iio: exynos-adc: add experimental touchscreen support

This adds support for the touchscreen on Samsung s3c64xx.
The driver is completely untested but shows roughly how
it could be done, following the example of the at91 driver.

compared to the old plat-samsung/adc driver, there is
no support for prioritizing ts over other clients, nor
for oversampling. From my reading of the code, the
priorities didn't actually have any effect at all, but
the oversampling might be needed.

Verifying this driver is the main issue that is currently
holding up multiplatform support for s3c64xx, so any help
in testing is very much appreciated.

The current version uses the IS_REACHABLE() that is
going to be introduced in the linux-media tree, please
comment this out for testing.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/arm/samsung/exynos-adc.txt

@@ -47,6 +47,9 @@ Required properties:
 
 - samsung,syscon-phandle Contains the PMU system controller node
 			(To access the ADC_PHY register on Exynos5250/5420/5800/3250)
+Optional properties:
+- has-touchscreen:	If present, indicates that a touchscreen is
+			connected an usable.
 
 Note: child nodes can be added for auto probing from device tree.
 

drivers/iio/adc/exynos_adc.c

@@ -35,6 +35,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/of_platform.h>
 #include <linux/err.h>
+#include <linux/input.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/machine.h>
@@ -42,12 +43,18 @@
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
 
+#include <linux/platform_data/touchscreen-s3c2410.h>
+
 /* S3C/EXYNOS4412/5250 ADC_V1 registers definitions */
 #define ADC_V1_CON(x)		((x) + 0x00)
+#define ADC_V1_TSC(x)		((x) + 0x04)
 #define ADC_V1_DLY(x)		((x) + 0x08)
 #define ADC_V1_DATX(x)		((x) + 0x0C)
+#define ADC_V1_DATY(x)		((x) + 0x10)
+#define ADC_V1_UPDN(x)		((x) + 0x14)
 #define ADC_V1_INTCLR(x)	((x) + 0x18)
 #define ADC_V1_MUX(x)		((x) + 0x1c)
+#define ADC_V1_CLRINTPNDNUP(x)	((x) + 0x20)
 
 /* S3C2410 ADC registers definitions */
 #define ADC_S3C2410_MUX(x)	((x) + 0x18)
@@ -71,6 +78,30 @@
 #define ADC_S3C2410_DATX_MASK	0x3FF
 #define ADC_S3C2416_CON_RES_SEL	(1u << 3)
 
+/* touch screen always uses channel 0 */
+#define ADC_S3C2410_MUX_TS	0
+
+/* ADCTSC Register Bits */
+#define ADC_S3C2443_TSC_UD_SEN		(1u << 8)
+#define ADC_S3C2410_TSC_YM_SEN		(1u << 7)
+#define ADC_S3C2410_TSC_YP_SEN		(1u << 6)
+#define ADC_S3C2410_TSC_XM_SEN		(1u << 5)
+#define ADC_S3C2410_TSC_XP_SEN		(1u << 4)
+#define ADC_S3C2410_TSC_PULL_UP_DISABLE	(1u << 3)
+#define ADC_S3C2410_TSC_AUTO_PST	(1u << 2)
+#define ADC_S3C2410_TSC_XY_PST(x)	(((x) & 0x3) << 0)
+
+#define ADC_TSC_WAIT4INT (ADC_S3C2410_TSC_YM_SEN | \
+			 ADC_S3C2410_TSC_YP_SEN | \
+			 ADC_S3C2410_TSC_XP_SEN | \
+			 ADC_S3C2410_TSC_XY_PST(3))
+
+#define ADC_TSC_AUTOPST	(ADC_S3C2410_TSC_YM_SEN | \
+			 ADC_S3C2410_TSC_YP_SEN | \
+			 ADC_S3C2410_TSC_XP_SEN | \
+			 ADC_S3C2410_TSC_AUTO_PST | \
+			 ADC_S3C2410_TSC_XY_PST(0))
+
 /* Bit definitions for ADC_V2 */
 #define ADC_V2_CON1_SOFT_RESET	(1u << 2)
 
@@ -88,7 +119,9 @@
 /* Bit definitions common for ADC_V1 and ADC_V2 */
 #define ADC_CON_EN_START	(1u << 0)
 #define ADC_CON_EN_START_MASK	(0x3 << 0)
+#define ADC_DATX_PRESSED	(1u << 15)
 #define ADC_DATX_MASK		0xFFF
+#define ADC_DATY_MASK		0xFFF
 
 #define EXYNOS_ADC_TIMEOUT	(msecs_to_jiffies(100))
 
@@ -98,17 +131,24 @@
 struct exynos_adc {
 	struct exynos_adc_data	*data;
 	struct device		*dev;
+	struct input_dev	*input;
 	void __iomem		*regs;
 	struct regmap		*pmu_map;
 	struct clk		*clk;
 	struct clk		*sclk;
 	unsigned int		irq;
+	unsigned int		tsirq;
+	unsigned int		delay;
 	struct regulator	*vdd;
 
 	struct completion	completion;
 
 	u32			value;
 	unsigned int            version;
+
+	bool			read_ts;
+	u32			ts_x;
+	u32			ts_y;
 };
 
 struct exynos_adc_data {
@@ -197,6 +237,9 @@ static void exynos_adc_v1_init_hw(struct exynos_adc *info)
 	/* Enable 12-bit ADC resolution */
 	con1 |= ADC_V1_CON_RES;
 	writel(con1, ADC_V1_CON(info->regs));
+
+	/* set touchscreen delay */
+	writel(info->delay, ADC_V1_DLY(info->regs));
 }
 
 static void exynos_adc_v1_exit_hw(struct exynos_adc *info)
@@ -480,8 +523,8 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
 	if (info->data->start_conv)
 		info->data->start_conv(info, chan->address);
 
-	timeout = wait_for_completion_timeout
-			(&info->completion, EXYNOS_ADC_TIMEOUT);
+	timeout = wait_for_completion_timeout(&info->completion,
+					      EXYNOS_ADC_TIMEOUT);
 	if (timeout == 0) {
 		dev_warn(&indio_dev->dev, "Conversion timed out! Resetting\n");
 		if (info->data->init_hw)
@@ -498,13 +541,55 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
 	return ret;
 }
 
+static int exynos_read_s3c64xx_ts(struct iio_dev *indio_dev, int *x, int *y)
+{
+	struct exynos_adc *info = iio_priv(indio_dev);
+	unsigned long timeout;
+	int ret;
+
+	mutex_lock(&indio_dev->mlock);
+	info->read_ts = true;
+
+	reinit_completion(&info->completion);
+
+	writel(ADC_S3C2410_TSC_PULL_UP_DISABLE | ADC_TSC_AUTOPST,
+	       ADC_V1_TSC(info->regs));
+
+	/* Select the ts channel to be used and Trigger conversion */
+	info->data->start_conv(info, ADC_S3C2410_MUX_TS);
+
+	timeout = wait_for_completion_timeout(&info->completion,
+					      EXYNOS_ADC_TIMEOUT);
+	if (timeout == 0) {
+		dev_warn(&indio_dev->dev, "Conversion timed out! Resetting\n");
+		if (info->data->init_hw)
+			info->data->init_hw(info);
+		ret = -ETIMEDOUT;
+	} else {
+		*x = info->ts_x;
+		*y = info->ts_y;
+		ret = 0;
+	}
+
+	info->read_ts = false;
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret;
+}
+
 static irqreturn_t exynos_adc_isr(int irq, void *dev_id)
 {
 	struct exynos_adc *info = (struct exynos_adc *)dev_id;
 	u32 mask = info->data->mask;
 
 	/* Read value */
+	if (info->read_ts) {
+		info->ts_x = readl(ADC_V1_DATX(info->regs));
+		info->ts_y = readl(ADC_V1_DATY(info->regs));
+		writel(ADC_TSC_WAIT4INT | ADC_S3C2443_TSC_UD_SEN, ADC_V1_TSC(info->regs));
+	} else {
 		info->value = readl(ADC_V1_DATX(info->regs)) & mask;
+	}
 
 	/* clear irq */
 	if (info->data->clear_irq)
@@ -515,6 +600,46 @@ static irqreturn_t exynos_adc_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+/*
+ * Here we (ab)use a threaded interrupt handler to stay running
+ * for as long as the touchscreen remains pressed, we report
+ * a new event with the latest data and then sleep until the
+ * next timer tick. This mirrors the behavior of the old
+ * driver, with much less code.
+ */
+static irqreturn_t exynos_ts_isr(int irq, void *dev_id)
+{
+	struct exynos_adc *info = dev_id;
+	struct iio_dev *dev = dev_get_drvdata(info->dev);
+	u32 x, y;
+	bool pressed;
+	int ret;
+
+	while (info->input->users) {
+		ret = exynos_read_s3c64xx_ts(dev, &x, &y);
+		if (ret == -ETIMEDOUT)
+			break;
+
+		pressed = x & y & ADC_DATX_PRESSED;
+		if (!pressed) {
+			input_report_key(info->input, BTN_TOUCH, 0);
+			input_sync(info->input);
+			break;
+		}
+
+		input_report_abs(info->input, ABS_X, x & ADC_DATX_MASK);
+		input_report_abs(info->input, ABS_Y, y & ADC_DATY_MASK);
+		input_report_key(info->input, BTN_TOUCH, 1);
+		input_sync(info->input);
+
+		msleep(1);
+	};
+
+	writel(0, ADC_V1_CLRINTPNDNUP(info->regs));
+
+	return IRQ_HANDLED;
+}
+
 static int exynos_adc_reg_access(struct iio_dev *indio_dev,
 			      unsigned reg, unsigned writeval,
 			      unsigned *readval)
@@ -566,18 +691,72 @@ static int exynos_adc_remove_devices(struct device *dev, void *c)
 	return 0;
 }
 
+static int exynos_adc_ts_open(struct input_dev *dev)
+{
+	struct exynos_adc *info = input_get_drvdata(dev);
+
+	enable_irq(info->tsirq);
+
+	return 0;
+}
+
+static void exynos_adc_ts_close(struct input_dev *dev)
+{
+	struct exynos_adc *info = input_get_drvdata(dev);
+
+	disable_irq(info->tsirq);
+}
+
+static int exynos_adc_ts_init(struct exynos_adc *info)
+{
+	int ret;
+
+	if (info->tsirq <= 0)
+		return -ENODEV;
+
+	info->input = input_allocate_device();
+	if (!info->input)
+		return -ENOMEM;
+
+	info->input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	info->input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+
+	input_set_abs_params(info->input, ABS_X, 0, 0x3FF, 0, 0);
+	input_set_abs_params(info->input, ABS_Y, 0, 0x3FF, 0, 0);
+
+	info->input->name = "S3C24xx TouchScreen";
+	info->input->id.bustype = BUS_HOST;
+	info->input->open = exynos_adc_ts_open;
+	info->input->close = exynos_adc_ts_close;
+
+	input_set_drvdata(info->input, info);
+
+	ret = input_register_device(info->input);
+	if (ret) {
+		input_free_device(info->input);
+		return ret;
+	}
+
+	disable_irq(info->tsirq);
+	ret = request_threaded_irq(info->tsirq, NULL, exynos_ts_isr,
+				   0, "touchscreen", info);
+	if (ret)
+		input_unregister_device(info->input);
+
+	return ret;
+}
+
 static int exynos_adc_probe(struct platform_device *pdev)
 {
 	struct exynos_adc *info = NULL;
 	struct device_node *np = pdev->dev.of_node;
+	struct s3c2410_ts_mach_info *pdata = dev_get_platdata(&pdev->dev);
 	struct iio_dev *indio_dev = NULL;
 	struct resource	*mem;
+	bool has_ts = false;
 	int ret = -ENODEV;
 	int irq;
 
-	if (!np)
-		return ret;
-
 	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(struct exynos_adc));
 	if (!indio_dev) {
 		dev_err(&pdev->dev, "failed allocating iio device\n");
@@ -613,8 +792,14 @@ static int exynos_adc_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "no irq resource?\n");
 		return irq;
 	}
-
 	info->irq = irq;
+
+	irq = platform_get_irq(pdev, 1);
+	if (irq == -EPROBE_DEFER)
+		return irq;
+
+	info->tsirq = irq;
+
 	info->dev = &pdev->dev;
 
 	init_completion(&info->completion);
@@ -680,6 +865,22 @@ static int exynos_adc_probe(struct platform_device *pdev)
 	if (info->data->init_hw)
 		info->data->init_hw(info);
 
+	/* leave out any TS related code if unreachable */
+	if (IS_REACHABLE(CONFIG_INPUT)) {
+		has_ts = of_property_read_bool(pdev->dev.of_node,
+					       "has-touchscreen") || pdata;
+	}
+
+	if (pdata)
+		info->delay = pdata->delay;
+	else
+		info->delay = 10000;
+
+	if (has_ts)
+		ret = exynos_adc_ts_init(info);
+	if (ret)
+		goto err_iio;
+
 	ret = of_platform_populate(np, exynos_adc_match, NULL, &indio_dev->dev);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed adding child nodes\n");
@@ -691,6 +892,11 @@ static int exynos_adc_probe(struct platform_device *pdev)
 err_of_populate:
 	device_for_each_child(&indio_dev->dev, NULL,
 				exynos_adc_remove_devices);
+	if (has_ts) {
+		input_unregister_device(info->input);
+		free_irq(info->tsirq, info);
+	}
+err_iio:
 	iio_device_unregister(indio_dev);
 err_irq:
 	free_irq(info->irq, info);
@@ -710,6 +916,10 @@ static int exynos_adc_remove(struct platform_device *pdev)
 	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
 	struct exynos_adc *info = iio_priv(indio_dev);
 
+	if (IS_REACHABLE(CONFIG_INPUT)) {
+		free_irq(info->tsirq, info);
+		input_unregister_device(info->input);
+	}
 	device_for_each_child(&indio_dev->dev, NULL,
 				exynos_adc_remove_devices);
 	iio_device_unregister(indio_dev);