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List:       devicetree
Subject:    Re: [PATCH 3/4] arm: boot: dts: am335x-evm: Make charge delay a DT parameter for tsc
From:       Hartmut Knaack <knaack.h () gmx ! de>
Date:       2014-10-31 21:09:34
Message-ID: 5453FA8E.3080204 () gmx ! de
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Vignesh R schrieb am 27.10.2014 12:08:
> 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.
> 
I would recommend to use a few colons to separate some thoughts. Also, limit to 80 \
chars per line would be beneficial. See inline.
> 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
<...> speed, hence needs to be <...>
> +			 avoiding false pen-up event. Start from a lower value say 0x400
<...> pen-up events. Start from a lower value, like 0x400, and increase <...>
> +			 and increase value until false pen-up events are avoided. The
> +			 pen-up detection happens immediately after the charge step
<...> charge step, so this <...>
> +			 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 {
> 

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