[U-Boot] [PATCH] 7/12 Multiadapter/multibus I2C, drivers part 4

[ksi at koi8.net]

On Thu, 19 Feb 2009, Heiko Schocher wrote:

> Hello Wolfgang,
> 
> Wolfgang Denk wrote:
> > Dear ksi at koi8.net,
> > 
> > In message <Pine.LNX.4.64ksi.0902181400470.5729 at home-gw.koi8.net> you wrote:
> >> How would you know what to initialize and what not to? We were initializing
> > 
> > I don't know. You probably need some way to encode some kind of
> 
> Look at my proposal for i2c_set_bus_num().
> 
> http://lists.denx.de/pipermail/u-boot/2009-February/047860.html
> 
> This function is the central point for switching between busses. It
> _must_ be called, when switching busses, so this function can decide,
> if the hardware adapter is initialized or not. If not, it will
> call the init function ... and there is no problem for calling
> the init function, when running in flash. We _first_ call the
> adapter specific init() function and _then_ switching the muxes.
> 
> Also we can do in this function the adapterspecific deinit()
> function ... one central point for doing init(), deinit()
> sounds good to me.
> 
> We just have to look, that boards who uses i2c_* functions,
> now call before accessing the I2C bus, i2c_set_bus_num().
> But this is with every implemntation for multibussuport a ToDo,
> because there probably now more then one bus, so we must
> take care of this.
> 
> >> It is easy to initialize just a selected set of adapters in the new code but
> >> how do we decide what to initialize and what not to?
> > 
> > Good question. Probably each  I2C  device  will  have  some  list  of
> > bus/adapter  ID's  that need to be up to access it, and that will get
> > shut down afterwards.
> 
> No need for this i2c_set_bus_num() will do that automagically.
> 
> >> Should we add a config option like CONFIG_I2C_INIT_ADAPTERS {1,3,5,9} ? But
> > 
> > No, because we probably do not need to activate all tehse adapters at
> > the same time.
> 
> We don;t need this, because there is i2c_set_bus_number, which can
> do this for us.
> 
> >> There is also no way of DE-initilizing those interfaces so that init is like
> >> a gun trigger -- once it is pulled, there is no way to bring the bullet
> >> back.
> > 
> > That needs to be changed, too.
> 
> Ack.

Sorry guys, I simply do not have THAT much time... I have my board coming
from assembly house so I'll probably end up with some board-specific hack;
that will be much faster.

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