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* [PATCH v3 0/3] PWM backlight interpolation adjustments
@ 2020-10-22  5:04 Alexandru Stan
  2020-10-22  5:04 ` [PATCH v3 3/3] backlight: pwm_bl: Fix interpolation Alexandru Stan
  2020-11-01 15:33 ` [PATCH v3 0/3] PWM backlight interpolation adjustments Heiko Stuebner
  0 siblings, 2 replies; 6+ messages in thread
From: Alexandru Stan @ 2020-10-22  5:04 UTC (permalink / raw)
  To: Heiko Stuebner, Rob Herring, Andy Gross, Bjorn Andersson,
	Thierry Reding, Uwe Kleine-König, Lee Jones,
	Daniel Thompson, Jingoo Han, Bartlomiej Zolnierkiewicz
  Cc: Douglas Anderson, Matthias Kaehlcke, Enric Balletbo i Serra,
	Alexandru Stan, devicetree, dri-devel, linux-arm-kernel,
	linux-arm-msm, linux-fbdev, linux-kernel, linux-pwm,
	linux-rockchip

I was trying to adjust the brightness-levels for the trogdor boards:
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2291209
Like on a lot of panels, trogdor's 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 that's customary to have on chromebooks.

I found the current behavior of the pwm_bl driver a little unintuitive
and non-linear. See patch 1 for a suggested fix for this.

A few veyron dts files were relying on this (perhaps weird) behavior.
Those devices also want a minimum brightness like trogdor, so changed
them to use the new way.

Finally, given that trogdor's dts is part of linux-next now, add the
brightness-levels to it, since that's the original reason I was looking at
this.

Changes in v3:
- Reordered patches, since both dts changes will work just fine
  even before the driver change.
- Rewrote a bit of the commit message to describe the new policy,
  as Daniel suggested.
- Removed redundant s64 for something that's always positive

Changes in v2:
- Fixed type promotion in the driver
- Removed "backlight: pwm_bl: Artificially add 0% during interpolation",
  userspace works just fine without it because it already knows how to use
  bl_power for turning off the display.
- Added brightness-levels to trogdor as well, now the dts is upstream.


Alexandru Stan (3):
  ARM: dts: rockchip: veyron: Remove 0 point from brightness-levels
  arm64: dts: qcom: trogdor: Add brightness-levels
  backlight: pwm_bl: Fix interpolation

 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 +-
 arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi |  9 +++
 drivers/video/backlight/pwm_bl.c             | 70 +++++++++-----------
 5 files changed, 43 insertions(+), 42 deletions(-)

-- 
2.28.0


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-11-04 15:54 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-22  5:04 [PATCH v3 0/3] PWM backlight interpolation adjustments Alexandru Stan
2020-10-22  5:04 ` [PATCH v3 3/3] backlight: pwm_bl: Fix interpolation Alexandru Stan
2020-10-28 15:12   ` Daniel Thompson
2020-11-02 18:52     ` Alexandru M Stan
2020-11-04 15:54   ` Lee Jones
2020-11-01 15:33 ` [PATCH v3 0/3] PWM backlight interpolation adjustments Heiko Stuebner

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