Re: [PATCH] i2c: designware: do not disable adapter after transfer

[Lucas De Marchi]

On 04/25/2016 08:51 AM, Jarkko Nikula wrote:

[ ... ]

> > @@ -413,8 +416,16 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
> >       struct i2c_msg *msgs = dev->msgs;
> >       u32 ic_con, ic_tar = 0;
> >
> > -    /* Disable the adapter */
> > -    __i2c_dw_enable(dev, false);
> > +    if (dev->enabled) {
> > +        u32 ic_status;
> > +
> > +        /* check ic_tar and ic_con can be dynamically updated */
> > +        ic_status = dw_readl(dev, DW_IC_STATUS);
> > +        if (ic_status & DW_IC_STATUS_ACTIVITY
> > +            || !(ic_status & DW_IC_STATUS_TX_EMPTY)) {
> > +            __i2c_dw_enable(dev, false);
> > +        }
> > +    }
> Worth to double check this. I see bit 1 means TX FIFO not full and bit 2
> is TX FIFO completely empty.

the conditions to be able to update IC_TAR dynamically are:

  - Adapter isn't doing any TX/RX operation (IC_STATUS[5] == 0) and
  - There are no entries in TX FIFO (IC_STATUS[2] == 1)

So... yeah, the condition above seems wrong. I should be reading bit 5, 
not bit 1. Thanks! However:

IC_STATUS[5] signals activity for master mode
IC_STATUS[6] signals activity for slave mode
IC_STATUS[0] is IC_STATUS[5]|IC_STATUS[6]

And this controller is never in slave mode, only master mode, so it 
should be equivalent.

I wonder if I even have to check bit 5 since AFAICS we wouldn't be able 
to even call this function if there were any operation on tx/rx.

> Otherwise I'm fine with the patch as long as it works for Christian.

Anyway, I'll re-test with bit 5 checked and send an update.


Lucas De Marchi