iio: at91: introduce touch screen support in iio adc driver

AT91 ADC hardware integrate touch screen support. So this patch add touch
screen support for at91 adc iio driver.
To enable touch screen support in adc, you need to add the dt parameters:
  1. which type of touch are used? (4 or 5 wires), sample period time.
  2. correct pressure detect threshold value.

In the meantime, since touch screen will use a interal period trigger of adc,
so it is conflict to other hardware triggers. Driver will disable the hardware
trigger support if touch screen is enabled.

This driver has been tested in AT91SAM9X5-EK and SAMA5D3x-EK.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC: devicetree@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 364 insertions, 24 deletions

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 690a560e0da..17df74908db 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -11,6 +11,7 @@
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/io.h>
+#include <linux/input.h>
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
@@ -39,7 +40,23 @@
 #define at91_adc_writel(st, reg, val) \
 	(writel_relaxed(val, st->reg_base + reg))
 
+#define DRIVER_NAME		"at91_adc"
+#define MAX_POS_BITS		12
+
+#define TOUCH_SAMPLE_PERIOD_US		2000	/* 2ms */
+#define TOUCH_PEN_DETECT_DEBOUNCE_US	200
+
 struct at91_adc_caps {
+	bool	has_ts;		/* Support touch screen */
+	bool	has_tsmr;	/* only at91sam9x5, sama5d3 have TSMR reg */
+	/*
+	 * Numbers of sampling data will be averaged. Can be 0~3.
+	 * Hardware can average (2 ^ ts_filter_average) sample data.
+	 */
+	u8	ts_filter_average;
+	/* Pen Detection input pull-up resistor, can be 0~3 */
+	u8	ts_pen_detect_sensitivity;
+
 	/* startup time calculate function */
 	u32 (*calc_startup_ticks)(u8 startup_time, u32 adc_clk_khz);
 
@@ -47,6 +64,12 @@ struct at91_adc_caps {
 	struct at91_adc_reg_desc registers;
 };
 
+enum atmel_adc_ts_type {
+	ATMEL_ADC_TOUCHSCREEN_NONE = 0,
+	ATMEL_ADC_TOUCHSCREEN_4WIRE = 4,
+	ATMEL_ADC_TOUCHSCREEN_5WIRE = 5,
+};
+
 struct at91_adc_state {
 	struct clk		*adc_clk;
 	u16			*buffer;
@@ -71,6 +94,26 @@ struct at91_adc_state {
 	bool			low_res;	/* the resolution corresponds to the lowest one */
 	wait_queue_head_t	wq_data_avail;
 	struct at91_adc_caps	*caps;
+
+	/*
+	 * Following ADC channels are shared by touchscreen:
+	 *
+	 * CH0 -- Touch screen XP/UL
+	 * CH1 -- Touch screen XM/UR
+	 * CH2 -- Touch screen YP/LL
+	 * CH3 -- Touch screen YM/Sense
+	 * CH4 -- Touch screen LR(5-wire only)
+	 *
+	 * The bitfields below represents the reserved channel in the
+	 * touchscreen mode.
+	 */
+#define CHAN_MASK_TOUCHSCREEN_4WIRE	(0xf << 0)
+#define CHAN_MASK_TOUCHSCREEN_5WIRE	(0x1f << 0)
+	enum atmel_adc_ts_type	touchscreen_type;
+	struct input_dev	*ts_input;
+
+	u16			ts_sample_period_val;
+	u32			ts_pressure_threshold;
 };
 
 static irqreturn_t at91_adc_trigger_handler(int irq, void *p)
@@ -99,14 +142,10 @@ static irqreturn_t at91_adc_trigger_handler(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
-static irqreturn_t at91_adc_eoc_trigger(int irq, void *private)
+/* Handler for classic adc channel eoc trigger */
+void handle_adc_eoc_trigger(int irq, struct iio_dev *idev)
 {
-	struct iio_dev *idev = private;
 	struct at91_adc_state *st = iio_priv(idev);
-	u32 status = at91_adc_readl(st, st->registers->status_register);
-
-	if (!(status & st->registers->drdy_mask))
-		return IRQ_HANDLED;
 
 	if (iio_buffer_enabled(idev)) {
 		disable_irq_nosync(irq);
@@ -116,6 +155,115 @@ static irqreturn_t at91_adc_eoc_trigger(int irq, void *private)
 		st->done = true;
 		wake_up_interruptible(&st->wq_data_avail);
 	}
+}
+
+static int at91_ts_sample(struct at91_adc_state *st)
+{
+	unsigned int xscale, yscale, reg, z1, z2;
+	unsigned int x, y, pres, xpos, ypos;
+	unsigned int rxp = 1;
+	unsigned int factor = 1000;
+	struct iio_dev *idev = iio_priv_to_dev(st);
+
+	unsigned int xyz_mask_bits = st->res;
+	unsigned int xyz_mask = (1 << xyz_mask_bits) - 1;
+
+	/* calculate position */
+	/* x position = (x / xscale) * max, max = 2^MAX_POS_BITS - 1 */
+	reg = at91_adc_readl(st, AT91_ADC_TSXPOSR);
+	xpos = reg & xyz_mask;
+	x = (xpos << MAX_POS_BITS) - xpos;
+	xscale = (reg >> 16) & xyz_mask;
+	if (xscale == 0) {
+		dev_err(&idev->dev, "Error: xscale == 0!\n");
+		return -1;
+	}
+	x /= xscale;
+
+	/* y position = (y / yscale) * max, max = 2^MAX_POS_BITS - 1 */
+	reg = at91_adc_readl(st, AT91_ADC_TSYPOSR);
+	ypos = reg & xyz_mask;
+	y = (ypos << MAX_POS_BITS) - ypos;
+	yscale = (reg >> 16) & xyz_mask;
+	if (yscale == 0) {
+		dev_err(&idev->dev, "Error: yscale == 0!\n");
+		return -1;
+	}
+	y /= yscale;
+
+	/* calculate the pressure */
+	reg = at91_adc_readl(st, AT91_ADC_TSPRESSR);
+	z1 = reg & xyz_mask;
+	z2 = (reg >> 16) & xyz_mask;
+
+	if (z1 != 0)
+		pres = rxp * (x * factor / 1024) * (z2 * factor / z1 - factor)
+			/ factor;
+	else
+		pres = st->ts_pressure_threshold;	/* no pen contacted */
+
+	dev_dbg(&idev->dev, "xpos = %d, xscale = %d, ypos = %d, yscale = %d, z1 = %d, z2 = %d, press = %d\n",
+				xpos, xscale, ypos, yscale, z1, z2, pres);
+
+	if (pres < st->ts_pressure_threshold) {
+		dev_dbg(&idev->dev, "x = %d, y = %d, pressure = %d\n",
+					x, y, pres / factor);
+		input_report_abs(st->ts_input, ABS_X, x);
+		input_report_abs(st->ts_input, ABS_Y, y);
+		input_report_abs(st->ts_input, ABS_PRESSURE, pres);
+		input_report_key(st->ts_input, BTN_TOUCH, 1);
+		input_sync(st->ts_input);
+	} else {
+		dev_dbg(&idev->dev, "pressure too low: not reporting\n");
+	}
+
+	return 0;
+}
+
+static irqreturn_t at91_adc_interrupt(int irq, void *private)
+{
+	struct iio_dev *idev = private;
+	struct at91_adc_state *st = iio_priv(idev);
+	u32 status = at91_adc_readl(st, st->registers->status_register);
+	const uint32_t ts_data_irq_mask =
+		AT91_ADC_IER_XRDY |
+		AT91_ADC_IER_YRDY |
+		AT91_ADC_IER_PRDY;
+
+	if (status & st->registers->drdy_mask)
+		handle_adc_eoc_trigger(irq, idev);
+
+	if (status & AT91_ADC_IER_PEN) {
+		at91_adc_writel(st, AT91_ADC_IDR, AT91_ADC_IER_PEN);
+		at91_adc_writel(st, AT91_ADC_IER, AT91_ADC_IER_NOPEN |
+			ts_data_irq_mask);
+		/* Set up period trigger for sampling */
+		at91_adc_writel(st, st->registers->trigger_register,
+			AT91_ADC_TRGR_MOD_PERIOD_TRIG |
+			AT91_ADC_TRGR_TRGPER_(st->ts_sample_period_val));
+	} else if (status & AT91_ADC_IER_NOPEN) {
+		at91_adc_writel(st, st->registers->trigger_register, 0);
+		at91_adc_writel(st, AT91_ADC_IDR, AT91_ADC_IER_NOPEN |
+			ts_data_irq_mask);
+		at91_adc_writel(st, AT91_ADC_IER, AT91_ADC_IER_PEN);
+
+		input_report_key(st->ts_input, BTN_TOUCH, 0);
+		input_sync(st->ts_input);
+	} else if ((status & ts_data_irq_mask) == ts_data_irq_mask) {
+		/* Now all touchscreen data is ready */
+
+		if (status & AT91_ADC_ISR_PENS) {
+			/* validate data by pen contact */
+			at91_ts_sample(st);
+		} else {
+			/* triggered by event that is no pen contact, just read
+			 * them to clean the interrupt and discard all.
+			 */
+			at91_adc_readl(st, AT91_ADC_TSXPOSR);
+			at91_adc_readl(st, AT91_ADC_TSYPOSR);
+			at91_adc_readl(st, AT91_ADC_TSPRESSR);
+		}
+	}
 
 	return IRQ_HANDLED;
 }
@@ -125,6 +273,16 @@ static int at91_adc_channel_init(struct iio_dev *idev)
 	struct at91_adc_state *st = iio_priv(idev);
 	struct iio_chan_spec *chan_array, *timestamp;
 	int bit, idx = 0;
+	unsigned long rsvd_mask = 0;
+
+	/* If touchscreen is enable, then reserve the adc channels */
+	if (st->touchscreen_type == ATMEL_ADC_TOUCHSCREEN_4WIRE)
+		rsvd_mask = CHAN_MASK_TOUCHSCREEN_4WIRE;
+	else if (st->touchscreen_type == ATMEL_ADC_TOUCHSCREEN_5WIRE)
+		rsvd_mask = CHAN_MASK_TOUCHSCREEN_5WIRE;
+
+	/* set up the channel mask to reserve touchscreen channels */
+	st->channels_mask &= ~rsvd_mask;
 
 	idev->num_channels = bitmap_weight(&st->channels_mask,
 					   st->num_channels) + 1;
@@ -473,6 +631,39 @@ static u32 calc_startup_ticks_9x5(u8 startup_time, u32 adc_clk_khz)
 
 static const struct of_device_id at91_adc_dt_ids[];
 
+static int at91_adc_probe_dt_ts(struct device_node *node,
+	struct at91_adc_state *st, struct device *dev)
+{
+	int ret;
+	u32 prop;
+
+	ret = of_property_read_u32(node, "atmel,adc-ts-wires", &prop);
+	if (ret) {
+		dev_info(dev, "ADC Touch screen is disabled.\n");
+		return 0;
+	}
+
+	switch (prop) {
+	case 4:
+	case 5:
+		st->touchscreen_type = prop;
+		break;
+	default:
+		dev_err(dev, "Unsupported number of touchscreen wires (%d). Should be 4 or 5.\n", prop);
+		return -EINVAL;
+	}
+
+	prop = 0;
+	of_property_read_u32(node, "atmel,adc-ts-pressure-threshold", &prop);
+	st->ts_pressure_threshold = prop;
+	if (st->ts_pressure_threshold) {
+		return 0;
+	} else {
+		dev_err(dev, "Invalid pressure threshold for the touchscreen\n");
+		return -EINVAL;
+	}
+}
+
 static int at91_adc_probe_dt(struct at91_adc_state *st,
 			     struct platform_device *pdev)
 {
@@ -554,6 +745,12 @@ static int at91_adc_probe_dt(struct at91_adc_state *st,
 		i++;
 	}
 
+	/* Check if touchscreen is supported. */
+	if (st->caps->has_ts)
+		return at91_adc_probe_dt_ts(node, st, &idev->dev);
+	else
+		dev_info(&idev->dev, "not support touchscreen in the adc compatible string.\n");
+
 	return 0;
 
 error_ret:
@@ -585,6 +782,114 @@ static const struct iio_info at91_adc_info = {
 	.read_raw = &at91_adc_read_raw,
 };
 
+/* Touchscreen related functions */
+static int atmel_ts_open(struct input_dev *dev)
+{
+	struct at91_adc_state *st = input_get_drvdata(dev);
+
+	at91_adc_writel(st, AT91_ADC_IER, AT91_ADC_IER_PEN);
+	return 0;
+}
+
+static void atmel_ts_close(struct input_dev *dev)
+{
+	struct at91_adc_state *st = input_get_drvdata(dev);
+
+	at91_adc_writel(st, AT91_ADC_IDR, AT91_ADC_IER_PEN);
+}
+
+static int at91_ts_hw_init(struct at91_adc_state *st, u32 adc_clk_khz)
+{
+	u32 reg = 0, pendbc;
+	int i = 0;
+
+	if (st->touchscreen_type == ATMEL_ADC_TOUCHSCREEN_4WIRE)
+		reg = AT91_ADC_TSMR_TSMODE_4WIRE_PRESS;
+	else
+		reg = AT91_ADC_TSMR_TSMODE_5WIRE;
+
+	/* a Pen Detect Debounce Time is necessary for the ADC Touch to avoid
+	 * pen detect noise.
+	 * The formula is : Pen Detect Debounce Time = (2 ^ pendbc) / ADCClock
+	 */
+	pendbc = round_up(TOUCH_PEN_DETECT_DEBOUNCE_US * adc_clk_khz / 1000, 1);
+
+	while (pendbc >> ++i)
+		;	/* Empty! Find the shift offset */
+	if (abs(pendbc - (1 << i)) < abs(pendbc - (1 << (i - 1))))
+		pendbc = i;
+	else
+		pendbc = i - 1;
+
+	if (st->caps->has_tsmr) {
+		reg |= AT91_ADC_TSMR_TSAV_(st->caps->ts_filter_average)
+				& AT91_ADC_TSMR_TSAV;
+		reg |= AT91_ADC_TSMR_PENDBC_(pendbc) & AT91_ADC_TSMR_PENDBC;
+		reg |= AT91_ADC_TSMR_NOTSDMA;
+		reg |= AT91_ADC_TSMR_PENDET_ENA;
+		reg |= 0x03 << 8;	/* TSFREQ, need bigger than TSAV */
+
+		at91_adc_writel(st, AT91_ADC_TSMR, reg);
+	} else {
+		/* TODO: for 9g45 which has no TSMR */
+	}
+
+	/* Change adc internal resistor value for better pen detection,
+	 * default value is 100 kOhm.
+	 * 0 = 200 kOhm, 1 = 150 kOhm, 2 = 100 kOhm, 3 = 50 kOhm
+	 * option only available on ES2 and higher
+	 */
+	at91_adc_writel(st, AT91_ADC_ACR, st->caps->ts_pen_detect_sensitivity
+			& AT91_ADC_ACR_PENDETSENS);
+
+	/* Sample Peroid Time = (TRGPER + 1) / ADCClock */
+	st->ts_sample_period_val = round_up((TOUCH_SAMPLE_PERIOD_US *
+			adc_clk_khz / 1000) - 1, 1);
+
+	return 0;
+}
+
+static int at91_ts_register(struct at91_adc_state *st,
+		struct platform_device *pdev)
+{
+	struct input_dev *input;
+	struct iio_dev *idev = iio_priv_to_dev(st);
+	int ret;
+
+	input = input_allocate_device();
+	if (!input) {
+		dev_err(&idev->dev, "Failed to allocate TS device!\n");
+		return -ENOMEM;
+	}
+
+	input->name = DRIVER_NAME;
+	input->id.bustype = BUS_HOST;
+	input->dev.parent = &pdev->dev;
+	input->open = atmel_ts_open;
+	input->close = atmel_ts_close;
+
+	__set_bit(EV_ABS, input->evbit);
+	__set_bit(EV_KEY, input->evbit);
+	__set_bit(BTN_TOUCH, input->keybit);
+	input_set_abs_params(input, ABS_X, 0, (1 << MAX_POS_BITS) - 1, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, (1 << MAX_POS_BITS) - 1, 0, 0);
+	input_set_abs_params(input, ABS_PRESSURE, 0, 0xffffff, 0, 0);
+
+	st->ts_input = input;
+	input_set_drvdata(input, st);
+
+	ret = input_register_device(input);
+	if (ret)
+		input_free_device(st->ts_input);
+
+	return ret;
+}
+
+static void at91_ts_unregister(struct at91_adc_state *st)
+{
+	input_unregister_device(st->ts_input);
+}
+
 static int at91_adc_probe(struct platform_device *pdev)
 {
 	unsigned int prsc, mstrclk, ticks, adc_clk, adc_clk_khz, shtim;
@@ -636,7 +941,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 	at91_adc_writel(st, AT91_ADC_CR, AT91_ADC_SWRST);
 	at91_adc_writel(st, AT91_ADC_IDR, 0xFFFFFFFF);
 	ret = request_irq(st->irq,
-			  at91_adc_eoc_trigger,
+			  at91_adc_interrupt,
 			  0,
 			  pdev->dev.driver->name,
 			  idev);
@@ -681,6 +986,10 @@ static int at91_adc_probe(struct platform_device *pdev)
 	mstrclk = clk_get_rate(st->clk);
 	adc_clk = clk_get_rate(st->adc_clk);
 	adc_clk_khz = adc_clk / 1000;
+
+	dev_dbg(&pdev->dev, "Master clock is set as: %d Hz, adc_clk should set as: %d Hz\n",
+		mstrclk, adc_clk);
+
 	prsc = (mstrclk / (2 * adc_clk)) - 1;
 
 	if (!st->startup_time) {
@@ -717,30 +1026,52 @@ static int at91_adc_probe(struct platform_device *pdev)
 	init_waitqueue_head(&st->wq_data_avail);
 	mutex_init(&st->lock);
 
-	ret = at91_adc_buffer_init(idev);
-	if (ret < 0) {
-		dev_err(&pdev->dev, "Couldn't initialize the buffer.\n");
-		goto error_disable_adc_clk;
-	}
+	/*
+	 * Since touch screen will set trigger register as period trigger. So
+	 * when touch screen is enabled, then we have to disable hardware
+	 * trigger for classic adc.
+	 */
+	if (!st->touchscreen_type) {
+		ret = at91_adc_buffer_init(idev);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "Couldn't initialize the buffer.\n");
+			goto error_disable_adc_clk;
+		}
 
-	ret = at91_adc_trigger_init(idev);
-	if (ret < 0) {
-		dev_err(&pdev->dev, "Couldn't setup the triggers.\n");
-		goto error_unregister_buffer;
+		ret = at91_adc_trigger_init(idev);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "Couldn't setup the triggers.\n");
+			at91_adc_buffer_remove(idev);
+			goto error_disable_adc_clk;
+		}
+	} else {
+		if (!st->caps->has_tsmr) {
+			dev_err(&pdev->dev, "We don't support non-TSMR adc\n");
+			goto error_disable_adc_clk;
+		}
+
+		ret = at91_ts_register(st, pdev);
+		if (ret)
+			goto error_disable_adc_clk;
+
+		at91_ts_hw_init(st, adc_clk_khz);
 	}
 
 	ret = iio_device_register(idev);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Couldn't register the device.\n");
-		goto error_remove_triggers;
+		goto error_iio_device_register;
 	}
 
 	return 0;
 
-error_remove_triggers:
-	at91_adc_trigger_remove(idev);
-error_unregister_buffer:
-	at91_adc_buffer_remove(idev);
+error_iio_device_register:
+	if (!st->touchscreen_type) {
+		at91_adc_trigger_remove(idev);
+		at91_adc_buffer_remove(idev);
+	} else {
+		at91_ts_unregister(st);
+	}
 error_disable_adc_clk:
 	clk_disable_unprepare(st->adc_clk);
 error_disable_clk:
@@ -756,8 +1087,12 @@ static int at91_adc_remove(struct platform_device *pdev)
 	struct at91_adc_state *st = iio_priv(idev);
 
 	iio_device_unregister(idev);
-	at91_adc_trigger_remove(idev);
-	at91_adc_buffer_remove(idev);
+	if (!st->touchscreen_type) {
+		at91_adc_trigger_remove(idev);
+		at91_adc_buffer_remove(idev);
+	} else {
+		at91_ts_unregister(st);
+	}
 	clk_disable_unprepare(st->adc_clk);
 	clk_disable_unprepare(st->clk);
 	free_irq(st->irq, idev);
@@ -780,6 +1115,7 @@ static struct at91_adc_caps at91sam9260_caps = {
 };
 
 static struct at91_adc_caps at91sam9g45_caps = {
+	.has_ts = true,
 	.calc_startup_ticks = calc_startup_ticks_9260,	/* same as 9260 */
 	.num_channels = 8,
 	.registers = {
@@ -793,6 +1129,10 @@ static struct at91_adc_caps at91sam9g45_caps = {
 };
 
 static struct at91_adc_caps at91sam9x5_caps = {
+	.has_ts = true,
+	.has_tsmr = true,
+	.ts_filter_average = 3,
+	.ts_pen_detect_sensitivity = 2,
 	.calc_startup_ticks = calc_startup_ticks_9x5,
 	.num_channels = 12,
 	.registers = {
@@ -819,7 +1159,7 @@ static struct platform_driver at91_adc_driver = {
 	.probe = at91_adc_probe,
 	.remove = at91_adc_remove,
 	.driver = {
-		   .name = "at91_adc",
+		   .name = DRIVER_NAME,
 		   .of_match_table = of_match_ptr(at91_adc_dt_ids),
 	},
 };