[PATCH 1/1][SRU][Focal] UBUNTU: SAUCE: regmap-i2c: add 16-bit width registers support

[Stefan Bader]

On 04.05.20 13:15, AceLan Kao wrote:
> BugLink: https://bugs.launchpad.net/bugs/1876699
> 
> 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: AceLan Kao <acelan.kao at canonical.com>
> ---

Somehow neither the commit message nor the justification in the bug report are
explaining what benefit (what is fixed) of this change is. Why would we want to
pick this up?

If there is a better reason, this is now at least in linux-next:

commit 82f25bd73c0bee4d29df47007a4f7290695b7db7

so it could be a proper cherry-pick.

-Stefan
>  drivers/base/regmap/regmap-i2c.c | 61 ++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c
> index ac9b31c57967..7f924797be58 100644
> --- a/drivers/base/regmap/regmap-i2c.c
> +++ b/drivers/base/regmap/regmap-i2c.c
> @@ -246,6 +246,63 @@ static 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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