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

[Jarkko Nikula]

On 04/25/2016 06:04 PM, Lucas De Marchi wrote:
> 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:
It reads above, bit 2 instead of 1 for TX FIFO checking and then either 
bit 5 or 0 for activity checking.

I'd say it's probably better to check bit 5 instead of bit 0 even bit 0 
is or'ed from bits 5 and 6. I don't know how possible slave support and 
slave being active will play here so it's best to follow spec.

--
jarkko