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

[Heiko Schocher]

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 ...

bye
Heiko
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