[PATCH v2 0/2] bmg160 driver optimizations

[PATCH v2 0/2] bmg160 driver optimizations

[Irina Tirdea]

Adds optimization of i2c transactions in trigger handler and
usage of available_scan_masks for bmg160.

Changes in v2:
 - fallback to i2c word transactions if i2c block transactions are not supported
 - use available_scan_masks to let the iio core choose the values selected
by the user instead of doing the check in the driver's interrupt handler
 - check functionality for i2c byte and word read

Irina Tirdea (2):
  iio: gyro: bmg160: use available_scan_masks
  iio: gyro: bmg160: optimize i2c transfers in trigger handler

 drivers/iio/gyro/bmg160.c | 50 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 39 insertions(+), 11 deletions(-)

-- 
1.9.1

[PATCH v2 1/2] iio: gyro: bmg160: use available_scan_masks

[Irina Tirdea]

Use available_scan_masks to allow the iio core to select
the data to send to userspace depending on which axes are
enabled, instead of doing this in the driver's interrupt
handler.

This also fixes the issue of accessing the buffer scan_mask
instead of active_scan_mask, since these might not be the
same due to client devices.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/iio/gyro/bmg160.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/gyro/bmg160.c b/drivers/iio/gyro/bmg160.c
index 60451b3..6ccf333 100644
--- a/drivers/iio/gyro/bmg160.c
+++ b/drivers/iio/gyro/bmg160.c
@@ -115,6 +115,7 @@ enum bmg160_axis {
 	AXIS_X,
 	AXIS_Y,
 	AXIS_Z,
+	AXIS_MAX,
 };
 
 static const struct {
@@ -814,6 +815,8 @@ static const struct iio_info bmg160_info = {
 	.driver_module		= THIS_MODULE,
 };
 
+static const unsigned long bmg160_scan_masks[] = {0x7, 0};
+
 static irqreturn_t bmg160_trigger_handler(int irq, void *p)
 {
 	struct iio_poll_func *pf = p;
@@ -822,8 +825,7 @@ static irqreturn_t bmg160_trigger_handler(int irq, void *p)
 	int bit, ret, i = 0;
 
 	mutex_lock(&data->mutex);
-	for_each_set_bit(bit, indio_dev->buffer->scan_mask,
-			 indio_dev->masklength) {
+	for (bit = 0; bit < AXIS_MAX; bit++)
 		ret = i2c_smbus_read_word_data(data->client,
 					       BMG160_AXIS_TO_REG(bit));
 		if (ret < 0) {
@@ -1060,6 +1062,7 @@ static int bmg160_probe(struct i2c_client *client,
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->channels = bmg160_channels;
 	indio_dev->num_channels = ARRAY_SIZE(bmg160_channels);
+	indio_dev->available_scan_masks = bmg160_scan_masks;
 	indio_dev->name = name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &bmg160_info;
-- 
1.9.1

[PATCH v2 2/2] iio: gyro: bmg160: optimize i2c transfers in trigger handler

[Irina Tirdea]

Some i2c busses (e.g.: Synopsys DesignWare I2C adapter) need to
enable/disable the bus at each i2c transfer and must wait for
the enable/disable to happen before sending the data.

When reading data in the trigger handler, the bmg160 driver does
one i2c transfer for each axis. This has an impact on the frequency
of the gyroscope at high sample rates due to additional delays
introduced by the i2c bus at each transfer.

Reading all axis values in one i2c transfer reduces the delays
introduced by the i2c bus. In case i2c block read is not supported,
fallback to reading each axis as a separate word.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/iio/gyro/bmg160.c | 45 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/gyro/bmg160.c b/drivers/iio/gyro/bmg160.c
index 6ccf333..9720cd6 100644
--- a/drivers/iio/gyro/bmg160.c
+++ b/drivers/iio/gyro/bmg160.c
@@ -109,6 +109,8 @@ struct bmg160_data {
 	bool dready_trigger_on;
 	bool motion_trigger_on;
 	int64_t timestamp;
+	s32 (*read_block_data)(const struct i2c_client *client, u8 command,
+			       u8 length, u8 *values);
 };
 
 enum bmg160_axis {
@@ -136,6 +138,23 @@ static const struct {
 			   { 133, BMG160_RANGE_250DPS},
 			   { 66, BMG160_RANGE_125DPS} };
 
+static s32 bmg160_read_block_data(const struct i2c_client *client,
+				  u8 command, u8 length, u8 *values)
+{
+	s32 data;
+	u8 i;
+
+	for (i = 0; i < length; i += 2) {
+		data = i2c_smbus_read_word_data(client, command + i);
+		if (data < 0)
+			return data;
+
+		values[i] = data & 0xFF;
+		values[i+1] = data >> 8;
+	}
+	return i;
+}
+
 static int bmg160_set_mode(struct bmg160_data *data, u8 mode)
 {
 	int ret;
@@ -822,19 +841,14 @@ static irqreturn_t bmg160_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmg160_data *data = iio_priv(indio_dev);
-	int bit, ret, i = 0;
+	int ret;
 
 	mutex_lock(&data->mutex);
-	for (bit = 0; bit < AXIS_MAX; bit++)
-		ret = i2c_smbus_read_word_data(data->client,
-					       BMG160_AXIS_TO_REG(bit));
-		if (ret < 0) {
-			mutex_unlock(&data->mutex);
-			goto err;
-		}
-		data->buffer[i++] = ret;
-	}
+	ret = data->read_block_data(data->client, BMG160_REG_XOUT_L,
+				    AXIS_MAX * 2, (u8 *) data->buffer);
 	mutex_unlock(&data->mutex);
+	if (ret < 0)
+		goto err;
 
 	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
 					   data->timestamp);
@@ -1039,6 +1053,11 @@ static int bmg160_probe(struct i2c_client *client,
 	int ret;
 	const char *name = NULL;
 
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_BYTE_DATA |
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENODEV;
+
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;
@@ -1051,6 +1070,12 @@ static int bmg160_probe(struct i2c_client *client,
 	if (ret < 0)
 		return ret;
 
+	if (i2c_check_functionality(client->adapter,
+				    I2C_FUNC_SMBUS_READ_I2C_BLOCK))
+		data->read_block_data = i2c_smbus_read_i2c_block_data;
+	else
+		data->read_block_data = bmg160_read_block_data;
+
 	mutex_init(&data->mutex);
 
 	if (id)
-- 
1.9.1

Re: [PATCH v2 0/2] bmg160 driver optimizations

[Peter Meerwald]

> Adds optimization of i2c transactions in trigger handler and
> usage of available_scan_masks for bmg160.

same concerns as with bmc150 and kxcjk-1013
 
> Changes in v2:
>  - fallback to i2c word transactions if i2c block transactions are not supported
>  - use available_scan_masks to let the iio core choose the values selected
> by the user instead of doing the check in the driver's interrupt handler
>  - check functionality for i2c byte and word read
> 
> Irina Tirdea (2):
>   iio: gyro: bmg160: use available_scan_masks
>   iio: gyro: bmg160: optimize i2c transfers in trigger handler
> 
>  drivers/iio/gyro/bmg160.c | 50 ++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 39 insertions(+), 11 deletions(-)
> 
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)