linux-kernel - [PATCH] ARM: dts: omap3-gta04: reduce panel backlight PWM frequency to 83Hz

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Message-Id: <954d43b570092fe92b8b49cf8f475c027d3d8342.1473066997.git.hns@goldelico.com>
Date:   Mon,  5 Sep 2016 11:16:38 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>, marek@...delico.com
Cc:     linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org,
        "H. Nikolaus Schaller" <hns@...delico.com>
Subject: [PATCH] ARM: dts: omap3-gta04: reduce panel backlight PWM frequency to 83Hz

This helps to get 100% intensity closer to "always on".

It compensates for an effect of dmtimer which at 100% still emits short
"off" impulses and the startup-time of the DC/DC converter makes
backlight intensity not reach full scale. The lower the PWM frequency
is, the smaller is this effect.

Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
---
 arch/arm/boot/dts/omap3-gta04.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
index c09a057..94f12dd 100644
--- a/arch/arm/boot/dts/omap3-gta04.dtsi
+++ b/arch/arm/boot/dts/omap3-gta04.dtsi
@@ -102,7 +102,7 @@
 
 	backlight {
 		compatible = "pwm-backlight";
-		pwms = <&pwm11 0 2000000 0>;
+		pwms = <&pwm11 0 12000000 0>;
 		pwm-names = "backlight";
 		brightness-levels = <0 11 20 30 40 50 60 70 80 90 100>;
 		default-brightness-level = <9>;	/* => 90 */
-- 
2.7.3