Input: add touchscreen support for TS-4800

On this board, the touchscreen, an ads7843, is not handled directly by
Linux but by a companion FPGA. This FPGA is memory-mapped and the IP
design is very similar to the mk712.

This commit adds the support for this IP.

Signed-off-by: Damien Riegel <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/touchscreen/ts4800-ts.txt

···
+* TS-4800 Touchscreen bindings
+
+Required properties:
+- compatible: must be "technologic,ts4800-ts"
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- syscon: phandle / integers array that points to the syscon node which
+          describes the FPGA's syscon registers.
+          - phandle to FPGA's syscon
+          - offset to the touchscreen register
+          - offset to the touchscreen enable bit

drivers/input/touchscreen/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called touchit213.
 
+config TOUCHSCREEN_TS4800
+	tristate "TS-4800 touchscreen"
+	depends on HAS_IOMEM && OF
+	select MFD_SYSCON
+	select INPUT_POLLDEV
+	help
+	  Say Y here if you have a touchscreen on a TS-4800 board.
+
+	  On TS-4800, the touchscreen is not handled directly by Linux but by
+	  a companion FPGA.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ts4800_ts.
+
 config TOUCHSCREEN_TSC_SERIO
 	tristate "TSC-10/25/40 serial touchscreen support"
 	select SERIO

drivers/input/touchscreen/Makefile

···
 obj-$(CONFIG_TOUCHSCREEN_TOUCHIT213)	+= touchit213.o
 obj-$(CONFIG_TOUCHSCREEN_TOUCHRIGHT)	+= touchright.o
 obj-$(CONFIG_TOUCHSCREEN_TOUCHWIN)	+= touchwin.o
+obj-$(CONFIG_TOUCHSCREEN_TS4800)	+= ts4800-ts.o
 obj-$(CONFIG_TOUCHSCREEN_TSC_SERIO)	+= tsc40.o
 obj-$(CONFIG_TOUCHSCREEN_TSC200X_CORE)	+= tsc200x-core.o
 obj-$(CONFIG_TOUCHSCREEN_TSC2004)	+= tsc2004.o

drivers/input/touchscreen/ts4800-ts.c

···
+/*
+ * Touchscreen driver for the TS-4800 board
+ *
+ * Copyright (c) 2015 - Savoir-faire Linux
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/bitops.h>
+#include <linux/input.h>
+#include <linux/input-polldev.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+/* polling interval in ms */
+#define POLL_INTERVAL		3
+
+#define DEBOUNCE_COUNT		1
+
+/* sensor values are 12-bit wide */
+#define MAX_12BIT		((1 << 12) - 1)
+
+#define PENDOWN_MASK		0x1
+
+#define X_OFFSET		0x0
+#define Y_OFFSET		0x2
+
+struct ts4800_ts {
+	struct input_polled_dev *poll_dev;
+	struct device           *dev;
+	char                    phys[32];
+
+	void __iomem            *base;
+	struct regmap           *regmap;
+	unsigned int            reg;
+	unsigned int            bit;
+
+	bool                    pendown;
+	int                     debounce;
+};
+
+static void ts4800_ts_open(struct input_polled_dev *dev)
+{
+	struct ts4800_ts *ts = dev->private;
+	int ret;
+
+	ts->pendown = false;
+	ts->debounce = DEBOUNCE_COUNT;
+
+	ret = regmap_update_bits(ts->regmap, ts->reg, ts->bit, ts->bit);
+	if (ret)
+		dev_warn(ts->dev, "Failed to enable touchscreen\n");
+}
+
+static void ts4800_ts_close(struct input_polled_dev *dev)
+{
+	struct ts4800_ts *ts = dev->private;
+	int ret;
+
+	ret = regmap_update_bits(ts->regmap, ts->reg, ts->bit, 0);
+	if (ret)
+		dev_warn(ts->dev, "Failed to disable touchscreen\n");
+
+}
+
+static void ts4800_ts_poll(struct input_polled_dev *dev)
+{
+	struct input_dev *input_dev = dev->input;
+	struct ts4800_ts *ts = dev->private;
+	u16 last_x = readw(ts->base + X_OFFSET);
+	u16 last_y = readw(ts->base + Y_OFFSET);
+	bool pendown = last_x & PENDOWN_MASK;
+
+	if (pendown) {
+		if (ts->debounce) {
+			ts->debounce--;
+			return;
+		}
+
+		if (!ts->pendown) {
+			input_report_key(input_dev, BTN_TOUCH, 1);
+			ts->pendown = true;
+		}
+
+		last_x = ((~last_x) >> 4) & MAX_12BIT;
+		last_y = ((~last_y) >> 4) & MAX_12BIT;
+
+		input_report_abs(input_dev, ABS_X, last_x);
+		input_report_abs(input_dev, ABS_Y, last_y);
+		input_sync(input_dev);
+	} else if (ts->pendown) {
+		ts->pendown = false;
+		ts->debounce = DEBOUNCE_COUNT;
+		input_report_key(input_dev, BTN_TOUCH, 0);
+		input_sync(input_dev);
+	}
+}
+
+static int ts4800_parse_dt(struct platform_device *pdev,
+			   struct ts4800_ts *ts)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *syscon_np;
+	u32 reg, bit;
+	int error;
+
+	syscon_np = of_parse_phandle(np, "syscon", 0);
+	if (!syscon_np) {
+		dev_err(dev, "no syscon property\n");
+		return -ENODEV;
+	}
+
+	error = of_property_read_u32_index(np, "syscon", 1, &reg);
+	if (error < 0) {
+		dev_err(dev, "no offset in syscon\n");
+		return error;
+	}
+
+	ts->reg = reg;
+
+	error = of_property_read_u32_index(np, "syscon", 2, &bit);
+	if (error < 0) {
+		dev_err(dev, "no bit in syscon\n");
+		return error;
+	}
+
+	ts->bit = BIT(bit);
+
+	ts->regmap = syscon_node_to_regmap(syscon_np);
+	if (IS_ERR(ts->regmap)) {
+		dev_err(dev, "cannot get parent's regmap\n");
+		return PTR_ERR(ts->regmap);
+	}
+
+	return 0;
+}
+
+static int ts4800_ts_probe(struct platform_device *pdev)
+{
+	struct input_polled_dev *poll_dev;
+	struct ts4800_ts *ts;
+	struct resource *res;
+	int error;
+
+	ts = devm_kzalloc(&pdev->dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	error = ts4800_parse_dt(pdev, ts);
+	if (error)
+		return error;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	ts->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(ts->base))
+		return PTR_ERR(ts->base);
+
+	poll_dev = devm_input_allocate_polled_device(&pdev->dev);
+	if (!poll_dev)
+		return -ENOMEM;
+
+	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&pdev->dev));
+	ts->poll_dev = poll_dev;
+	ts->dev = &pdev->dev;
+
+	poll_dev->private = ts;
+	poll_dev->poll_interval = POLL_INTERVAL;
+	poll_dev->open = ts4800_ts_open;
+	poll_dev->close = ts4800_ts_close;
+	poll_dev->poll = ts4800_ts_poll;
+
+	poll_dev->input->name = "TS-4800 Touchscreen";
+	poll_dev->input->phys = ts->phys;
+
+	input_set_capability(poll_dev->input, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(poll_dev->input, ABS_X, 0, MAX_12BIT, 0, 0);
+	input_set_abs_params(poll_dev->input, ABS_Y, 0, MAX_12BIT, 0, 0);
+
+	error = input_register_polled_device(poll_dev);
+	if (error) {
+		dev_err(&pdev->dev,
+			"Unabled to register polled input device (%d)\n",
+			error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id ts4800_ts_of_match[] = {
+	{ .compatible = "technologic,ts4800-ts", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ts4800_ts_of_match);
+
+static struct platform_driver ts4800_ts_driver = {
+	.driver = {
+		.name = "ts4800-ts",
+		.of_match_table = ts4800_ts_of_match,
+	},
+	.probe = ts4800_ts_probe,
+};
+module_platform_driver(ts4800_ts_driver);
+
+MODULE_AUTHOR("Damien Riegel <[e-mail]>");
+MODULE_DESCRIPTION("TS-4800 Touchscreen Driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:ts4800_ts");