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

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Date:	Wed, 12 Aug 2015 13:44:22 -0500
From:	Michael Welling <mwelling@...e.org>
To:	Vignesh R <vigneshr@...com>
Cc:	Michael Welling <mwelling@...e.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	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

On Wed, Aug 12, 2015 at 11:56:36AM +0530, Vignesh R wrote:
> 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.

Do you see any reason why you would want a different delay for each step of
the conversion on the same touchscreen?

The user would need to know the number of steps what each of the steps do.

> 
> >  - 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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