[U-Boot] ColdFire I2C implementing I2C idle [PATCH] -- resent in git format

[Joakim Tjernlund]

>
> Hello Michael,
>
> Thanks for posting your patches in plain text.
>
> Michael Durrant wrote:
> > drivers_i2c_fsl_i2c.patch
> >    - need to set I2C to be idle according to the MCF5282 user's manual
> >
> >    If I2SR[IBB] is set when the I2C bus module is enabled,
> >    execute the following code sequence before proceeding with
> >    normal initialization code. This issues a STOP command to the
> >    slave device, placing it in idle state as if it were just
> >    power-cycled on.
> >
> >    I2CR = 0x0
> >    I2CR = 0xA
> >    dummy read of I2DR
> >    I2SR = 0x0
> >    I2CR = 0x0
> >
> > Signed-off-by: David Wu <davidwu at arcturusnetworks.com>
> > Signed-off-by: Michael Durrant <mdurrant at arcturusnetworks.com>
> > ---
> >  drivers/i2c/fsl_i2c.c |   13 +++++++++++++
> >  1 files changed, 13 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
> > index 2241990..bce750c 100644
> > --- a/drivers/i2c/fsl_i2c.c
> > +++ b/drivers/i2c/fsl_i2c.c
> > @@ -251,12 +251,25 @@ i2c_init(int speed, int slaveadd)
> >  #endif
> >  }
> >
> > +static __inline__ int i2c_set_idle(void)
> > +{
> > +    writeb(0, &i2c_dev[i2c_bus_num]->cr);
> > +    writeb(I2C_CR_MEN | I2C_CR_MSTA, &i2c_dev[i2c_bus_num]->cr);
> > +    readb(&i2c_dev[i2c_bus_num]->dr);
> > +    writeb(0, &i2c_dev[i2c_bus_num]->sr);
> > +    writeb(0, &i2c_dev[i2c_bus_num]->cr);
> > +    writeb(I2C_CR_MEN, &i2c_dev[i2c_bus_num]->cr);
> > +}
> > +
> >  static int
> >  i2c_wait4bus(void)
> >  {
> >      unsigned long long timeval = get_ticks();
> >      const unsigned long long timeout = usec2ticks(CONFIG_I2C_MBB_TIMEOUT);
> >
> > +    if (readb(&i2c_dev[i2c_bus_num]->sr) & I2C_SR_MBB)
> > +        i2c_set_idle();
> > +
> >      while (readb(&i2c_dev[i2c_bus_num]->sr) & I2C_SR_MBB) {
> >          if ((get_ticks() - timeval) > timeout)
> >              return -1;
>
> Hmm.. I can;t find this for example in the MPC8360ERM.pdf, which
> uses also this driver ... So I vote for activating this only,
> if this driver is used for  __M68K__ ...
>
> Also, you write, that this sequence is necessary before normal
> initialization code, but i2c_wait4bus() is called from i2c_read()
> and i2c_write(), so the I2C bus is long ago initialized ...
> or what do you mean with "normal initialization code" ?
>
> Also, whats with multimaster systems? Your code maybe cuts a running
> data transmission. The MPC8360ERM.pdf manual says "check the MBB bit,
> if the bus is free, before switching to master mode", thats what
> actual code did ... so, I want this only activated, if __M68K__
> is defined ...

All true. This cannot go in as is. What you need is a I2C reset sequence
as the above isn't enough in the general case. Michael, have a look at the
kernel driver, it has some fixup code you could borrow.

   Jocke