From: Ondrej Jirman megous@megous.com
[ Upstream commit 86be5c789690eb08656b08c072c50a7b02bf41f1 ]
Some outputs from the RTL8723CS are connected to the PL port (BT_WAKE_AP), which runs at 1.8V. When BT_WAKE_AP is high, the PL pin this signal is connected to is overdriven, and the whole PL port's voltage rises somewhat. This results in changing voltage on the R_PWM pin (PL10), which is the cause for backlight flickering very noticeably when typing on a Bluetooth keyboard, because backlight intensity is highly sensitive to the voltage of the R_PWM pin.
Limit the maximum WiFi/BT I/O voltage to 1.8V to avoid overdriving the PL port pins via BT and WiFi IO port signals. WiFi and BT functionality is unaffected by this change.
This completely stops the backlight flicker when using bluetooth.
Fixes: 91f480d40942 ("arm64: dts: allwinner: Add initial support for Pine64 PinePhone") Signed-off-by: Ondrej Jirman megous@megous.com Link: https://lore.kernel.org/r/20200703194842.111845-4-megous@megous.com Signed-off-by: Maxime Ripard maxime@cerno.tech Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone.dtsi | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone.dtsi index cefda145c3c9d..342733a20c337 100644 --- a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone.dtsi +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinephone.dtsi @@ -279,7 +279,7 @@ ®_dldo3 {
®_dldo4 { regulator-min-microvolt = <1800000>; - regulator-max-microvolt = <3300000>; + regulator-max-microvolt = <1800000>; regulator-name = "vcc-wifi-io"; };