Commit a852162e authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (spd5118) Detect and support 16-bit register addressing 



Add support for SPD5118 compatible chips with 16-bit addressing enabled
which are connected to I2C controllers.

Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent be82d39c

drivers/hwmon/spd5118.c

+64 −11
Original line number Diff line number Diff line
@@ -461,7 +461,7 @@ static const struct regmap_range_cfg spd5118_i2c_regmap_range_cfg[] = { 
	},

};



static const struct regmap_config spd5118_i2c_regmap_config = {

static const struct regmap_config spd5118_regmap8_config = {

	.reg_bits = 8,

	.val_bits = 8,

	.max_register = 0x7ff,
@@ -473,6 +473,15 @@ static const struct regmap_config spd5118_i2c_regmap_config = { 
	.num_ranges = ARRAY_SIZE(spd5118_i2c_regmap_range_cfg),

};



static const struct regmap_config spd5118_regmap16_config = {

	.reg_bits = 16,

	.val_bits = 8,

	.max_register = 0x7ff,

	.writeable_reg = spd5118_writeable_reg,

	.volatile_reg = spd5118_volatile_reg,

	.cache_type = REGCACHE_MAPLE,

};



static int spd5118_suspend(struct device *dev)

{

	struct spd5118_data *data = dev_get_drvdata(dev);
@@ -510,7 +519,8 @@ static int spd5118_resume(struct device *dev) 


static DEFINE_SIMPLE_DEV_PM_OPS(spd5118_pm_ops, spd5118_suspend, spd5118_resume);



static int spd5118_common_probe(struct device *dev, struct regmap *regmap)

static int spd5118_common_probe(struct device *dev, struct regmap *regmap,

				bool is_16bit)

{

	unsigned int capability, revision, vendor, bank;

	struct spd5118_data *data;
@@ -527,12 +537,7 @@ static int spd5118_common_probe(struct device *dev, struct regmap *regmap) 
	if (!(capability & SPD5118_CAP_TS_SUPPORT))

		return -ENODEV;



	/*

	 * 16-bit register addresses are not (yet) supported with I2C.

	 * Therefore, if this is an I2C device, register addresses must be

	 * 8 bit wide.

	 */

	data->is_16bit = !!i2c_verify_adapter(dev);

	data->is_16bit = is_16bit;



	err = regmap_read(regmap, SPD5118_REG_REVISION, &revision);

	if (err)
@@ -675,21 +680,69 @@ static int spd5118_i2c_init(struct i2c_client *client) 
	return 0;

}



/*

 * 16-bit addressing note:

 *

 * If I2C_FUNC_I2C is not supported by an I2C adapter driver, regmap uses

 * SMBus operations as alternative. To simulate a read operation with a 16-bit

 * address, it writes the address using i2c_smbus_write_byte_data(), followed

 * by one or more calls to i2c_smbus_read_byte() to read the data.

 * Per spd5118 standard, a read operation after writing the address must start

 * with <Sr> (Repeat Start). However, a SMBus read byte operation starts with

 * <S> (Start). This resets the register address in the spd5118 chip. As result,

 * i2c_smbus_read_byte() always returns data from register address 0x00.

 *

 * A working alternative to access chips with 16-bit register addresses in the

 * absence of I2C_FUNC_I2C support is not known.

 *

 * For this reason, 16-bit addressing can only be supported with I2C if the

 * adapter supports I2C_FUNC_I2C.

 *

 * For I2C, the addressing mode selected by the BIOS must not be changed.

 * Experiments show that at least some PC BIOS versions will not change the

 * addressing mode on a soft reboot and end up in setup, claiming that some

 * configuration change happened. This will happen again after a power cycle,

 * which does reset the addressing mode. To prevent this from happening,

 * detect if 16-bit addressing is enabled and always use the currently

 * configured addressing mode.

 */



static int spd5118_i2c_probe(struct i2c_client *client)

{

	const struct regmap_config *config;

	struct device *dev = &client->dev;

	struct regmap *regmap;

	int err;

	int err, mode;

	bool is_16bit;



	err = spd5118_i2c_init(client);

	if (err)

		return err;



	regmap = devm_regmap_init_i2c(client, &spd5118_i2c_regmap_config);

	mode = i2c_smbus_read_byte_data(client, SPD5118_REG_I2C_LEGACY_MODE);

	if (mode < 0)

		return mode;



	is_16bit = mode & SPD5118_LEGACY_MODE_ADDR;

	if (is_16bit) {

		/*

		 * See 16-bit addressing note above explaining why it is

		 * necessary to check for I2C_FUNC_I2C support here.

		 */

		if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {

			dev_err(dev, "Adapter does not support 16-bit register addresses\n");

			return -ENODEV;

		}

		config = &spd5118_regmap16_config;

	} else {

		config = &spd5118_regmap8_config;

	}



	regmap = devm_regmap_init_i2c(client, config);

	if (IS_ERR(regmap))

		return dev_err_probe(dev, PTR_ERR(regmap), "regmap init failed\n");



	return spd5118_common_probe(dev, regmap);

	return spd5118_common_probe(dev, regmap, is_16bit);

}



static const struct i2c_device_id spd5118_i2c_id[] = {