[PATCH 3/4] arm: boot: dts: am335x-evm: Make charge delay a DT parameter for tsc
From: vigneshr@ti.com (Vignesh R)
Date: 2014-10-27 11:10:35
Also in:
linux-devicetree, linux-iio, linux-input, linux-omap, lkml
Subsystem:
input (keyboard, mouse, joystick, touchscreen) drivers, open firmware and flattened device tree bindings, the rest · Maintainers:
Dmitry Torokhov, Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds
The charge delay value is by default 0xB000. But it can be set to lower values on some boards as long as false pen-ups are avoided. Lowering the value increases the sampling rate (though current sampling rate is sufficient for tsc operation). Hence charge delay has been made a DT parameter. Signed-off-by: Vignesh R <vigneshr@ti.com> --- .../devicetree/bindings/input/touchscreen/ti-tsc-adc.txt | 13 +++++++++++++ arch/arm/boot/dts/am335x-evm.dts | 1 + 2 files changed, 14 insertions(+)
diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
index 878549ba814d..ac62769e70e4 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt@@ -28,6 +28,18 @@ Required properties: ti,adc-channels: List of analog inputs available for ADC. AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7. +Optional properties: +- child "tsc" + ti,charge-delay: Length of touch screen charge delay step in terms of + ADC clock cycles. Charge delay value should be large in order + to avoid false pen-up events. This value affects the overall + sampling speed hence need to be kept as low as possible while + avoiding false pen-up event. Start from a lower value say 0x400 + and increase value until false pen-up events are avoided. The + pen-up detection happens immediately after the charge step + so this does in fact function as a hardware knob for adjusting + the amount of "settling time". + Example: tscadc: tscadc at 44e0d000 { compatible = "ti,am3359-tscadc";
@@ -36,6 +48,7 @@ Example: ti,x-plate-resistance = <200>; ti,coordiante-readouts = <5>; ti,wire-config = <0x00 0x11 0x22 0x33>; + ti,charge-delay = <0xB000>; }; adc {
diff --git a/arch/arm/boot/dts/am335x-evm.dts b/arch/arm/boot/dts/am335x-evm.dts
index e2156a583de7..80be0462298b 100644
--- a/arch/arm/boot/dts/am335x-evm.dts
+++ b/arch/arm/boot/dts/am335x-evm.dts@@ -641,6 +641,7 @@ ti,x-plate-resistance = <200>; ti,coordinate-readouts = <5>; ti,wire-config = <0x00 0x11 0x22 0x33>; + ti,charge-delay = <0xB000>; }; adc {
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1.9.1