Input: elants_i2c - wire up regulator support

-----Original Message-----
From: Dmitry Torokhov [mailto:[email protected]]
Sent: Thursday, August 06, 2015 2:54 AM
To: [email protected]
Cc: Rob Herring; Mark Rutland; Benson Leung; Duson Lin; Scott Liu; James Chen; [email protected]; [email protected]; [email protected]
Subject: [PATCH] Input: elants_i2c - wire up regulator support

Elan touchscreen controllers use two power supplies, vcc33 and vccio, and we need to enable them before trying to access the device. On X86 firmware usually does this, but on ARM it is usually left to the kernel.

Signed-off-by Dmitry Torokhov <[email protected]>

Reviewed-by Benson Leung <[email protected]>

Signed-off-by Dmitry Torokhov <[email protected]>

---
 .../devicetree/bindings/input/elants_i2c.txt       |   3 +
 drivers/input/touchscreen/elants_i2c.c             | 184
++++++++++++++++++---
 2 files changed, 165 insertions(+), 22 deletions(-)

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

index a765232..8a71038 100644

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

 [1]: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

drivers/input/touchscreen/elants_i2c.c +10 -0

index 42e43f1..1912265 100644
@@ -38,6 +38,8 @@
 #include <linux/input/mt.h>
 #include <linux/acpi.h>
 #include <linux/of.h>
+#include <linux/gpio/consumer.h>
+#include <linux/regulator/consumer.h>
 #include <asm/unaligned.h>
 
 /* Device, Driver information */

@@ -102,6 +104,9 @@
 /* calibration timeout definition */
 #define ELAN_CALI_TIMEOUT_MSEC	10000
 
+#define ELAN_POWERON_DELAY_USEC	500
+#define ELAN_RESET_DELAY_MSEC	20
+
 enum elants_state {
 	ELAN_STATE_NORMAL,
 	ELAN_WAIT_QUEUE_HEADER,

@@ -118,6 +123,10 @@ struct elants_data {
 	struct i2c_client *client;
 	struct input_dev *input;
 
+	struct regulator *vcc33;
+	struct regulator *vccio;
+	struct gpio_desc *reset_gpio;
+
 	u16 fw_version;
 	u8 test_version;
 	u8 solution_version;

@@ -141,6 +150,7 @@ struct elants_data {
 	u8 buf[MAX_PACKET_SIZE];
 
 	bool wake_irq_enabled;
+	bool keep_power_in_suspend;
 };
 
 static int elants_i2c_send(struct i2c_client *client, @@ -1058,6 +1068,67

@@ static void elants_i2c_remove_sysfs_group(void *_data)
sysfs_remove_group(&ts->client->dev.kobj,
&elants_attribute_group); }

drivers/input/touchscreen/elants_i2c.c +59 -7

+static int elants_i2c_power_on(struct elants_data *ts) {
+	int error;
+
+	/*
+	 * If we do not have reset gpio assume platform firmware
+	 * controls regulators and does power them on for us.
+	 */
+	if (IS_ERR_OR_NULL(ts->reset_gpio))
+		return 0;
+
+	gpiod_set_value_cansleep(ts->reset_gpio, 1);
+
+	error = regulator_enable(ts->vcc33);
+	if (error) {
+		dev_err(&ts->client->dev,
+			"failed to enable vcc33 regulator: %d\n",
+			error);
+		goto release_reset_gpio;
+	}
+
+	error = regulator_enable(ts->vccio);
+	if (error) {
+		dev_err(&ts->client->dev,
+			"failed to enable vccio regulator: %d\n",
+			error);
+		regulator_disable(ts->vcc33);
+		goto release_reset_gpio;
+	}
+
+	/*
+	 * We need to wait a bit after powering on controller before
+	 * we are allowed to release reset GPIO.
+	 */
+	udelay(ELAN_POWERON_DELAY_USEC);
+
+release_reset_gpio:
+	gpiod_set_value_cansleep(ts->reset_gpio, 0);
+	if (error)
+		return error;
+
+	msleep(ELAN_RESET_DELAY_MSEC);
+
+	return 0;
+}
+
+static void elants_i2c_power_off(void *_data) {
+	struct elants_data *ts = _data;
+
+	if (!IS_ERR_OR_NULL(ts->reset_gpio)) {
+		/*
+		 * Activate reset gpio to prevent leakage through the
+		 * pin once we shut off power to the controller.
+		 */
+		gpiod_set_value_cansleep(ts->reset_gpio, 1);
+		regulator_disable(ts->vccio);
+		regulator_disable(ts->vcc33);
+	}
+}
+
 static int elants_i2c_probe(struct i2c_client *client,
 			    const struct i2c_device_id *id)
 {

@@ -1072,13 +1143,6 @@ static int elants_i2c_probe(struct i2c_client
 *client,
 		return -ENXIO;
 	}
 
-	/* Make sure there is something at this address */
-	if (i2c_smbus_xfer(client->adapter, client->addr, 0,
-			I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy) < 0) {
-		dev_err(&client->dev, "nothing at this address\n");
-		return -ENXIO;
-	}
-
 	ts = devm_kzalloc(&client->dev, sizeof(struct elants_data),
 GFP_KERNEL);

drivers/input/touchscreen/elants_i2c.c +27 -0

 	if (!ts)
 		return -ENOMEM;

@@ -1089,6 +1153,70 @@ static int elants_i2c_probe(struct i2c_client
 *client,
 	ts->client = client;
 	i2c_set_clientdata(client, ts);
 
+	ts->vcc33 = devm_regulator_get(&client->dev, "vcc33");
+	if (IS_ERR(ts->vcc33)) {
+		error = PTR_ERR(ts->vcc33);
+		if (error != -EPROBE_DEFER)
+			dev_err(&client->dev,
+				"Failed to get 'vcc33' regulator: %d\n",
+				error);
+		return error;
+	}
+
+	ts->vccio = devm_regulator_get(&client->dev, "vccio");
+	if (IS_ERR(ts->vccio)) {
+		error = PTR_ERR(ts->vccio);
+		if (error != -EPROBE_DEFER)
+			dev_err(&client->dev,
+				"Failed to get 'vccio' regulator: %d\n",
+				error);
+		return error;
+	}
+
+	ts->reset_gpio = devm_gpiod_get(&client->dev, "reset");
+	if (IS_ERR(ts->reset_gpio)) {
+		error = PTR_ERR(ts->reset_gpio);
+
+		if (error == -EPROBE_DEFER)
+			return error;
+

drivers/input/touchscreen/elants_i2c.c +18 -0

+	if (error)
+		return error;
+
+	error = devm_add_action(&client->dev, elants_i2c_power_off, ts);
+	if (error) {
+		dev_err(&client->dev,
+			"failed to install power off action: %d\n", error);
+		elants_i2c_power_off(ts);
+		return error;
+	}
+
+	/* Make sure there is something at this address */
+	if (i2c_smbus_xfer(client->adapter, client->addr, 0,
+			   I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy) < 0) {
+		dev_err(&client->dev, "nothing at this address\n");
+		return -ENXIO;
+	}
+
 	error = elants_i2c_initialize(ts);
 	if (error) {

dev_err(&client->dev, "failed to initialize: %d\n", error);

-1196,17 +1324,23 @@ static int __maybe_unused elants_i2c_suspend(struct device *dev)

drivers/input/touchscreen/elants_i2c.c +0 -3

 	disable_irq(client->irq);
 
-	for (retry_cnt = 0; retry_cnt < MAX_RETRIES; retry_cnt++) {
-		error = elants_i2c_send(client, set_sleep_cmd,
-					sizeof(set_sleep_cmd));

drivers/input/touchscreen/elants_i2c.c +21 -9

-	}
+			dev_err(&client->dev,
+				"suspend command failed: %d\n", error);
+		}
 
-	if (device_may_wakeup(dev))
-		ts->wake_irq_enabled = (enable_irq_wake(client->irq) == 0);
+		if (device_may_wakeup(dev))
+			ts->wake_irq_enabled =
+					(enable_irq_wake(client->irq) == 0);
+	} else {
+		elants_i2c_power_off(ts);
+	}
 
 	return 0;
 }

@@ -1222,13 +1356,19 @@ static int __maybe_unused
 elants_i2c_resume(struct device *dev)
 	if (device_may_wakeup(dev) && ts->wake_irq_enabled)
 		disable_irq_wake(client->irq);
 
-	for (retry_cnt = 0; retry_cnt < MAX_RETRIES; retry_cnt++) {
-		error = elants_i2c_send(client, set_active_cmd,
-					sizeof(set_active_cmd));
-		if (!error)
-			break;
+	if (ts->keep_power_in_suspend) {
+		for (retry_cnt = 0; retry_cnt < MAX_RETRIES; retry_cnt++) {
+			error = elants_i2c_send(client, set_active_cmd,
+						sizeof(set_active_cmd));
+			if (!error)
+				break;
 
-		dev_err(&client->dev, "resume command failed: %d\n", error);
+			dev_err(&client->dev,
+				"resume command failed: %d\n", error);
+		}
+	} else {
+		elants_i2c_power_on(ts);
+		elants_i2c_initialize(ts);
 	}
 

ts->state = ELAN_STATE_NORMAL;
--
2.5.0.rc2.392.g76e840b

--
Dmitry

Hi Dmitry

I am curious about how reset gpio works and I think the reset gpio
at low level after elants_i2c_power_on(),
So that the controller won't response anyway, please see below my
question and correct me if I am wrong.

Quoted 28 lines

-----Original Message-----
From: Dmitry Torokhov [mailto:[email protected]]
Sent: Thursday, August 06, 2015 2:54 AM
To: [email protected]
Cc: Rob Herring; Mark Rutland; Benson Leung; Duson Lin; Scott Liu; James Chen; [email protected]; [email protected]; [email protected]
Subject: [PATCH] Input: elants_i2c - wire up regulator support

Elan touchscreen controllers use two power supplies, vcc33 and vccio, and we need to enable them before trying to access the device. On X86 firmware usually does this, but on ARM it is usually left to the kernel.

Signed-off-by Dmitry Torokhov <[email protected]>

Reviewed-by Benson Leung <[email protected]>

Signed-off-by Dmitry Torokhov <[email protected]>

---
 .../devicetree/bindings/input/elants_i2c.txt       |   3 +
 drivers/input/touchscreen/elants_i2c.c             | 184
++++++++++++++++++---
 2 files changed, 165 insertions(+), 22 deletions(-)

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

index a765232..8a71038 100644

Documentation/devicetree/bindings/input/elants_i2c.txt Optional properties: · line 20

Quoted 8 lines

Documentation/devicetree/bindings/input/elants_i2c.txt +3 -0

@@ -13,6 +13,9 @@ Optional properties:
 - pinctrl-names: should be "default" (see pinctrl binding [1]).
 - pinctrl-0: a phandle pointing to the pin settings for the device (see
   pinctrl binding [1]).
+- reset-gpios: reset gpio the chip is connected to.
+- vcc33-supply: a phandle for the regulator supplying 3.3V power.
+- vccio-supply: a phandle for the regulator supplying IO power.
 
 [0]:

Documentation/devicetree/bindings/interrupt-controller/interrupts.txt

Quoted 162 lines

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

 [1]: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

drivers/input/touchscreen/elants_i2c.c +10 -0

index 42e43f1..1912265 100644
@@ -38,6 +38,8 @@
 #include <linux/input/mt.h>
 #include <linux/acpi.h>
 #include <linux/of.h>
+#include <linux/gpio/consumer.h>
+#include <linux/regulator/consumer.h>
 #include <asm/unaligned.h>
 
 /* Device, Driver information */

@@ -102,6 +104,9 @@
 /* calibration timeout definition */
 #define ELAN_CALI_TIMEOUT_MSEC       10000
 
+#define ELAN_POWERON_DELAY_USEC      500
+#define ELAN_RESET_DELAY_MSEC        20
+
 enum elants_state {
      ELAN_STATE_NORMAL,
      ELAN_WAIT_QUEUE_HEADER,

@@ -118,6 +123,10 @@ struct elants_data {
      struct i2c_client *client;
      struct input_dev *input;
 
+     struct regulator *vcc33;
+     struct regulator *vccio;
+     struct gpio_desc *reset_gpio;
+
      u16 fw_version;
      u8 test_version;
      u8 solution_version;

@@ -141,6 +150,7 @@ struct elants_data {
      u8 buf[MAX_PACKET_SIZE];
 
      bool wake_irq_enabled;
+     bool keep_power_in_suspend;
 };
 
 static int elants_i2c_send(struct i2c_client *client, @@ -1058,6 +1068,67

@@ static void elants_i2c_remove_sysfs_group(void *_data)

      sysfs_remove_group(&ts->client->dev.kobj,

&elants_attribute_group); }

drivers/input/touchscreen/elants_i2c.c +59 -7

+static int elants_i2c_power_on(struct elants_data *ts) {
+     int error;
+
+     /*
+      * If we do not have reset gpio assume platform firmware
+      * controls regulators and does power them on for us.
+      */
+     if (IS_ERR_OR_NULL(ts->reset_gpio))
+             return 0;
+
+     gpiod_set_value_cansleep(ts->reset_gpio, 1);
+
+     error = regulator_enable(ts->vcc33);
+     if (error) {
+             dev_err(&ts->client->dev,
+                     "failed to enable vcc33 regulator: %d\n",
+                     error);
+             goto release_reset_gpio;
+     }
+
+     error = regulator_enable(ts->vccio);
+     if (error) {
+             dev_err(&ts->client->dev,
+                     "failed to enable vccio regulator: %d\n",
+                     error);
+             regulator_disable(ts->vcc33);
+             goto release_reset_gpio;
+     }
+
+     /*
+      * We need to wait a bit after powering on controller before
+      * we are allowed to release reset GPIO.
+      */
+     udelay(ELAN_POWERON_DELAY_USEC);
+
+release_reset_gpio:
+     gpiod_set_value_cansleep(ts->reset_gpio, 0);
+     if (error)
+             return error;
+
+     msleep(ELAN_RESET_DELAY_MSEC);
+
+     return 0;
+}
+
+static void elants_i2c_power_off(void *_data) {
+     struct elants_data *ts = _data;
+
+     if (!IS_ERR_OR_NULL(ts->reset_gpio)) {
+             /*
+              * Activate reset gpio to prevent leakage through the
+              * pin once we shut off power to the controller.
+              */
+             gpiod_set_value_cansleep(ts->reset_gpio, 1);
+             regulator_disable(ts->vccio);
+             regulator_disable(ts->vcc33);
+     }
+}
+
 static int elants_i2c_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)
 {

@@ -1072,13 +1143,6 @@ static int elants_i2c_probe(struct i2c_client
 *client,
              return -ENXIO;
      }
 
-     /* Make sure there is something at this address */
-     if (i2c_smbus_xfer(client->adapter, client->addr, 0,
-                     I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy) < 0) {
-             dev_err(&client->dev, "nothing at this address\n");
-             return -ENXIO;
-     }
-
      ts = devm_kzalloc(&client->dev, sizeof(struct elants_data),
 GFP_KERNEL);

      if (!ts)
              return -ENOMEM;

drivers/input/touchscreen/elants_i2c.c +31 -0

@@ -1089,6 +1153,70 @@ static int elants_i2c_probe(struct i2c_client
 *client,
      ts->client = client;
      i2c_set_clientdata(client, ts);
 
+     ts->vcc33 = devm_regulator_get(&client->dev, "vcc33");
+     if (IS_ERR(ts->vcc33)) {
+             error = PTR_ERR(ts->vcc33);
+             if (error != -EPROBE_DEFER)
+                     dev_err(&client->dev,
+                             "Failed to get 'vcc33' regulator: %d\n",
+                             error);
+             return error;
+     }
+
+     ts->vccio = devm_regulator_get(&client->dev, "vccio");
+     if (IS_ERR(ts->vccio)) {
+             error = PTR_ERR(ts->vccio);
+             if (error != -EPROBE_DEFER)
+                     dev_err(&client->dev,
+                             "Failed to get 'vccio' regulator: %d\n",
+                             error);
+             return error;
+     }
+
+     ts->reset_gpio = devm_gpiod_get(&client->dev, "reset");
+     if (IS_ERR(ts->reset_gpio)) {
+             error = PTR_ERR(ts->reset_gpio);
+
+             if (error == -EPROBE_DEFER)
+                     return error;
+
+             if (error != -ENOENT && error != -ENOSYS) {
+                     dev_err(&client->dev,
+                             "failed to get reset gpio: %d\n",
+                             error);

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client, · line 1192

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c +6 -0

+                     return error;
+             }
+
+             ts->keep_power_in_suspend = true;
+     } else {
+             error = gpiod_direction_output(ts->reset_gpio, 0);

Does it mean to reset our controller? (reset gpio pull low).

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client,

Quoted 4 lines

drivers/input/touchscreen/elants_i2c.c +3 -0

+             if (error) {
+                     dev_err(&client->dev,
+                             "failed to configure reset gpio as output:

%d\n",

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client, · line 1201

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c +6 -0

+                             error);
+                     return error;
+             }
+     }
+
+     error = elants_i2c_power_on(ts);

If reset gpio is at low, controller won't response initialize flow. I am curious that does reset pin be at low level after
elants_i2c_power_on(ts)?

-----Original Message-----
From: Dmitry Torokhov [mailto:[email protected]]
Sent: Friday, August 07, 2015 8:25 AM
To: ELAN 劉嘉駿
Cc: Dmitry Torokhov; [email protected]; Rob Herring; Mark Rutland; Benson Leung; Duson Lin; James Chen; [email protected]; lkml
Subject: Re: [PATCH] Input: elants_i2c - wire up regulator support

Hi Scott,

Quoted 158 lines · ELAN 劉嘉駿

Hi Dmitry

I am curious about how reset gpio works and I think the reset
gpio at low level after elants_i2c_power_on(),
So that the controller won't response anyway, please see below
my question and correct me if I am wrong.

Quoted 28 lines

-----Original Message-----
From: Dmitry Torokhov [mailto:[email protected]]
Sent: Thursday, August 06, 2015 2:54 AM
To: [email protected]
Cc: Rob Herring; Mark Rutland; Benson Leung; Duson Lin; Scott Liu; James Chen; [email protected]; [email protected]; [email protected]
Subject: [PATCH] Input: elants_i2c - wire up regulator support

Elan touchscreen controllers use two power supplies, vcc33 and vccio, and we need to enable them before trying to access the device. On X86 firmware usually does this, but on ARM it is usually left to the kernel.

Signed-off-by Dmitry Torokhov <[email protected]>

Reviewed-by Benson Leung <[email protected]>

Signed-off-by Dmitry Torokhov <[email protected]>

---
 .../devicetree/bindings/input/elants_i2c.txt       |   3 +
 drivers/input/touchscreen/elants_i2c.c             | 184
++++++++++++++++++---
 2 files changed, 165 insertions(+), 22 deletions(-)

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

index a765232..8a71038 100644

Documentation/devicetree/bindings/input/elants_i2c.txt Optional properties: · line 20

Quoted 8 lines

Documentation/devicetree/bindings/input/elants_i2c.txt +3 -0

@@ -13,6 +13,9 @@ Optional properties:
 - pinctrl-names: should be "default" (see pinctrl binding [1]).
 - pinctrl-0: a phandle pointing to the pin settings for the device (see
   pinctrl binding [1]).
+- reset-gpios: reset gpio the chip is connected to.
+- vcc33-supply: a phandle for the regulator supplying 3.3V power.
+- vccio-supply: a phandle for the regulator supplying IO power.
 
 [0]:

Documentation/devicetree/bindings/interrupt-controller/interrupts.txt

Quoted 114 lines

Documentation/devicetree/bindings/input/elants_i2c.txt +0 -0

 [1]: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

drivers/input/touchscreen/elants_i2c.c +11 -0

index 42e43f1..1912265 100644
@@ -38,6 +38,8 @@
 #include <linux/input/mt.h>
 #include <linux/acpi.h>
 #include <linux/of.h>
+#include <linux/gpio/consumer.h>
+#include <linux/regulator/consumer.h>
 #include <asm/unaligned.h>
 
 /* Device, Driver information */

@@ -102,6 +104,9 @@
 /* calibration timeout definition */
 #define ELAN_CALI_TIMEOUT_MSEC       10000
 
+#define ELAN_POWERON_DELAY_USEC      500
+#define ELAN_RESET_DELAY_MSEC        20
+
 enum elants_state {
      ELAN_STATE_NORMAL,
      ELAN_WAIT_QUEUE_HEADER,

@@ -118,6 +123,10 @@ struct elants_data {
      struct i2c_client *client;
      struct input_dev *input;
 
+     struct regulator *vcc33;
+     struct regulator *vccio;
+     struct gpio_desc *reset_gpio;
+
      u16 fw_version;
      u8 test_version;
      u8 solution_version;

@@ -141,6 +150,7 @@ struct elants_data {
      u8 buf[MAX_PACKET_SIZE];
 
      bool wake_irq_enabled;
+     bool keep_power_in_suspend;
 };
 
 static int elants_i2c_send(struct i2c_client *client, @@ -1058,6
+1068,67 @@ static void elants_i2c_remove_sysfs_group(void *_data)
      sysfs_remove_group(&ts->client->dev.kobj,

&elants_attribute_group); }

drivers/input/touchscreen/elants_i2c.c +59 -1

+static int elants_i2c_power_on(struct elants_data *ts) {
+     int error;
+
+     /*
+      * If we do not have reset gpio assume platform firmware
+      * controls regulators and does power them on for us.
+      */
+     if (IS_ERR_OR_NULL(ts->reset_gpio))
+             return 0;
+
+     gpiod_set_value_cansleep(ts->reset_gpio, 1);
+
+     error = regulator_enable(ts->vcc33);
+     if (error) {
+             dev_err(&ts->client->dev,
+                     "failed to enable vcc33 regulator: %d\n",
+                     error);
+             goto release_reset_gpio;
+     }
+
+     error = regulator_enable(ts->vccio);
+     if (error) {
+             dev_err(&ts->client->dev,
+                     "failed to enable vccio regulator: %d\n",
+                     error);
+             regulator_disable(ts->vcc33);
+             goto release_reset_gpio;
+     }
+
+     /*
+      * We need to wait a bit after powering on controller before
+      * we are allowed to release reset GPIO.
+      */
+     udelay(ELAN_POWERON_DELAY_USEC);
+
+release_reset_gpio:
+     gpiod_set_value_cansleep(ts->reset_gpio, 0);
+     if (error)
+             return error;
+
+     msleep(ELAN_RESET_DELAY_MSEC);
+
+     return 0;
+}
+
+static void elants_i2c_power_off(void *_data) {
+     struct elants_data *ts = _data;
+
+     if (!IS_ERR_OR_NULL(ts->reset_gpio)) {
+             /*
+              * Activate reset gpio to prevent leakage through the
+              * pin once we shut off power to the controller.
+              */
+             gpiod_set_value_cansleep(ts->reset_gpio, 1);
+             regulator_disable(ts->vccio);
+             regulator_disable(ts->vcc33);
+     }
+}
+
 static int elants_i2c_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)  { @@
-1072,13 +1143,6 @@ static int elants_i2c_probe(struct i2c_client

*client,

              return -ENXIO;
      }

Quoted 3 lines

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client,

Quoted 3 lines

drivers/input/touchscreen/elants_i2c.c +0 -3

-     /* Make sure there is something at this address */
-     if (i2c_smbus_xfer(client->adapter, client->addr, 0,
-                     I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE,

&dummy) < 0) {

Quoted 13 lines

Quoted 13 lines

drivers/input/touchscreen/elants_i2c.c +0 -4

-             dev_err(&client->dev, "nothing at this address\n");
-             return -ENXIO;
-     }
-
      ts = devm_kzalloc(&client->dev, sizeof(struct elants_data),

GFP_KERNEL);
      if (!ts)
              return -ENOMEM;

drivers/input/touchscreen/elants_i2c.c +0 -0

@@ -1089,6 +1153,70 @@ static int elants_i2c_probe(struct i2c_client
 *client,
      ts->client = client;
      i2c_set_clientdata(client, ts);
 

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client,

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c +6 -0

+     ts->vcc33 = devm_regulator_get(&client->dev, "vcc33");
+     if (IS_ERR(ts->vcc33)) {
+             error = PTR_ERR(ts->vcc33);
+             if (error != -EPROBE_DEFER)
+                     dev_err(&client->dev,
+                             "Failed to get 'vcc33' regulator:

%d\n",

Quoted 10 lines

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client,

Quoted 10 lines

drivers/input/touchscreen/elants_i2c.c +10 -0

+                             error);
+             return error;
+     }
+
+     ts->vccio = devm_regulator_get(&client->dev, "vccio");
+     if (IS_ERR(ts->vccio)) {
+             error = PTR_ERR(ts->vccio);
+             if (error != -EPROBE_DEFER)
+                     dev_err(&client->dev,
+                             "Failed to get 'vccio' regulator:

%d\n",

Quoted 15 lines

Quoted 15 lines

drivers/input/touchscreen/elants_i2c.c +15 -0

+                             error);
+             return error;
+     }
+
+     ts->reset_gpio = devm_gpiod_get(&client->dev, "reset");
+     if (IS_ERR(ts->reset_gpio)) {
+             error = PTR_ERR(ts->reset_gpio);
+
+             if (error == -EPROBE_DEFER)
+                     return error;
+
+             if (error != -ENOENT && error != -ENOSYS) {
+                     dev_err(&client->dev,
+                             "failed to get reset gpio: %d\n",
+                             error);

Quoted 8 lines

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client, · line 1192

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c +6 -0

+                     return error;
+             }
+
+             ts->keep_power_in_suspend = true;
+     } else {
+             error = gpiod_direction_output(ts->reset_gpio, 0);

Does it mean to reset our controller? (reset gpio pull low).

No, gpiod takes into account the declared polarity of the GPIO signal and we declare the reset GPIOs as "active low" in DTS. So here we configure GPIO for output and make it inactive (which translates to HIGH).

Quoted 4 lines

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client,

Quoted 4 lines

drivers/input/touchscreen/elants_i2c.c +3 -0

+             if (error) {
+                     dev_err(&client->dev,
+                             "failed to configure reset gpio as

output:

Quoted 11 lines

%d\n",

drivers/input/touchscreen/elants_i2c.c static int elants_i2c_probe(struct i2c_client *client, · line 1201

Quoted 6 lines

drivers/input/touchscreen/elants_i2c.c +6 -0

+                             error);
+                     return error;
+             }
+     }
+
+     error = elants_i2c_power_on(ts);

If reset gpio is at low, controller won't response initialize flow. I am curious that does reset pin be at low level after
elants_i2c_power_on(ts)?

The reset gpio will be "inactive", or logical 0. Given that we expect these gpios be declared as GPIO_ACTIVE_LOW this translates to line going HIGH->LOW->HIGH in elants_i2c_power_on() and stay HIGH while the driver is bound to the device.

Thanks.

--
Dmitry