Re: [PATCH v4 1/6] i3c: add addr and lvr to i2c_dev_desc structure

Boris Brezillon
2019-04-02T11:53:46Z

On Tue, 2 Apr 2019 12:32:41 +0100
vitor <vitor.soares@synopsys.com> wrote:

> On 02/04/19 12:22, Przemyslaw Gaj wrote:
> > Hi,
> >
> > The 04/02/2019 12:10, vitor wrote:
> >> Hi,
> >>
> >>
> >> On 01/04/19 20:24, Boris Brezillon wrote:
> >>> On Mon, 1 Apr 2019 19:48:45 +0100
> >>> vitor <vitor.soares@synopsys.com> wrote:
> >>>
> >>>> Hi,
> >>>>
> >>>> On 01/04/19 19:31, Boris Brezillon wrote:
> >>>>> On Mon, 1 Apr 2019 19:17:03 +0100
> >>>>> vitor <vitor.soares@synopsys.com> wrote:
> >>>>>
> >>>>>> Hi,
> >>>>>>
> >>>>>> On 30/03/19 14:36, Boris Brezillon wrote:
> >>>>>>> On Sun, 10 Mar 2019 13:58:38 +0000
> >>>>>>> Przemyslaw Gaj <pgaj@cadence.com> wrote:
> >>>>>>>
> >>>>>>>> I need to store address and lvr value for I2C devices without static definition
> >>>>>>>> in DT. This allows secondary master to transmit DEFSLVS command properly.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Przemyslaw Gaj <pgaj@cadence.com>
> >>>>>>>> ---
> >>>>>>>> include/linux/i3c/master.h | 5 +++++
> >>>>>>>> 1 file changed, 5 insertions(+)
> >>>>>>>>
> >>>>>>>> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> >>>>>>>> index eca8337..3c27d9f 100644
> >>>>>>>> --- a/include/linux/i3c/master.h
> >>>>>>>> +++ b/include/linux/i3c/master.h
> >>>>>>>> @@ -71,6 +71,9 @@ struct i2c_dev_boardinfo {
> >>>>>>>> * @common: common part of the I2C device descriptor
> >>>>>>>> * @boardinfo: pointer to the boardinfo attached to this I2C device
> >>>>>>>> * @dev: I2C device object registered to the I2C framework
> >>>>>>>> + * @addr: I2C device address
> >>>>>>>> + * @lvr: LVR (Legacy Virtual Register) needed by the I3C core to know about
> >>>>>>>> + * the I2C device limitations
> >>>>>>>> *
> >>>>>>>> * Each I2C device connected on the bus will have an i2c_dev_desc.
> >>>>>>>> * This object is created by the core and later attached to the controller
> >>>>>>>> @@ -84,6 +87,8 @@ struct i2c_dev_desc {
> >>>>>>>> struct i3c_i2c_dev_desc common;
> >>>>>>>> const struct i2c_dev_boardinfo *boardinfo;
> >>>>>>>> struct i2c_client *dev;
> >>>>>>>> + u16 addr;
> >>>>>>>> + u8 lvr;
> >>>>>>> You also need to remove lvr from i2c_dev_boardinfo and adjust the code
> >>>>>>> to use i2c_dev_desc->addr and i2c_dev_desc->lvr in this patch, not in
> >>>>>>> patch 3.
> >>>>>>>
> >>>>>> Why can't we keep the lvr and addr in i2c_dev_boardinfo and need this information on i2c_dev_desc?
> >>>>> Because i2c_dev_boardinfo is extracted from the DT and the secondary
> >>>>> slaves does not necessarily have this description. The idea is to keep
> >>>>> reserving the address slot for the I2C device even if we don't expose
> >>>>> it to the upper layers.
> >>>> So you are using i2c_dev_boardinfo just for DT devices?
> >>> All devices that are described in some way, can be through DT, ACPI or
> >>> board-file desc (only DT is supported right now, but we can easily add
> >>> support for other formats).
> >> We can drop i2c_dev_boardinfo.
> >>
> > Why you think we can drop it? We are still using it for DT devices.
>
> Until now you need it to hold LVR, if you pass it to i2c_dev_desc, the i2c_board_info can be used for DT.

It also contains a list node which we need to attach the object to the
i2c boardinfo list. Anyway, looks like I was wrong and
i2c_board_info->lvr is still needed.

>
> >
> >>>> Because at end we need to register the new i2c devs.
> >>> No, only those that have a valid description, because there's nothing
> >>> you can expose if you only have the address and LVR values. You at
> >>> least need to know which driver this dev should be attached to
> >>> (compatible string in your DT) and most drivers also need extra
> >>> information (basically all the DT props that are described a the DT
> >>> binding).
> >> In any case the HC need to know the bus mode, how is this done?
> > LVR is passed through DEFSLVS command.
>
> Is HC driver who set the bus mode? Shouldn't be the subsystem when you register all devices?
>

The framework selects the mode based on the devices attached to the bus.
The reception of a DEFSLVS frame should trigger the creation of I3C/I2C
devices which will in turn update the bus mode. Of course, the HC
driver must update the bus config accordingly.