[PATCH v3 0/3] Add Reset and Wakeup support for CCS811

[PATCH v3 0/3] Add Reset and Wakeup support for CCS811

[mani]

From: Manivannan Sadhasivam <mani@kernel.org>

Hello,

This patchset adds external reset and wakeup support for CCS811 VOC
gas sensor. The nRESET and nWAKE pins available on the device are
utilised to provide these functionalities.

The patchset has been validated using CCS811 connected to STM32MP1 based
board over I2C.

While at it, the devicetree yaml binding and OF match table for this sensor
are also added.

Thanks,
Mani

Changes in v3:

* Added ccs811_set_wake(false) to all error paths before calling it actually
* Added Andy's reviewed-by tag
* Added comment for reset procedure and dropped error print for gpio request

Changes in v2:

* Fixed DT binding schema and switched to dual license (GPL/BSD)
* Returned actual error code from devm_gpiod_get_optional()
* Dropped of.h include and of_match_ptr()

Manivannan Sadhasivam (3):
  iio: chemical: Add support for external Reset and Wakeup in CCS811
  iio: chemical: Add OF match table for CCS811 VOC sensor
  dt-bindings: serial: Add binding for software flow control in STM32
    UART

 .../bindings/serial/st,stm32-uart.yaml        |  15 ++-
 drivers/iio/chemical/ccs811.c                 | 112 ++++++++++++++++--
 2 files changed, 115 insertions(+), 12 deletions(-)

-- 
2.17.1

[PATCH v3 1/3] iio: chemical: Add support for external Reset and Wakeup in CCS811

[mani]

From: Manivannan Sadhasivam <mani@kernel.org>

CCS811 VOC sensor exposes nRESET and nWAKE pins which can be connected
to GPIO pins of the host controller. These pins can be used to externally
release the device from reset and also to wake it up before any I2C
transaction. The initial driver support assumed that the nRESET pin is not
connected and the nWAKE pin is tied to ground.

This commit improves it by adding support for controlling those two pins
externally using a host controller. For the case of reset, if the hardware
reset is not available, the mechanism to do software reset is also added.

As a side effect of doing this, the IIO device allocation needs to be
slightly moved to top of probe to make use of priv data early.

Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
---
 drivers/iio/chemical/ccs811.c | 105 ++++++++++++++++++++++++++++++----
 1 file changed, 94 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c
index 2ebdfc35bcda..1500e4b0dfbd 100644
--- a/drivers/iio/chemical/ccs811.c
+++ b/drivers/iio/chemical/ccs811.c
@@ -16,6 +16,7 @@
  */
 
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/buffer.h>
@@ -36,6 +37,7 @@
 #define CCS811_ERR		0xE0
 /* Used to transition from boot to application mode */
 #define CCS811_APP_START	0xF4
+#define CCS811_SW_RESET		0xFF
 
 /* Status register flags */
 #define CCS811_STATUS_ERROR		BIT(0)
@@ -74,6 +76,7 @@ struct ccs811_data {
 	struct mutex lock; /* Protect readings */
 	struct ccs811_reading buffer;
 	struct iio_trigger *drdy_trig;
+	struct gpio_desc *wakeup_gpio;
 	bool drdy_trig_on;
 };
 
@@ -166,10 +169,25 @@ static int ccs811_setup(struct i2c_client *client)
 					 CCS811_MODE_IAQ_1SEC);
 }
 
+static void ccs811_set_wakeup(struct ccs811_data *data, bool enable)
+{
+	if (!data->wakeup_gpio)
+		return;
+
+	gpiod_set_value(data->wakeup_gpio, enable);
+
+	if (enable)
+		usleep_range(50, 60);
+	else
+		usleep_range(20, 30);
+}
+
 static int ccs811_get_measurement(struct ccs811_data *data)
 {
 	int ret, tries = 11;
 
+	ccs811_set_wakeup(data, true);
+
 	/* Maximum waiting time: 1s, as measurements are made every second */
 	while (tries-- > 0) {
 		ret = i2c_smbus_read_byte_data(data->client, CCS811_STATUS);
@@ -183,9 +201,12 @@ static int ccs811_get_measurement(struct ccs811_data *data)
 	if (!(ret & CCS811_STATUS_DATA_READY))
 		return -EIO;
 
-	return i2c_smbus_read_i2c_block_data(data->client,
+	ret = i2c_smbus_read_i2c_block_data(data->client,
 					    CCS811_ALG_RESULT_DATA, 8,
 					    (char *)&data->buffer);
+	ccs811_set_wakeup(data, false);
+
+	return ret;
 }
 
 static int ccs811_read_raw(struct iio_dev *indio_dev,
@@ -336,6 +357,45 @@ static irqreturn_t ccs811_data_rdy_trigger_poll(int irq, void *private)
 	return IRQ_HANDLED;
 }
 
+static int ccs811_reset(struct i2c_client *client)
+{
+	struct gpio_desc *reset_gpio;
+	int ret;
+
+	reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
+					     GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio))
+		return PTR_ERR(reset_gpio);
+
+	/* Try to reset using nRESET pin if available else do SW reset */
+	if (reset_gpio) {
+		gpiod_set_value(reset_gpio, 1);
+		usleep_range(20, 30);
+		gpiod_set_value(reset_gpio, 0);
+	} else {
+		/*
+		 * As per the datasheet, this sequence of values needs to be
+		 * written to the SW_RESET register for triggering the soft
+		 * reset in the device and placing it in boot mode.
+		 */
+		static const u8 reset_seq[] = {
+			0x11, 0xE5, 0x72, 0x8A,
+		};
+
+		ret = i2c_smbus_write_i2c_block_data(client, CCS811_SW_RESET,
+					     sizeof(reset_seq), reset_seq);
+		if (ret < 0) {
+			dev_err(&client->dev, "Failed to reset sensor\n");
+			return ret;
+		}
+	}
+
+	/* tSTART delay required after reset */
+	usleep_range(1000, 2000);
+
+	return 0;
+}
+
 static int ccs811_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
@@ -348,36 +408,59 @@ static int ccs811_probe(struct i2c_client *client,
 				     | I2C_FUNC_SMBUS_READ_I2C_BLOCK))
 		return -EOPNOTSUPP;
 
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+
+	data->wakeup_gpio = devm_gpiod_get_optional(&client->dev, "wakeup",
+						    GPIOD_OUT_HIGH);
+	if (IS_ERR(data->wakeup_gpio))
+		return PTR_ERR(data->wakeup_gpio);
+
+	ccs811_set_wakeup(data, true);
+
+	ret = ccs811_reset(client);
+	if (ret) {
+		ccs811_set_wakeup(data, false);
+		return ret;
+	}
+
 	/* Check hardware id (should be 0x81 for this family of devices) */
 	ret = i2c_smbus_read_byte_data(client, CCS811_HW_ID);
-	if (ret < 0)
+	if (ret < 0) {
+		ccs811_set_wakeup(data, false);
 		return ret;
+	}
 
 	if (ret != CCS811_HW_ID_VALUE) {
 		dev_err(&client->dev, "hardware id doesn't match CCS81x\n");
+		ccs811_set_wakeup(data, false);
 		return -ENODEV;
 	}
 
 	ret = i2c_smbus_read_byte_data(client, CCS811_HW_VERSION);
-	if (ret < 0)
+	if (ret < 0) {
+		ccs811_set_wakeup(data, false);
 		return ret;
+	}
 
 	if ((ret & CCS811_HW_VERSION_MASK) != CCS811_HW_VERSION_VALUE) {
 		dev_err(&client->dev, "no CCS811 sensor\n");
+		ccs811_set_wakeup(data, false);
 		return -ENODEV;
 	}
 
-	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
-	if (!indio_dev)
-		return -ENOMEM;
-
 	ret = ccs811_setup(client);
-	if (ret < 0)
+	if (ret < 0) {
+		ccs811_set_wakeup(data, false);
 		return ret;
+	}
 
-	data = iio_priv(indio_dev);
-	i2c_set_clientdata(client, indio_dev);
-	data->client = client;
+	ccs811_set_wakeup(data, false);
 
 	mutex_init(&data->lock);
 
-- 
2.17.1

[PATCH v3 2/3] iio: chemical: Add OF match table for CCS811 VOC sensor

[mani]

From: Manivannan Sadhasivam <mani@kernel.org>

Add devicetree OF match table support for CCS811 VOC sensor.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
---
 drivers/iio/chemical/ccs811.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c
index 1500e4b0dfbd..3ecd633f9ed3 100644
--- a/drivers/iio/chemical/ccs811.c
+++ b/drivers/iio/chemical/ccs811.c
@@ -549,9 +549,16 @@ static const struct i2c_device_id ccs811_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, ccs811_id);
 
+static const struct of_device_id ccs811_dt_ids[] = {
+	{ .compatible = "ams,ccs811" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ccs811_dt_ids);
+
 static struct i2c_driver ccs811_driver = {
 	.driver = {
 		.name = "ccs811",
+		.of_match_table = ccs811_dt_ids,
 	},
 	.probe = ccs811_probe,
 	.remove = ccs811_remove,
-- 
2.17.1

[PATCH v3 3/3] dt-bindings: serial: Add binding for software flow control in STM32 UART

[mani]

From: Manivannan Sadhasivam <mani@kernel.org>

Add devicetree binding for software flow control in STM32 UART
controller. While at it, let's also fix one schema error reported by
`make dtbs_check`.

Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
---
 .../devicetree/bindings/serial/st,stm32-uart.yaml | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/serial/st,stm32-uart.yaml b/Documentation/devicetree/bindings/serial/st,stm32-uart.yaml
index 238c44192d31..ea5797a1b403 100644
--- a/Documentation/devicetree/bindings/serial/st,stm32-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/st,stm32-uart.yaml
@@ -38,13 +38,26 @@ properties:
     description: enable hardware flow control
     $ref: /schemas/types.yaml#/definitions/flag
 
+  st,sw-flow-ctrl:
+    description: enable software flow control
+    $ref: /schemas/types.yaml#/definitions/flag
+
+  rts-gpios:
+    description: RTS pin used if st,sw-flow-ctrl is true
+    maxItems: 1
+
+  cts-gpios:
+    description: CTS pin used if st,sw-flow-ctrl is true
+    maxItems: 1
+
   dmas:
     minItems: 1
     maxItems: 2
 
   dma-names:
     items:
-      enum: [ rx, tx ]
+      - const: rx
+      - const: tx
     minItems: 1
     maxItems: 2
 
-- 
2.17.1

Re: [PATCH v3 0/3] Add Reset and Wakeup support for CCS811

[Manivannan Sadhasivam]

On Wed, Apr 15, 2020 at 12:11:44AM +0530, mani@kernel.org wrote:
> From: Manivannan Sadhasivam <mani@kernel.org>
> 
> Hello,
> 
> This patchset adds external reset and wakeup support for CCS811 VOC
> gas sensor. The nRESET and nWAKE pins available on the device are
> utilised to provide these functionalities.
> 
> The patchset has been validated using CCS811 connected to STM32MP1 based
> board over I2C.
> 
> While at it, the devicetree yaml binding and OF match table for this sensor
> are also added.
> 
> Thanks,
> Mani
> 
> Changes in v3:
> 
> * Added ccs811_set_wake(false) to all error paths before calling it actually
> * Added Andy's reviewed-by tag
> * Added comment for reset procedure and dropped error print for gpio request
> 
> Changes in v2:
> 
> * Fixed DT binding schema and switched to dual license (GPL/BSD)
> * Returned actual error code from devm_gpiod_get_optional()
> * Dropped of.h include and of_match_ptr()
> 
> Manivannan Sadhasivam (3):
>   iio: chemical: Add support for external Reset and Wakeup in CCS811
>   iio: chemical: Add OF match table for CCS811 VOC sensor
>   dt-bindings: serial: Add binding for software flow control in STM32

Err... please ignore this series. I'll resend it.

Thanks,
Mani

>     UART
> 
>  .../bindings/serial/st,stm32-uart.yaml        |  15 ++-
>  drivers/iio/chemical/ccs811.c                 | 112 ++++++++++++++++--
>  2 files changed, 115 insertions(+), 12 deletions(-)
> 
> -- 
> 2.17.1
>