linux-kernel - Re: [PATCH] iio: adc: at91: Add support for Touchscreen Switches Closure Time

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Date:   Mon, 5 Sep 2016 21:12:07 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Nicolas Ferre <nicolas.ferre@...el.com>,
        Cristian Birsan <cristian.birsan@...rochip.com>,
        Ludovic Desroches <ludovic.desroches@...el.com>
Cc:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-iio@...r.kernel.org
Subject: Re: [PATCH] iio: adc: at91: Add support for Touchscreen Switches
 Closure Time

On 05/09/16 09:26, Nicolas Ferre wrote:
> Le 03/09/2016 à 18:24, Jonathan Cameron a écrit :
>> On 30/08/16 13:27, Nicolas Ferre wrote:
>>> On newer components compatible with the at91sam9x5, the Touchscreen
>>> Switches Closure Time or TSSCTIM value of the Touchscreen Mode Register is
>>> not filled at all.
>>> On some hardware, having no time indicated for it may lead to incoherent
>>> values and jitter.
>>> We fix this time to 10us as it is usually difficult to retrieve impedance
>>> values from LCD manufacturers.
>>>
>>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
>> Hi Nicolas,
>>
>> Stable / fixes material or just have it head for the next merge window?
> 
> Well, I would say that it's an addition of a feature that fixes a bad
> behavior ;-)
> So, in summary, I would just add it to next kernel revision.
> 
> Thanks for the heads-up. Bye,
Thanks

Applied to the togreg branch of iio.git - initially pushed out
as testing for the autobuilders to play with it.

Jonathan
> 
> 
>>> ---
>>>  drivers/iio/adc/at91_adc.c | 13 +++++++++++++
>>>  1 file changed, 13 insertions(+)
>>>
>>> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
>>> index 0438c68015e8..bbdac07f4aaa 100644
>>> --- a/drivers/iio/adc/at91_adc.c
>>> +++ b/drivers/iio/adc/at91_adc.c
>>> @@ -113,6 +113,7 @@
>>>  #define		AT91_ADC_TSMR_TSAV	(3 << 4)	/* Averages samples */
>>>  #define			AT91_ADC_TSMR_TSAV_(x)		((x) << 4)
>>>  #define		AT91_ADC_TSMR_SCTIM	(0x0f << 16)	/* Switch closure time */
>>> +#define			AT91_ADC_TSMR_SCTIM_(x)		((x) << 16)
>>>  #define		AT91_ADC_TSMR_PENDBC	(0x0f << 28)	/* Pen Debounce time */
>>>  #define			AT91_ADC_TSMR_PENDBC_(x)	((x) << 28)
>>>  #define		AT91_ADC_TSMR_NOTSDMA	(1 << 22)	/* No Touchscreen DMA */
>>> @@ -150,6 +151,7 @@
>>>  #define MAX_RLPOS_BITS         10
>>>  #define TOUCH_SAMPLE_PERIOD_US_RL      10000   /* 10ms, the SoC can't keep up with 2ms */
>>>  #define TOUCH_SHTIM                    0xa
>>> +#define TOUCH_SCTIM_US		10		/* 10us for the Touchscreen Switches Closure Time */
>>>  
>>>  /**
>>>   * struct at91_adc_reg_desc - Various informations relative to registers
>>> @@ -1001,7 +1003,9 @@ static void atmel_ts_close(struct input_dev *dev)
>>>  
>>>  static int at91_ts_hw_init(struct at91_adc_state *st, u32 adc_clk_khz)
>>>  {
>>> +	struct iio_dev *idev = iio_priv_to_dev(st);
>>>  	u32 reg = 0;
>>> +	u32 tssctim = 0;
>>>  	int i = 0;
>>>  
>>>  	/* a Pen Detect Debounce Time is necessary for the ADC Touch to avoid
>>> @@ -1034,11 +1038,20 @@ static int at91_ts_hw_init(struct at91_adc_state *st, u32 adc_clk_khz)
>>>  		return 0;
>>>  	}
>>>  
>>> +	/* Touchscreen Switches Closure time needed for allowing the value to
>>> +	 * stabilize.
>>> +	 * Switch Closure Time = (TSSCTIM * 4) ADCClock periods
>>> +	 */
>>> +	tssctim = DIV_ROUND_UP(TOUCH_SCTIM_US * adc_clk_khz / 1000, 4);
>>> +	dev_dbg(&idev->dev, "adc_clk at: %d KHz, tssctim at: %d\n",
>>> +		adc_clk_khz, tssctim);
>>> +
>>>  	if (st->touchscreen_type == ATMEL_ADC_TOUCHSCREEN_4WIRE)
>>>  		reg = AT91_ADC_TSMR_TSMODE_4WIRE_PRESS;
>>>  	else
>>>  		reg = AT91_ADC_TSMR_TSMODE_5WIRE;
>>>  
>>> +	reg |= AT91_ADC_TSMR_SCTIM_(tssctim) & AT91_ADC_TSMR_SCTIM;
>>>  	reg |= AT91_ADC_TSMR_TSAV_(st->caps->ts_filter_average)
>>>  	       & AT91_ADC_TSMR_TSAV;
>>>  	reg |= AT91_ADC_TSMR_PENDBC_(st->ts_pendbc) & AT91_ADC_TSMR_PENDBC;
>>>
>>
>>
> 
>