[1/2] usb: typec: tps6598x: handle block reads separately with plain-I2C adapters

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Apr 18, 2018 at 03:34:09PM +0300, Heikki Krogerus wrote:
> If the I2C adapter that the PD controller is attached to
> does not support SMBus protocol, the driver needs to handle
> block reads separately. The first byte returned in block
> read protocol will show the total number of bytes. It needs
> to be stripped away.
> 
> This is handled separately in the driver only because right
> now we have no way of requesting the used protocol with
> regmap-i2c. This is in practice a workaround for what is
> really a problem in regmap-i2c. The other option would have
> been to register custom regmap, or not use regmap at all,
> however, since the solution is very simple, I choose to use
> it in this case for convenience. It is easy to remove once
> we figure out how to handle this kind of cases in
> regmap-i2c.
> 
> Fixes: 0a4c005bd171 ("usb: typec: driver for TI TPS6598x USB Power Delivery controllers")
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
>  drivers/usb/typec/tps6598x.c | 42 ++++++++++++++++++++++++++++++------
>  1 file changed, 35 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/typec/tps6598x.c b/drivers/usb/typec/tps6598x.c
> index 8b8406867c02..82f09cd9792d 100644
> --- a/drivers/usb/typec/tps6598x.c
> +++ b/drivers/usb/typec/tps6598x.c
> @@ -73,6 +73,7 @@ struct tps6598x {
>  	struct device *dev;
>  	struct regmap *regmap;
>  	struct mutex lock; /* device lock */
> +	u8 i2c_protocol:1;
>  
>  	struct typec_port *port;
>  	struct typec_partner *partner;
> @@ -80,6 +81,23 @@ struct tps6598x {
>  	struct typec_capability typec_cap;
>  };
>  
> +static int
> +tps6598x_block_read(struct tps6598x *tps, u8 reg, void *val, ssize_t len)
> +{
> +	u8 data[len + 1];
> +	int ret;
> +
> +	if (!tps->i2c_protocol)
> +		return regmap_raw_read(tps->regmap, reg, val, len);
> +
> +	ret = regmap_raw_read(tps->regmap, reg, data, sizeof(data));
> +	if (ret)
> +		return ret;
> +

Sanity check ?
	if (data[0] != len)
		return -Esomething;

Other than that,

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> +	memcpy(val, &data[1], len);
> +	return 0;
> +}
> +
>  static inline int tps6598x_read16(struct tps6598x *tps, u8 reg, u16 *val)
>  {
>  	return regmap_raw_read(tps->regmap, reg, val, sizeof(u16));
> @@ -87,12 +105,12 @@ static inline int tps6598x_read16(struct tps6598x *tps, u8 reg, u16 *val)
>  
>  static inline int tps6598x_read32(struct tps6598x *tps, u8 reg, u32 *val)
>  {
> -	return regmap_raw_read(tps->regmap, reg, val, sizeof(u32));
> +	return tps6598x_block_read(tps, reg, val, sizeof(u32));
>  }
>  
>  static inline int tps6598x_read64(struct tps6598x *tps, u8 reg, u64 *val)
>  {
> -	return regmap_raw_read(tps->regmap, reg, val, sizeof(u64));
> +	return tps6598x_block_read(tps, reg, val, sizeof(u64));
>  }
>  
>  static inline int tps6598x_write16(struct tps6598x *tps, u8 reg, u16 val)
> @@ -121,8 +139,8 @@ static int tps6598x_read_partner_identity(struct tps6598x *tps)
>  	struct tps6598x_rx_identity_reg id;
>  	int ret;
>  
> -	ret = regmap_raw_read(tps->regmap, TPS_REG_RX_IDENTITY_SOP,
> -			      &id, sizeof(id));
> +	ret = tps6598x_block_read(tps, TPS_REG_RX_IDENTITY_SOP,
> +				  &id, sizeof(id));
>  	if (ret)
>  		return ret;
>  
> @@ -224,13 +242,13 @@ static int tps6598x_exec_cmd(struct tps6598x *tps, const char *cmd,
>  	} while (val);
>  
>  	if (out_len) {
> -		ret = regmap_raw_read(tps->regmap, TPS_REG_DATA1,
> -				      out_data, out_len);
> +		ret = tps6598x_block_read(tps, TPS_REG_DATA1,
> +					  out_data, out_len);
>  		if (ret)
>  			return ret;
>  		val = out_data[0];
>  	} else {
> -		ret = regmap_read(tps->regmap, TPS_REG_DATA1, &val);
> +		ret = tps6598x_block_read(tps, TPS_REG_DATA1, &val, sizeof(u8));
>  		if (ret)
>  			return ret;
>  	}
> @@ -385,6 +403,16 @@ static int tps6598x_probe(struct i2c_client *client)
>  	if (!vid)
>  		return -ENODEV;
>  
> +	/*
> +	 * Checking can the adapter handle SMBus protocol. If if can not, the
> +	 * driver needs to take care of block reads separately.
> +	 *
> +	 * FIXME: Testing with I2C_FUNC_I2C. regmap-i2c uses I2C protocol
> +	 * unconditionally if the adapter has I2C_FUNC_I2C set.
> +	 */
> +	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> +		tps->i2c_protocol = true;
> +
>  	ret = tps6598x_read32(tps, TPS_REG_STATUS, &status);
>  	if (ret < 0)
>  		return ret;
> -- 
> 2.17.0
>
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