[U-Boot] [EXT] Re: [PATCH 1/2] dm: i2c: Add a flag that not call i2c_setup_offset

[Chuanhua Han]

> -----Original Message-----
> From: Lukasz Majewski <lukma at denx.de>
> Sent: 2019年6月4日 14:46
> To: Chuanhua Han <chuanhua.han at nxp.com>
> Cc: hs at denx.de; u-boot at lists.denx.de; Biwen Li <biwen.li at nxp.com>
> Subject: Re: [EXT] Re: [U-Boot] [PATCH 1/2] dm: i2c: Add a flag that not call
> i2c_setup_offset
> 
> On Tue, 4 Jun 2019 02:20:49 +0000
> Chuanhua Han <chuanhua.han at nxp.com> wrote:
> 
> > > -----Original Message-----
> > > From: Lukasz Majewski <lukma at denx.de>
> > > Sent: 2019年6月4日 6:08
> > > To: Chuanhua Han <chuanhua.han at nxp.com>
> > > Cc: hs at denx.de; u-boot at lists.denx.de; Biwen Li <biwen.li at nxp.com>
> > > Subject: [EXT] Re: [U-Boot] [PATCH 1/2] dm: i2c: Add a flag that not
> > > call i2c_setup_offset
> > >
> > > On Thu, 30 May 2019 18:31:48 +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_RD_NO_I2C_SETUP_OFFSET 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>
> > > > ---
> > > > 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_RD_NO_I2C_SETUP_OFFSET))
> > > > {
> > > > +		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 */
> > >
> > > Aren't those two above flags describe exactly what you need? They
> > > send address for each read/written byte. (or do you need to send
> > > more than a single byte)?
> > This is not what I need. I need to generate a stop signal after
> > setting the register address,
> 
> Please correct me if I'm wrong, but the above flag says that you need to send
> the I2C stop after you send one byte?
> 
> Would it be possible to send address with I2C stop and then read data (single
> byte) with I2C stop?
> 
> > so I need the following flag.
> > >
> > > >	DM_I2C_CHIP_RD_NO_I2C_SETUP_OFFSET  = 1 << 3,
> 
> I do find this name as a bit misleading - is the RD_NO_I2C_SETUP_OFFSET
> name reflecting the purpose (to send I2C stop after sending address)?
The purpose is to send a stop signal after setting the slave register address.
> 
> Maybe there would be a better name?
> 
> > > >       /* No i2c_setup_offset*/ };
> > > >
> > > >  struct udevice;
> > >
> > >
> > >
> > >
> > > Best regards,
> > >
> > > Lukasz Majewski
> > >
> > > --
> > >
> > > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > > lukma at denx.de
> 
> 
> 
> 
> Best regards,
> 
> Lukasz Majewski
> 
> --
> 
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma at denx.de