* Vignesh R <vigneshr@xxxxxx> [141113 21:42]:
> The charge delay value is by default 0x400. 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). In some boards, the value has to be
> increased to avoid false pen-up events. Hence, charge delay has been
> made a DT parameter.
>
> Signed-off-by: Vignesh R <vigneshr@xxxxxx>
As long as the input and DT people are OK with this, ack for
merging the .dts changes along with the input patches:
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
> ---
>
> v4:
> - Set charge delay to 0x400 as default. Most devices function normally
> at this value
>
> .../devicetree/bindings/input/touchscreen/ti-tsc-adc.txt | 15 +++++++++++++++
> arch/arm/boot/dts/am335x-evm.dts | 1 +
> 2 files changed, 16 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..6df5028a4ad3 100644
> --- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> +++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> @@ -28,6 +28,20 @@ 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 +50,7 @@ Example:
> ti,x-plate-resistance = <200>;
> ti,coordiante-readouts = <5>;
> ti,wire-config = <0x00 0x11 0x22 0x33>;
> + ti,charge-delay = <0x400>;
> };
>
> adc {
> diff --git a/arch/arm/boot/dts/am335x-evm.dts b/arch/arm/boot/dts/am335x-evm.dts
> index e2156a583de7..ce12f6ef1e28 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 = <0x400>;
> };
>
> adc {
> --
> 1.9.1
>
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