Unverified Commit 82f25bd7 authored by AceLan Kao's avatar AceLan Kao Committed by Mark Brown
Browse files

regmap-i2c: add 16-bit width registers support 

This allows to access data with 16-bit width of registers
via i2c SMBus block functions.

The multi-command sequence of the reading function is not safe
and may read the wrong data from other address if other commands
are sent in-between the SMBus commands in the read function.

Read performance:
   32768 bytes (33 kB, 32 KiB) copied, 11.4869 s, 2.9 kB/s
Write performance(with 1-byte page):
   32768 bytes (33 kB, 32 KiB) copied, 129.591 s, 0.3 kB/s

The implementation is inspired by below commit
https://patchwork.ozlabs.org/patch/545292/



v2: add more descriptions about the issue that maybe introduced
    by this commit

Signed-off-by: default avatarAceLan Kao <acelan.kao@canonical.com>
Link: https://lore.kernel.org/r/20200424123358.144850-1-acelan.kao@canonical.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 148c01d1

drivers/base/regmap/regmap-i2c.c

+61 −0
Original line number Diff line number Diff line
@@ -246,6 +246,63 @@ static const struct regmap_bus regmap_i2c_smbus_i2c_block = { 
	.max_raw_write = I2C_SMBUS_BLOCK_MAX,

};



static int regmap_i2c_smbus_i2c_write_reg16(void *context, const void *data,

				      size_t count)

{

	struct device *dev = context;

	struct i2c_client *i2c = to_i2c_client(dev);



	if (count < 2)

		return -EINVAL;



	count--;

	return i2c_smbus_write_i2c_block_data(i2c, ((u8 *)data)[0], count,

					      (u8 *)data + 1);

}



static int regmap_i2c_smbus_i2c_read_reg16(void *context, const void *reg,

				     size_t reg_size, void *val,

				     size_t val_size)

{

	struct device *dev = context;

	struct i2c_client *i2c = to_i2c_client(dev);

	int ret, count, len = val_size;



	if (reg_size != 2)

		return -EINVAL;



	ret = i2c_smbus_write_byte_data(i2c, ((u16 *)reg)[0] & 0xff,

					((u16 *)reg)[0] >> 8);

	if (ret < 0)

		return ret;



	count = 0;

	do {

		/* Current Address Read */

		ret = i2c_smbus_read_byte(i2c);

		if (ret < 0)

			break;



		*((u8 *)val++) = ret;

		count++;

		len--;

	} while (len > 0);



	if (count == val_size)

		return 0;

	else if (ret < 0)

		return ret;

	else

		return -EIO;

}



static const struct regmap_bus regmap_i2c_smbus_i2c_block_reg16 = {

	.write = regmap_i2c_smbus_i2c_write_reg16,

	.read = regmap_i2c_smbus_i2c_read_reg16,

	.max_raw_read = I2C_SMBUS_BLOCK_MAX,

	.max_raw_write = I2C_SMBUS_BLOCK_MAX,

};



static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,

					const struct regmap_config *config)

{
@@ -255,6 +312,10 @@ static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c, 
		 i2c_check_functionality(i2c->adapter,

					 I2C_FUNC_SMBUS_I2C_BLOCK))

		return &regmap_i2c_smbus_i2c_block;

	else if (config->val_bits == 8 && config->reg_bits == 16 &&

		i2c_check_functionality(i2c->adapter,

					I2C_FUNC_SMBUS_I2C_BLOCK))

		return &regmap_i2c_smbus_i2c_block_reg16;

	else if (config->val_bits == 16 && config->reg_bits == 8 &&

		 i2c_check_functionality(i2c->adapter,

					 I2C_FUNC_SMBUS_WORD_DATA))

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