Messages in this thread | | | Date | Wed, 30 Aug 2023 10:52:11 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH 2/2] i3c: master: svc: fix probe failure when no i3c device exist |
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Hi Frank,
Frank.li@nxp.com wrote on Tue, 29 Aug 2023 11:26:42 -0400:
> On Tue, Aug 29, 2023 at 11:16:11AM +0200, Miquel Raynal wrote: > > Hi Frank, > > > > Frank.Li@nxp.com wrote on Mon, 28 Aug 2023 15:25:02 -0400: > > > > > If there are not i3c device, all ccc command will get NACK. Set > > > > no NACKed? > > > > > i3c_ccc_cmd::err as I3C_ERROR_M2. > > > > This sentence should come last and be slightly more explicit. > > > > > Return success when no i3c device found at svc_i3c_master_do_daa_locked(). > > > > Please explain why this is important/useful. > > If return failure, driver will probe failure when there are no any i3c > devices. I3C master supposed support hot join. The probe failure don't > make sense if no i3c devices found when master driver probe. > > How about rewrite commit log as
Much better, let me propose something slightly clearer.
> "I3C master supports device hot join, it doesn't make sense master driver > probe failure when there are no I3C devices. > > When there are no I3C devices attached, all CCC commands are NACKed. So > SVC I3C master fails to probe.
What about:
I3C masters are expected to support hot-join. This means at initialization time we might not yet discover any device and this should not be treated as a fatal error.
During the DAA procedure which happens at probe time, if no device has joined, all CCC will be NACKed (from a bus perspective). This leads to an early return with an error code which fails the probe of the master.
Let's avoid this by just telling the core through an I3C_ERROR_M2 return command code that no device was discovered, which is a valid situation. This way the master will no longer bail out and fail to probe for a wrong reason.
> Set i3c_cc_cmd:err as I3C_ERROR_M2. So I3C master framework > i3c_master_rstdaa_locked() can return expected ERROR code and continue > driver probe process. > > Return success at svc_i3c_master_do_daa_locked() if no i3c devices found. > So SVC master driver can probe successfully even if no I3C devices are > attached" > > > > > > Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver") > > > > Shall we consider a backport into stable kernels? > > Yes, I can add stable tag at next version.
Yes, please.
> > > > > Signed-off-by: Frank Li <Frank.Li@nxp.com> > > > --- > > > drivers/i3c/master/svc-i3c-master.c | 13 +++++++++++-- > > > 1 file changed, 11 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c > > > index 770b40e28015e..a5620103acb73 100644 > > > --- a/drivers/i3c/master/svc-i3c-master.c > > > +++ b/drivers/i3c/master/svc-i3c-master.c > > > @@ -789,6 +789,9 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master, > > > */ > > > break; > > > } else if (SVC_I3C_MSTATUS_NACKED(reg)) { > > > + /* No I3C devices attached */ > > > + if (dev_nb == 0) > > > + break; > > > > \n ? > > > > > /* > > > * A slave device nacked the address, this is > > > * allowed only once, DAA will be stopped and > > > @@ -1263,11 +1266,17 @@ static int svc_i3c_master_send_ccc_cmd(struct i3c_master_controller *m, > > > { > > > struct svc_i3c_master *master = to_svc_i3c_master(m); > > > bool broadcast = cmd->id < 0x80; > > > + int ret; > > > > > > if (broadcast) > > > - return svc_i3c_master_send_bdcast_ccc_cmd(master, cmd); > > > + ret = svc_i3c_master_send_bdcast_ccc_cmd(master, cmd); > > > else > > > - return svc_i3c_master_send_direct_ccc_cmd(master, cmd); > > > + ret = svc_i3c_master_send_direct_ccc_cmd(master, cmd); > > > + > > > + if (ret) > > > + cmd->err = I3C_ERROR_M2; > > > + > > > + return ret; > > > } > > > > > > static int svc_i3c_master_priv_xfers(struct i3c_dev_desc *dev, > > > > > > Thanks, > > Miquèl
Thanks, Miquèl
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