Re: [PATCH] input: ti_am335x_tsc: Add open delay parameter

[Michael Welling <mwelling@ieee.org>]

On Thu, Aug 20, 2015 at 05:41:30PM +0530, Vignesh R wrote:
> 
> 
> On 08/19/2015 11:38 PM, Michael Welling wrote:
> > On Wed, Aug 12, 2015 at 01:44:22PM -0500, Michael Welling wrote:
> >> 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@ieee.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?
> 
> 
> Sorry for the delay,
> 
> I haven't seen different delays being used for different channels on
> 4-wire TSC ( not sure of 5-wire or 8 wire designs). Since this is DT
> change, I just wanted to make sure more flexibility is provided.
> 
> >>
> >> The user would need to know the number of steps what each of the steps do.
> >>
> 
> 
> What I was thinking was making open-delay configurable per channel (one
> entry for X+, X-, Y+, Y-).
> 
> For example, for a 4-wire TSC:
> ti,chan-open-delay = <0x30 0x100 0x20 0x10>; /* for X+, X-, Y+, Y- */
>

What about the readings for the pressure?
 
> 
> >>>
> >>>>  - 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
> 
> -- 
> Regards
> Vignesh