6.6-stable review patch. If anyone has any objections, please let me know.
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From: Dragan Simic dsimic@manjaro.org
commit 8c51521de18755d4112a77a598a348b38d0af370 upstream.
Increase the frequency of the PWM signal that drives the LED backlight of the Pinebook Pro's panel, from about 1.35 KHz (which equals to the PWM period of 740,740 ns), to exactly 8 kHz (which equals to the PWM period of 125,000 ns). Using a higher PWM frequency for the panel backlight, which reduces the flicker, can only be beneficial to the end users' eyes.
On top of that, increasing the backlight PWM signal frequency reportedly eliminates the buzzing emitted from the Pinebook Pro's built-in speakers when certain backlight levels are set, which cause some weird interference with some of the components of the Pinebook Pro's audio chain.
The old value for the backlight PWM period, i.e. 740,740 ns, is pretty much an arbitrary value that was selected during the very early bring-up of the Pinebook Pro, only because that value seemed to minimize horizontal line distortion on the display, which resulted from the old X.org drivers causing screen tearing when dragging windows around. That's no longer an issue, so there are no reasons to stick with the old PWM period value.
The lower and the upper backlight PWM frequency limits for the Pinebook Pro's panel, according to its datasheet, are 200 Hz and 10 kHz, respectively. [1] These changes still leave some headroom, which may have some positive effects on the lifetime expectancy of the panel's backlight LEDs.
[1] https://files.pine64.org/doc/datasheet/PinebookPro/NV140FHM-N49_Rev.P0_20160...
Fixes: 5a65505a6988 ("arm64: dts: rockchip: Add initial support for Pinebook Pro") Cc: stable@vger.kernel.org Reported-by: Nikola Radojevic nikola@radojevic.rs Signed-off-by: Dragan Simic dsimic@manjaro.org Tested-by: Nikola Radojević nikola@radojevic.rs Link: https://lore.kernel.org/r/2a23b6cfd8c0513e5b233b4006ee3d3ed09b824f.172280565... Signed-off-by: Heiko Stuebner heiko@sntech.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/boot/dts/rockchip/rk3399-pinebook-pro.dts | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm64/boot/dts/rockchip/rk3399-pinebook-pro.dts +++ b/arch/arm64/boot/dts/rockchip/rk3399-pinebook-pro.dts @@ -32,7 +32,7 @@ backlight: edp-backlight { compatible = "pwm-backlight"; power-supply = <&vcc_12v>; - pwms = <&pwm0 0 740740 0>; + pwms = <&pwm0 0 125000 0>; };
bat: battery {