[v4,4/6] ARM: dts: AM335x: Make charge delay a DT parameter for TSC
diff mbox

Message ID 1415941651-28962-5-git-send-email-vigneshr@ti.com
State New, archived
Headers show

Commit Message

Vignesh Raghavendra Nov. 14, 2014, 5:07 a.m. UTC
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@ti.com>
---

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(+)

Comments

Tony Lindgren Nov. 14, 2014, 6:03 p.m. UTC | #1
* Vignesh R <vigneshr@ti.com> [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@ti.com>

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@atomide.com>

> ---
> 
> 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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Patch
diff mbox

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 {