From: Alexandru Stan <amstan@chromium.org>
To: "Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Lee Jones" <lee.jones@linaro.org>,
"Daniel Thompson" <daniel.thompson@linaro.org>,
"Jingoo Han" <jingoohan1@gmail.com>,
"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
"Heiko Stuebner" <heiko@sntech.de>,
"Rob Herring" <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org, linux-fbdev@vger.kernel.org,
Alexandru Stan <amstan@chromium.org>,
linux-pwm@vger.kernel.org,
Douglas Anderson <dianders@chromium.org>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
linux-rockchip@lists.infradead.org,
Matthias Kaehlcke <mka@chromium.org>,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/3] PWM backlight interpolation adjustments
Date: Mon, 20 Jul 2020 21:25:19 -0700 [thread overview]
Message-ID: <20200721042522.2403410-1-amstan@chromium.org> (raw)
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
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next reply other threads:[~2020-07-21 8:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 4:25 Alexandru Stan [this message]
2020-07-21 4:25 ` [PATCH 1/3] backlight: pwm_bl: Fix interpolation Alexandru Stan
2020-09-04 11:27 ` Daniel Thompson
2020-07-21 4:25 ` [PATCH 2/3] backlight: pwm_bl: Artificially add 0% during interpolation Alexandru Stan
2020-08-07 8:21 ` daniel
2020-08-13 13:45 ` Daniel Thompson
2020-09-04 11:38 ` Daniel Thompson
2020-09-07 7:50 ` Daniel Vetter
2020-09-09 14:45 ` Daniel Thompson
2020-09-09 15:03 ` Daniel Vetter
2020-09-10 7:47 ` Daniel Vetter
2020-09-09 18:42 ` Alexandru M Stan
2020-08-05 21:04 ` [PATCH 0/3] PWM backlight interpolation adjustments Alexandru M Stan
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