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

[Lukasz Majewski]

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)?

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
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