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 <[email protected]> --- .../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@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 { -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
