[U-Boot] [PATCH 1/2] dm: i2c: Add a flag that need generate stop bit

[Lukasz Majewski]

On Mon, 17 Jun 2019 21:12:40 +0800
Chuanhua Han <chuanhua.han at nxp.com> wrote:

> Usually the i2c bus needs to write the address of the register before
> reading the internal register data of the device (ignoring the
> transmission of the slave address).
> 
> Generally, the stop signal is not needed before the register is read,
> but there is a special chip that needs this stop signal (such as
> pcf2127). However, in the current i2c general code, the dm_i2c_read
> api encapsulates two messages, the first time is to set the register
> address message, the second time is a message to read the register
> data, so that no stop signal is generated.
> 
> This patch uses the DM_I2C_CHIP_ADDR_STOP flag for specific
> i2c chips, so if the i2c slave requires a stop signal, chips driver
> can set this flag, then call the dm_i2c_write to set the register
> address (a stop signal is generated after this API call), then call
> dm_i2c_read to read the register data.
> 
> Signed-off-by: Chuanhua Han <chuanhua.han at nxp.com>

Reviewed-by: Lukasz Majewski <lukma at denx.de>

> ---
> Changes in v4:
> 	- Replace DM_I2C_CHIP_RD_NO_I2C_SETUP_OFFSET with
> DM_I2C_CHIP_ADDR_STOP.
> 
> Changes in v3:
> 	- Use the new flag DM_I2C_CHIP_RD_NO_I2C_SETUP_OFFSET	
> 
> Changes in v2: 
>         - Split the original patch into 3 patches
>         - Add detailed description information for each patch
> 
>  drivers/i2c/i2c-uclass.c | 6 ++++--
>  include/i2c.h            | 1 +
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
> index e47abf1833..9804b5e8c7 100644
> --- a/drivers/i2c/i2c-uclass.c
> +++ b/drivers/i2c/i2c-uclass.c
> @@ -135,8 +135,10 @@ int dm_i2c_read(struct udevice *dev, uint
> offset, uint8_t *buffer, int len) if (chip->flags &
> DM_I2C_CHIP_RD_ADDRESS) return i2c_read_bytewise(dev, offset, buffer,
> len); ptr = msg;
> -	if (!i2c_setup_offset(chip, offset, offset_buf, ptr))
> -		ptr++;
> +	if (!(chip->flags & DM_I2C_CHIP_ADDR_STOP)) {
> +		if (!i2c_setup_offset(chip, offset, offset_buf, ptr))
> +			ptr++;
> +	}
>  
>  	if (len) {
>  		ptr->addr = chip->chip_addr;
> diff --git a/include/i2c.h b/include/i2c.h
> index a5c760c711..3123cbf280 100644
> --- a/include/i2c.h
> +++ b/include/i2c.h
> @@ -28,6 +28,7 @@ enum dm_i2c_chip_flags {
>  	DM_I2C_CHIP_10BIT	= 1 << 0, /* Use 10-bit addressing
> */ DM_I2C_CHIP_RD_ADDRESS	= 1 << 1, /* Send address for each
> read byte */ DM_I2C_CHIP_WR_ADDRESS	= 1 << 2, /* Send address
> for each write byte */
> +	DM_I2C_CHIP_ADDR_STOP  = 1 << 3, /* Need generate stop bit */
>  };
>  
>  struct udevice;




Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
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