[i2c] [PATCH 3/5] I2C: DaVinci: remove useless IVR read

[Troy Kisky]

Jean Delvare wrote:
> On Thu, 20 Mar 2008 20:06:08 -0700, Troy Kisky wrote:
>> Interrupts are enabled at the point where
>> the DAVINCI_I2C_IVR_REG is read, so unless
>> an interrupt happened just at that moment,
>> no interrupt would be pending. Even though
>> documentation implies you should do this,
>> I see no reason. If slave support is added,
>> this read would cause a hard to reproduce bug.
> 
> This is only a problem if the device can operate in master mode and
> slave mode concurrently. Is it the case? But even then, as you can't
> have master and slave activity going on at the same time on a given I2C
> bus, it only matters if some DaVinci boards have more than one i2c
> buses. Is it the case?
> 

There is only one i2c bus AFAIK, but how that is relevant escapes me.
And I realize that the host controller can not be master while it is
addressed as slave, but that does not prohibit a program from trying to
be master. Just because the interrupt that lets me know I am addressed
as slave is removed (and ignored,) the state of the bus is not suddenly
idle again. The documentation says to make sure no interrupts are pending
before starting a transfer. It should says "Service all pending interrupts, so
that the bus is idle before starting a transfer." The wait_bus_not_busy
will satisfy this in most cases. The exception being if the process is swapped
out, giving time for someone else on the bus to become master.


My removing the IVR read will not magically make the bus idle again either. But
at least, the interrupt routine will have a chance to do something.

Troy