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

[Boris Brezillon <boris.brezillon@collabora.com>]

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.

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