linux-kernel - Re: [PATCH] input: ti_am335x_tsc: Add open delay parameter

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Message-ID: <55CAE71C.4060505@ti.com>
Date:	Wed, 12 Aug 2015 11:56:36 +0530
From:	Vignesh R <vigneshr@...com>
To:	Michael Welling <mwelling@...e.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-input@...r.kernel.org>, Jonathan Cameron <jic23@...nel.org>,
	Brad Griffis <bgriffis@...com>
Subject: Re: [PATCH] input: ti_am335x_tsc: Add open delay parameter

Hi Michael,

+ Dmitry

On 08/12/2015 12:15 AM, Michael Welling wrote:
> Adds a device tree parameter to set the open delay on the touchscreen
> conversion steps. Increasing this parameter helps the touch accuracy on
> some screens.
> 
> Signed-off-by: Michael Welling <mwelling@...e.org>
> ---
>  .../bindings/input/touchscreen/ti-tsc-adc.txt          |  5 +++++
>  drivers/input/touchscreen/ti_am335x_tsc.c              | 18 ++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> index b1163bf..cb11fda 100644
> --- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> +++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> @@ -41,6 +41,11 @@ Optional properties:
>  			 charge step, so this does in fact function as a
>  			 hardware knob for adjusting the amount of "settling
>  			 time".
> +	ti,open-delay: Open delay applied to all touchscreen conversion steps.
> +			The value corresponds to the number of ADC clock
> +			cycles to wait after applying the step configuration
> +			registers and before sending the start of ADC
> +			conversion. Maximum value is 0x3FFFF.
>  

Since open-delay is per step, is it not better to allow specifying
open-delay per step like ti,chan-step-opendelay of adc? This will help
control open-delay for all the four wires.

>  - child "adc"
>  	ti,chan-step-opendelay: List of open delays for each channel of
> diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
> index 191a1b8..37a9729 100644
> --- a/drivers/input/touchscreen/ti_am335x_tsc.c
> +++ b/drivers/input/touchscreen/ti_am335x_tsc.c
> @@ -54,6 +54,7 @@ struct titsc {
>  	u32			inp_xp, inp_xn, inp_yp, inp_yn;
>  	u32			step_mask;
>  	u32			charge_delay;
> +	u32			open_delay;
>  };
>  
>  static unsigned int titsc_readl(struct titsc *ts, unsigned int reg)
> @@ -148,7 +149,7 @@ static void titsc_step_config(struct titsc *ts_dev)
>  	end_step = first_step + tsc_steps;
>  	for (i = end_step - ts_dev->coordinate_readouts; i < end_step; i++) {
>  		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
> -		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
> +		titsc_writel(ts_dev, REG_STEPDELAY(i), ts_dev->open_delay);
>  	}
>  
>  	config = 0;
> @@ -172,7 +173,7 @@ static void titsc_step_config(struct titsc *ts_dev)
>  	end_step = first_step + ts_dev->coordinate_readouts;
>  	for (i = first_step; i < end_step; i++) {
>  		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
> -		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
> +		titsc_writel(ts_dev, REG_STEPDELAY(i), ts_dev->open_delay);
>  	}
>  
>  	/* Make CHARGECONFIG same as IDLECONFIG */
> @@ -188,13 +189,13 @@ static void titsc_step_config(struct titsc *ts_dev)
>  			STEPCONFIG_INP(ts_dev->inp_xp);
>  	titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
>  	titsc_writel(ts_dev, REG_STEPDELAY(end_step),
> -			STEPCONFIG_OPENDLY);
> +			ts_dev->open_delay);
>  
>  	end_step++;
>  	config |= STEPCONFIG_INP(ts_dev->inp_yn);
>  	titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
>  	titsc_writel(ts_dev, REG_STEPDELAY(end_step),
> -			STEPCONFIG_OPENDLY);
> +			ts_dev->open_delay);
>  
>  	/* The steps end ... end - readouts * 2 + 2 and bit 0 for TS_Charge */
>  	stepenable = 1;
> @@ -392,6 +393,15 @@ static int titsc_parse_dt(struct platform_device *pdev,
>  		dev_warn(&pdev->dev, "ti,charge-delay not specified\n");
>  	}
>  
> +	err = of_property_read_u32(node, "ti,open-delay",
> +				   &ts_dev->open_delay);
> +	/*
> +	 * If ti,open-delay value is not specified, then use
> +	 * STEPCONFIG_OPENDLY as the default value.
> +	 */
> +	if (err < 0)
> +		ts_dev->open_delay = STEPCONFIG_OPENDLY;
> +
>  	return of_property_read_u32_array(node, "ti,wire-config",
>  			ts_dev->config_inp, ARRAY_SIZE(ts_dev->config_inp));
>  }
> 

-- 
Regards
Vignesh
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