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

[Chuanhua Han]

+ Simon Glass

> -----Original Message-----
> From: Lukasz Majewski <lukma at denx.de>
> Sent: 2019年6月18日 16:07
> To: Chuanhua Han <chuanhua.han at nxp.com>
> Cc: hs at denx.de; sjg at chromium.org; Biwen Li <biwen.li at nxp.com>;
> u-boot at lists.denx.de
> Subject: [EXT] Re: [PATCH 1/2] dm: i2c: Add a flag that need generate stop bit
> 
> 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
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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