iio: ak8975: add definition structure per compass type

For each type of compass supported (AK8975 and AK8963),
add a definition structure for register masks, important registers,
raw data interpretation.
This change will make integrating new type of devices easier.

Remove i2c register cache. It is only used for one single register.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/magnetometer/ak8975.c

@@ -86,13 +86,155 @@
 #define AK8975_MAX_CONVERSION_TIMEOUT	500
 #define AK8975_CONVERSION_DONE_POLL_TIME 10
 #define AK8975_DATA_READY_TIMEOUT	((100*HZ)/1000)
-#define RAW_TO_GAUSS_8975(asa) ((((asa) + 128) * 3000) / 256)
-#define RAW_TO_GAUSS_8963(asa) ((((asa) + 128) * 6000) / 256)
+
+/*
+ * Precalculate scale factor (in Gauss units) for each axis and
+ * store in the device data.
+ *
+ * This scale factor is axis-dependent, and is derived from 3 calibration
+ * factors ASA(x), ASA(y), and ASA(z).
+ *
+ * These ASA values are read from the sensor device at start of day, and
+ * cached in the device context struct.
+ *
+ * Adjusting the flux value with the sensitivity adjustment value should be
+ * done via the following formula:
+ *
+ * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
+ * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
+ * is the resultant adjusted value.
+ *
+ * We reduce the formula to:
+ *
+ * Hadj = H * (ASA + 128) / 256
+ *
+ * H is in the range of -4096 to 4095.  The magnetometer has a range of
+ * +-1229uT.  To go from the raw value to uT is:
+ *
+ * HuT = H * 1229/4096, or roughly, 3/10.
+ *
+ * Since 1uT = 0.01 gauss, our final scale factor becomes:
+ *
+ * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
+ * Hadj = H * ((ASA + 128) * 0.003) / 256
+ *
+ * Since ASA doesn't change, we cache the resultant scale factor into the
+ * device context in ak8975_setup().
+ *
+ * Given we use IIO_VAL_INT_PLUS_MICRO bit when displaying the scale, we
+ * multiply the stored scale value by 1e6.
+ */
+static long ak8975_raw_to_gauss(u16 data)
+{
+	return (((long)data + 128) * 3000) / 256;
+}
+
+/*
+ * For AK8963, same calculation, but the device is less sensitive:
+ *
+ * H is in the range of +-8190.  The magnetometer has a range of
+ * +-4912uT.  To go from the raw value to uT is:
+ *
+ * HuT = H * 4912/8190, or roughly, 6/10, instead of 3/10.
+ */
+static long ak8963_raw_to_gauss(u16 data)
+{
+	return (((long)data + 128) * 6000) / 256;
+}
 
 /* Compatible Asahi Kasei Compass parts */
 enum asahi_compass_chipset {
 	AK8975,
 	AK8963,
+	AK_MAX_TYPE
+};
+
+enum ak_ctrl_reg_addr {
+	ST1,
+	ST2,
+	CNTL,
+	ASA_BASE,
+	MAX_REGS,
+	REGS_END,
+};
+
+enum ak_ctrl_reg_mask {
+	ST1_DRDY,
+	ST2_HOFL,
+	ST2_DERR,
+	CNTL_MODE,
+	MASK_END,
+};
+
+enum ak_ctrl_mode {
+	POWER_DOWN,
+	MODE_ONCE,
+	SELF_TEST,
+	FUSE_ROM,
+	MODE_END,
+};
+
+struct ak_def {
+	enum asahi_compass_chipset type;
+	long (*raw_to_gauss)(u16 data);
+	u16 range;
+	u8 ctrl_regs[REGS_END];
+	u8 ctrl_masks[MASK_END];
+	u8 ctrl_modes[MODE_END];
+	u8 data_regs[3];
+};
+
+static struct ak_def ak_def_array[AK_MAX_TYPE] = {
+	{
+		.type = AK8975,
+		.raw_to_gauss = ak8975_raw_to_gauss,
+		.range = 4096,
+		.ctrl_regs = {
+			AK8975_REG_ST1,
+			AK8975_REG_ST2,
+			AK8975_REG_CNTL,
+			AK8975_REG_ASAX,
+			AK8975_MAX_REGS},
+		.ctrl_masks = {
+			AK8975_REG_ST1_DRDY_MASK,
+			AK8975_REG_ST2_HOFL_MASK,
+			AK8975_REG_ST2_DERR_MASK,
+			AK8975_REG_CNTL_MODE_MASK},
+		.ctrl_modes = {
+			AK8975_REG_CNTL_MODE_POWER_DOWN,
+			AK8975_REG_CNTL_MODE_ONCE,
+			AK8975_REG_CNTL_MODE_SELF_TEST,
+			AK8975_REG_CNTL_MODE_FUSE_ROM},
+		.data_regs = {
+			AK8975_REG_HXL,
+			AK8975_REG_HYL,
+			AK8975_REG_HZL},
+	},
+	{
+		.type = AK8963,
+		.raw_to_gauss = ak8963_raw_to_gauss,
+		.range = 8190,
+		.ctrl_regs = {
+			AK8975_REG_ST1,
+			AK8975_REG_ST2,
+			AK8975_REG_CNTL,
+			AK8975_REG_ASAX,
+			AK8975_MAX_REGS},
+		.ctrl_masks = {
+			AK8975_REG_ST1_DRDY_MASK,
+			AK8975_REG_ST2_HOFL_MASK,
+			0,
+			AK8975_REG_CNTL_MODE_MASK},
+		.ctrl_modes = {
+			AK8975_REG_CNTL_MODE_POWER_DOWN,
+			AK8975_REG_CNTL_MODE_ONCE,
+			AK8975_REG_CNTL_MODE_SELF_TEST,
+			AK8975_REG_CNTL_MODE_FUSE_ROM},
+		.data_regs = {
+			AK8975_REG_HXL,
+			AK8975_REG_HYL,
+			AK8975_REG_HZL},
+	},
 };
 
 /*
@@ -100,40 +242,36 @@ enum asahi_compass_chipset {
  */
 struct ak8975_data {
 	struct i2c_client	*client;
+	struct ak_def		*def;
 	struct attribute_group	attrs;
 	struct mutex		lock;
 	u8			asa[3];
 	long			raw_to_gauss[3];
-	u8			reg_cache[AK8975_MAX_REGS];
 	int			eoc_gpio;
 	int			eoc_irq;
 	wait_queue_head_t	data_ready_queue;
 	unsigned long		flags;
-	enum asahi_compass_chipset chipset;
-};
-
-static const int ak8975_index_to_reg[] = {
-	AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
+	u8			cntl_cache;
 };
 
 /*
- * Helper function to write to the I2C device's registers.
+ * Helper function to write to CNTL register.
  */
-static int ak8975_write_data(struct i2c_client *client,
-			     u8 reg, u8 val, u8 mask, u8 shift)
+static int ak8975_set_mode(struct ak8975_data *data, enum ak_ctrl_mode mode)
 {
-	struct iio_dev *indio_dev = i2c_get_clientdata(client);
-	struct ak8975_data *data = iio_priv(indio_dev);
 	u8 regval;
 	int ret;
 
-	regval = (data->reg_cache[reg] & ~mask) | (val << shift);
-	ret = i2c_smbus_write_byte_data(client, reg, regval);
+	regval = (data->cntl_cache & ~data->def->ctrl_masks[CNTL_MODE]) |
+		 data->def->ctrl_modes[mode];
+	ret = i2c_smbus_write_byte_data(data->client,
+					data->def->ctrl_regs[CNTL], regval);
 	if (ret < 0) {
-		dev_err(&client->dev, "Write to device fails status %x\n", ret);
 		return ret;
 	}
-	data->reg_cache[reg] = regval;
+	data->cntl_cache = regval;
+	/* After mode change wait atleast 100us */
+	usleep_range(100, 500);
 
 	return 0;
 }
@@ -207,18 +345,15 @@ static int ak8975_setup(struct i2c_client *client)
 	}
 
 	/* Write the fused rom access mode. */
-	ret = ak8975_write_data(client,
-				AK8975_REG_CNTL,
-				AK8975_REG_CNTL_MODE_FUSE_ROM,
-				AK8975_REG_CNTL_MODE_MASK,
-				AK8975_REG_CNTL_MODE_SHIFT);
+	ret = ak8975_set_mode(data, FUSE_ROM);
 	if (ret < 0) {
 		dev_err(&client->dev, "Error in setting fuse access mode\n");
 		return ret;
 	}
 
 	/* Get asa data and store in the device data. */
-	ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
+	ret = i2c_smbus_read_i2c_block_data(client,
+					    data->def->ctrl_regs[ASA_BASE],
 					    3, data->asa);
 	if (ret < 0) {
 		dev_err(&client->dev, "Not able to read asa data\n");
@@ -226,11 +361,7 @@ static int ak8975_setup(struct i2c_client *client)
 	}
 
 	/* After reading fuse ROM data set power-down mode */
-	ret = ak8975_write_data(client,
-				AK8975_REG_CNTL,
-				AK8975_REG_CNTL_MODE_POWER_DOWN,
-				AK8975_REG_CNTL_MODE_MASK,
-				AK8975_REG_CNTL_MODE_SHIFT);
+	ret = ak8975_set_mode(data, POWER_DOWN);
 	if (ret < 0) {
 		dev_err(&client->dev, "Error in setting power-down mode\n");
 		return ret;
@@ -245,56 +376,9 @@ static int ak8975_setup(struct i2c_client *client)
 		}
 	}
 
-/*
- * Precalculate scale factor (in Gauss units) for each axis and
- * store in the device data.
- *
- * This scale factor is axis-dependent, and is derived from 3 calibration
- * factors ASA(x), ASA(y), and ASA(z).
- *
- * These ASA values are read from the sensor device at start of day, and
- * cached in the device context struct.
- *
- * Adjusting the flux value with the sensitivity adjustment value should be
- * done via the following formula:
- *
- * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
- *
- * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
- * is the resultant adjusted value.
- *
- * We reduce the formula to:
- *
- * Hadj = H * (ASA + 128) / 256
- *
- * H is in the range of -4096 to 4095.  The magnetometer has a range of
- * +-1229uT.  To go from the raw value to uT is:
- *
- * HuT = H * 1229/4096, or roughly, 3/10.
- *
- * Since 1uT = 0.01 gauss, our final scale factor becomes:
- *
- * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
- * Hadj = H * ((ASA + 128) * 0.003) / 256
- *
- * Since ASA doesn't change, we cache the resultant scale factor into the
- * device context in ak8975_setup().
- */
-	if (data->chipset == AK8963) {
-		/*
-		 * H range is +-8190 and magnetometer range is +-4912.
-		 * So HuT using the above explanation for 8975,
-		 * 4912/8190 = ~ 6/10.
-		 * So the Hadj should use 6/10 instead of 3/10.
-		 */
-		data->raw_to_gauss[0] = RAW_TO_GAUSS_8963(data->asa[0]);
-		data->raw_to_gauss[1] = RAW_TO_GAUSS_8963(data->asa[1]);
-		data->raw_to_gauss[2] = RAW_TO_GAUSS_8963(data->asa[2]);
-	} else {
-		data->raw_to_gauss[0] = RAW_TO_GAUSS_8975(data->asa[0]);
-		data->raw_to_gauss[1] = RAW_TO_GAUSS_8975(data->asa[1]);
-		data->raw_to_gauss[2] = RAW_TO_GAUSS_8975(data->asa[2]);
-	}
+	data->raw_to_gauss[0] = data->def->raw_to_gauss(data->asa[0]);
+	data->raw_to_gauss[1] = data->def->raw_to_gauss(data->asa[1]);
+	data->raw_to_gauss[2] = data->def->raw_to_gauss(data->asa[2]);
 
 	return 0;
 }
@@ -317,7 +401,7 @@ static int wait_conversion_complete_gpio(struct ak8975_data *data)
 		return -EINVAL;
 	}
 
-	ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
+	ret = i2c_smbus_read_byte_data(client, data->def->ctrl_regs[ST1]);
 	if (ret < 0)
 		dev_err(&client->dev, "Error in reading ST1\n");
 
@@ -334,7 +418,8 @@ static int wait_conversion_complete_polled(struct ak8975_data *data)
 	/* Wait for the conversion to complete. */
 	while (timeout_ms) {
 		msleep(AK8975_CONVERSION_DONE_POLL_TIME);
-		ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
+		ret = i2c_smbus_read_byte_data(client,
+					       data->def->ctrl_regs[ST1]);
 		if (ret < 0) {
 			dev_err(&client->dev, "Error in reading ST1\n");
 			return ret;
@@ -377,11 +462,7 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 	mutex_lock(&data->lock);
 
 	/* Set up the device for taking a sample. */
-	ret = ak8975_write_data(client,
-				AK8975_REG_CNTL,
-				AK8975_REG_CNTL_MODE_ONCE,
-				AK8975_REG_CNTL_MODE_MASK,
-				AK8975_REG_CNTL_MODE_SHIFT);
+	ret = ak8975_set_mode(data, MODE_ONCE);
 	if (ret < 0) {
 		dev_err(&client->dev, "Error in setting operating mode\n");
 		goto exit;
@@ -398,14 +479,15 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 		goto exit;
 
 	/* This will be executed only for non-interrupt based waiting case */
-	if (ret & AK8975_REG_ST1_DRDY_MASK) {
-		ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
+	if (ret & data->def->ctrl_masks[ST1_DRDY]) {
+		ret = i2c_smbus_read_byte_data(client,
+					       data->def->ctrl_regs[ST2]);
 		if (ret < 0) {
 			dev_err(&client->dev, "Error in reading ST2\n");
 			goto exit;
 		}
-		if (ret & (AK8975_REG_ST2_DERR_MASK |
-			   AK8975_REG_ST2_HOFL_MASK)) {
+		if (ret & (data->def->ctrl_masks[ST2_DERR] |
+			   data->def->ctrl_masks[ST2_HOFL])) {
 			dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
 			ret = -EINVAL;
 			goto exit;
@@ -414,7 +496,7 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 
 	/* Read the flux value from the appropriate register
 	   (the register is specified in the iio device attributes). */
-	ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
+	ret = i2c_smbus_read_word_data(client, data->def->data_regs[index]);
 	if (ret < 0) {
 		dev_err(&client->dev, "Read axis data fails\n");
 		goto exit;
@@ -423,7 +505,7 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 	mutex_unlock(&data->lock);
 
 	/* Clamp to valid range. */
-	*val = clamp_t(s16, ret, -4096, 4095);
+	*val = clamp_t(s16, ret, -data->def->range, data->def->range);
 	return IIO_VAL_INT;
 
 exit:
@@ -497,6 +579,7 @@ static int ak8975_probe(struct i2c_client *client,
 	int eoc_gpio;
 	int err;
 	const char *name = NULL;
+	enum asahi_compass_chipset chipset;
 
 	/* Grab and set up the supplied GPIO. */
 	if (client->dev.platform_data)
@@ -536,14 +619,20 @@ static int ak8975_probe(struct i2c_client *client,
 
 	/* id will be NULL when enumerated via ACPI */
 	if (id) {
-		data->chipset =
-			(enum asahi_compass_chipset)(id->driver_data);
+		chipset = (enum asahi_compass_chipset)(id->driver_data);
 		name = id->name;
 	} else if (ACPI_HANDLE(&client->dev))
-		name = ak8975_match_acpi_device(&client->dev, &data->chipset);
+		name = ak8975_match_acpi_device(&client->dev, &chipset);
 	else
 		return -ENOSYS;
 
+	if (chipset >= AK_MAX_TYPE) {
+		dev_err(&client->dev, "AKM device type unsupported: %d\n",
+			chipset);
+		return -ENODEV;
+	}
+
+	data->def = &ak_def_array[chipset];
 	dev_dbg(&client->dev, "Asahi compass chip %s\n", name);
 
 	/* Perform some basic start-of-day setup of the device. */
@@ -574,7 +663,9 @@ MODULE_DEVICE_TABLE(i2c, ak8975_id);
 static const struct of_device_id ak8975_of_match[] = {
 	{ .compatible = "asahi-kasei,ak8975", },
 	{ .compatible = "ak8975", },
-	{ }
+	{ .compatible = "asahi-kasei,ak8963", },
+	{ .compatible = "ak8963", },
+	{}
 };
 MODULE_DEVICE_TABLE(of, ak8975_of_match);