to make any changes to my patches. Thanks, Alexandru M Stan