Re: [PATCH 1/5] i3c: master: Move rstdaa error suppression

[Jorge Marques]

On Mon, Mar 09, 2026 at 01:39:36PM +0200, Adrian Hunter wrote:
> On 08/03/2026 18:47, Jorge Marques wrote:
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -1016,6 +1016,10 @@ static int i3c_master_rstdaa_locked(struct i3c_master_controller *master,
> >  	ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
> >  	i3c_ccc_cmd_dest_cleanup(&dest);
> >  
> > +	/* No active devices on the bus. */
> > +	if (ret && cmd.err == I3C_ERROR_M2)
> > +		ret = 0;
> > +
> >  	return ret;
> >  }
> >  
> > @@ -1785,7 +1789,6 @@ i3c_master_register_new_i3c_devs(struct i3c_master_controller *master)
> >   */
> >  int i3c_master_do_daa_ext(struct i3c_master_controller *master, bool rstdaa)
> >  {
> > -	int rstret = 0;
> >  	int ret;
> >  
> >  	ret = i3c_master_rpm_get(master);
> > @@ -1795,9 +1798,9 @@ int i3c_master_do_daa_ext(struct i3c_master_controller *master, bool rstdaa)
> >  	i3c_bus_maintenance_lock(&master->bus);
> >  
> >  	if (rstdaa) {
> > -		rstret = i3c_master_rstdaa_locked(master, I3C_BROADCAST_ADDR);
> > -		if (rstret == I3C_ERROR_M2)
> > -			rstret = 0;
> > +		ret = i3c_master_rstdaa_locked(master, I3C_BROADCAST_ADDR);
> > +		if (ret)
> > +			goto out;
> 
> This is an unrelated change.  The original intention was to perform
> DAA even if RSTDAA fails.  If you really want this, it needs to be
> a separate patch with separate justification.
> 
> >  	}
Hi Adrian, handling I3C_ERROR_M2 is unchanged.

The intention is to perform the DAA if the RSTDAA fail due to a
I3C_ERROR_M2, this behaviour is unchanged, the duplicated error
suppression was moved from the do_daa call to inside
i3c_master_rstdaa_locked, and added a comment to explaining why it is okay
to fail: the i3c controller may probe, without any active i3c device on
the bus to acknowledge the CCC broadcast transfer.

The core purpose of the series is to fix the accidental propagation of
Mx error codes where 0 or negative errors are expected, to achieve this,
the error suppression have been moved to scopes that contain cmd.err and
clarified why they exist in the first place, to not have "ret = cmd.err"
anymore.

There are three exceptions all related to the bus initialization:
* RSTDAA -> i3c_master_rstdaa_locked
* ENTDAA -> i3c_master_entdaa_locked
* DISEC (broadcast address only) -> i3c_master_enec_disec_locked

I was actually wondering if it wouldn't be more adequate to call a
"probe bus" broadcast CCC that would be the only acceptable to return
I3C_ERROR_M2, and if so, we don't do the RSTDAA,DISEC at all (no i3c
devices, why continue?). But since ENTDAA suppression is still needed,
because the DAA always ends in NACK and the specification doesn't
specify if the RTL should suppress an I3C_ERROR_M2 after the ENTDAA
initial ACK, the benefits are minimal.

Best regards,
Jorge