RE: [PATCH v2 1/5] i3c: master: detach and free device if pre_assign_dyn_addr() fails

From: Przemyslaw Gaj <pgaj@cadence.com>
Date: Wed, Sep 04, 2019 at 05:47:18

The 09/03/2019 11:57, Vitor Soares wrote:

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EXTERNAL MAIL


From: Przemyslaw Gaj <pgaj@cadence.com>
Date: Tue, Sep 03, 2019 at 12:13:57

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Hi Vitor,

I'm sorry for the delay.

The 09/03/2019 12:35, Vitor Soares wrote:

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EXTERNAL MAIL


On pre_assing_dyn_addr() the devices that fail:
  i3c_master_setdasa_locked()
  i3c_master_reattach_i3c_dev()
  i3c_master_retrieve_dev_info()

are kept in memory and master->bus.devs list. This makes the i3c devices
without a dynamic address are sent on DEFSLVS CCC command. Fix this by
detaching and freeing the devices that fail on pre_assign_dyn_addr().

What is the problem with sending devices without dynamic address in DEFSLVS?

How do you address them?
For the DA field in DEFSLVS frame, the spec says: "shall contain the 
current value of the Slave's assigned 7-bit Dynamic address". If the 
device doesn't have the dynamic address assigned yet why send it?

What stops us from operating with this device in I2C mode using his SA?

So, send it as an I2C device as spec says.

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Shouldn't we still inform rest of the devices about that? About fact that
device with SA without DA exists on the bus?

I would like to understand what is the use case for this? 

Look above. I2C mode still should be possible IMO. Just consider the case when
you really need some information from that device, main master can assign
dynamic address later but you can make some transfers.

It is true, but again it is a I2C device and not I3C device. It won't 
reply to I3C commands until has a DA.
How will you know that the DA sent in DEFSLVS is not assigned yet?

I know our framework
does not support that case but secondary master can be different system which
should know that this device exists and don't have DA yet, so I2C mode is
available.

If the HJ happen in secondary master side, there is a change to describe 
in DT what should be DA. Please check 2nd patch.

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On I3C spec table "I3C Devices Roles vs Responsibilities", Secondary 
Master is not responsible to do Dynamic Address Assignment but it is 
optional to do Hot-Join Dynamic Address Assignment.

Yes, we discussed that few times during the review of Mastership patch series.

Hence, based on that table, secondary master won't do DAA just because he 
want, It needs a HJ to trigger DAA.
Sorry, but for me based on what spec says this use case is not feasible. 


Best regards,
Vitor Soares