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

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Message-ID: <51aeb56b-c2f7-461f-065d-c581d3837340@atmel.com>
Date:   Mon, 5 Sep 2016 10:26:08 +0200
From:   Nicolas Ferre <nicolas.ferre@...el.com>
To:     Jonathan Cameron <jic23@...nel.org>,
        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

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,


>> ---
>>  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;
>>
> 
> 


-- 
Nicolas Ferre