Input: atmel_mxt_ts - support regulator supplies

This adds the code for the Atmel touchscreens such as mXT224 to obtain
power regulators for the supply voltages AVDD and VDD. On mobile phones
such as Samsung GT-I8190 (Golden) this is needed to explicitly bring power
online.

We just enable the regulators at probe() and disable them at remove()
or in the error path for now.

As regulators are naturally stubbed if not available, this should have no
impact on existing systems.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20201104153032.1387747-3-linus.walleij@linaro.orgSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/atmel_mxt_ts.c

@@ -24,6 +24,7 @@
 #include <linux/of.h>
 #include <linux/property.h>
 #include <linux/slab.h>
+#include <linux/regulator/consumer.h>
 #include <linux/gpio/consumer.h>
 #include <asm/unaligned.h>
 #include <media/v4l2-device.h>
@@ -309,6 +310,7 @@ struct mxt_data {
 	u8 multitouch;
 	struct t7_config t7_cfg;
 	struct mxt_dbg dbg;
+	struct regulator_bulk_data regulators[2];
 	struct gpio_desc *reset_gpio;
 	bool use_retrigen_workaround;
 
@@ -3134,6 +3136,21 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	if (error)
 		return error;
 
+	/*
+	 * VDDA is the analog voltage supply 2.57..3.47 V
+	 * VDD  is the digital voltage supply 1.71..3.47 V
+	 */
+	data->regulators[0].supply = "vdda";
+	data->regulators[1].supply = "vdd";
+	error = devm_regulator_bulk_get(&client->dev, ARRAY_SIZE(data->regulators),
+					data->regulators);
+	if (error) {
+		if (error != -EPROBE_DEFER)
+			dev_err(&client->dev, "Failed to get regulators %d\n",
+				error);
+		return error;
+	}
+
 	/* Request the RESET line as asserted so we go into reset */
 	data->reset_gpio = devm_gpiod_get_optional(&client->dev,
 						   "reset", GPIOD_OUT_HIGH);
@@ -3153,6 +3170,19 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
 
 	disable_irq(client->irq);
 
+	error = regulator_bulk_enable(ARRAY_SIZE(data->regulators),
+				      data->regulators);
+	if (error) {
+		dev_err(&client->dev, "failed to enable regulators: %d\n",
+			error);
+		return error;
+	}
+	/*
+	 * The device takes 40ms to come up after power-on according
+	 * to the mXT224 datasheet, page 13.
+	 */
+	msleep(MXT_BACKUP_TIME);
+
 	if (data->reset_gpio) {
 		/* Wait a while and then de-assert the RESET GPIO line */
 		msleep(MXT_RESET_GPIO_TIME);
@@ -3162,7 +3192,7 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
 
 	error = mxt_initialize(data);
 	if (error)
-		return error;
+		goto err_disable_regulators;
 
 	error = sysfs_create_group(&client->dev.kobj, &mxt_attr_group);
 	if (error) {
@@ -3176,6 +3206,9 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
 err_free_object:
 	mxt_free_input_device(data);
 	mxt_free_object_table(data);
+err_disable_regulators:
+	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
+			       data->regulators);
 	return error;
 }
 
@@ -3187,6 +3220,8 @@ static int mxt_remove(struct i2c_client *client)
 	sysfs_remove_group(&client->dev.kobj, &mxt_attr_group);
 	mxt_free_input_device(data);
 	mxt_free_object_table(data);
+	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
+			       data->regulators);
 
 	return 0;
 }