iio: proximity: lidar: optimize i2c transactions

Optimize device tranactions using i2c transfers versus multiple
possibly racey i2c_smbus_* function calls, and only one transaction
for distance measurement. Falls back to smbus method if i2c
functionality isn't available.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 70 insertions, 25 deletions

diff --git a/drivers/iio/proximity/pulsedlight-lidar-lite-v2.c b/drivers/iio/proximity/pulsedlight-lidar-lite-v2.c
index be8ccef735f8..e7ea44d61942 100644
--- a/drivers/iio/proximity/pulsedlight-lidar-lite-v2.c
+++ b/drivers/iio/proximity/pulsedlight-lidar-lite-v2.c
@@ -36,8 +36,10 @@
 #define LIDAR_REG_STATUS_INVALID        BIT(3)
 #define LIDAR_REG_STATUS_READY          BIT(0)
 
-#define LIDAR_REG_DATA_HBYTE    0x0f
-#define LIDAR_REG_DATA_LBYTE    0x10
+#define LIDAR_REG_DATA_HBYTE            0x0f
+#define LIDAR_REG_DATA_LBYTE            0x10
+#define LIDAR_REG_DATA_WORD_READ        BIT(7)
+
 #define LIDAR_REG_PWR_CONTROL   0x65
 
 #define LIDAR_DRV_NAME "lidar"
@@ -46,6 +48,9 @@ struct lidar_data {
         struct iio_dev *indio_dev;
         struct i2c_client *client;
 
+        int (*xfer)(struct lidar_data *data, u8 reg, u8 *val, int len);
+        int i2c_enabled;
+
         u16 buffer[8]; /* 2 byte distance + 8 byte timestamp */
 };
 
@@ -64,7 +69,28 @@ static const struct iio_chan_spec lidar_channels[] = {
         IIO_CHAN_SOFT_TIMESTAMP(1),
 };
 
-static int lidar_read_byte(struct lidar_data *data, int reg)
+static int lidar_i2c_xfer(struct lidar_data *data, u8 reg, u8 *val, int len)
+{
+        struct i2c_client *client = data->client;
+        struct i2c_msg msg[2];
+        int ret;
+
+        msg[0].addr = client->addr;
+        msg[0].flags = client->flags | I2C_M_STOP;
+        msg[0].len = 1;
+        msg[0].buf  = (char *) ®
+
+        msg[1].addr = client->addr;
+        msg[1].flags = client->flags | I2C_M_RD;
+        msg[1].len = len;
+        msg[1].buf = (char *) val;
+
+        ret = i2c_transfer(client->adapter, msg, 2);
+
+        return (ret == 2) ? 0 : ret;
+}
+
+static int lidar_smbus_xfer(struct lidar_data *data, u8 reg, u8 *val, int len)
 {
         struct i2c_client *client = data->client;
         int ret;
@@ -74,17 +100,35 @@ static int lidar_read_byte(struct lidar_data *data, int reg)
          * so in turn i2c_smbus_read_byte_data cannot be used
          */
 
-        ret = i2c_smbus_write_byte(client, reg);
-        if (ret < 0) {
-                dev_err(&client->dev, "cannot write addr value");
-                return ret;
+        while (len--) {
+                ret = i2c_smbus_write_byte(client, reg++);
+                if (ret < 0) {
+                        dev_err(&client->dev, "cannot write addr value");
+                        return ret;
+                }
+
+                ret = i2c_smbus_read_byte(client);
+                if (ret < 0) {
+                        dev_err(&client->dev, "cannot read data value");
+                        return ret;
+                }
+
+                *(val++) = ret;
         }
 
-        ret = i2c_smbus_read_byte(client);
+        return 0;
+}
+
+static int lidar_read_byte(struct lidar_data *data, u8 reg)
+{
+        int ret;
+        u8 val;
+
+        ret = data->xfer(data, reg, &val, 1);
         if (ret < 0)
-                dev_err(&client->dev, "cannot read data value");
+                return ret;
 
-        return ret;
+        return val;
 }
 
 static inline int lidar_write_control(struct lidar_data *data, int val)
@@ -100,22 +144,14 @@ static inline int lidar_write_power(struct lidar_data *data, int val)
 
 static int lidar_read_measurement(struct lidar_data *data, u16 *reg)
 {
-        int ret;
-        int val;
-
-        ret = lidar_read_byte(data, LIDAR_REG_DATA_HBYTE);
-        if (ret < 0)
-                return ret;
-        val = ret << 8;
+        int ret = data->xfer(data, LIDAR_REG_DATA_HBYTE |
+                        (data->i2c_enabled ? LIDAR_REG_DATA_WORD_READ : 0),
+                        (u8 *) reg, 2);
 
-        ret = lidar_read_byte(data, LIDAR_REG_DATA_LBYTE);
-        if (ret < 0)
-                return ret;
+        if (!ret)
+                *reg = be16_to_cpu(*reg);
 
-        val |= ret;
-        *reg = val;
-
-        return 0;
+        return ret;
 }
 
 static int lidar_get_measurement(struct lidar_data *data, u16 *reg)
@@ -233,6 +269,16 @@ static int lidar_probe(struct i2c_client *client,
         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
         if (!indio_dev)
                 return -ENOMEM;
+        data = iio_priv(indio_dev);
+
+        if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+                data->xfer = lidar_i2c_xfer;
+                data->i2c_enabled = 1;
+        } else if (i2c_check_functionality(client->adapter,
+                                I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
+                data->xfer = lidar_smbus_xfer;
+        else
+                return -ENOTSUPP;
 
         indio_dev->info = &lidar_info;
         indio_dev->name = LIDAR_DRV_NAME;
@@ -240,7 +286,6 @@ static int lidar_probe(struct i2c_client *client,
         indio_dev->num_channels = ARRAY_SIZE(lidar_channels);
         indio_dev->modes = INDIO_DIRECT_MODE;
 
-        data = iio_priv(indio_dev);
         i2c_set_clientdata(client, indio_dev);
 
         data->client = client;