[PATCH v2 2/2] i3c: master: svc: fix probe failure when no i3c device exist

Frank Li
2023-08-30T14:17:59Z

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.

Cc: stable@vger.kernel.org
Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver")
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---

Notes:
Change from v1 to v2:
- rewrite commit message
- cc stable
- add empty line in daa()

drivers/i3c/master/svc-i3c-master.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 770b40e28015e..cf932ee056ef9 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -789,6 +789,10 @@ 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;
+
/*
* A slave device nacked the address, this is
* allowed only once, DAA will be stopped and
@@ -1263,11 +1267,17 @@ 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,
--
2.34.1