[PATCH v1 1/2] i3c: master: svc: Use manual response for IBI events

Stanley Chu
2025-08-28T09:35:19Z

From: Stanley Chu <yschu@nuvoton.com>

Driver wants to nack the IBI request when the target is not in the
known address list. In below code, svc_i3c_master_nack_ibi() will
cause undefined behavior when using AUTOIBI with auto response rule,
because hw always auto ack the IBI request.

switch (ibitype) {
case SVC_I3C_MSTATUS_IBITYPE_IBI:
dev = svc_i3c_master_dev_from_addr(master, ibiaddr);
if (!dev || !is_events_enabled(master, SVC_I3C_EVENT_IBI))
svc_i3c_master_nack_ibi(master);
...
break;

AutoIBI has another issue that the controller doesn't quit AutoIBI state
after IBIWON polling timeout when there is a SDA glitch(high->low->high).
1. SDA high->low: raising an interrupt to execute IBI ISR
2. SDA low->high
3. Driver writes an AutoIBI request
4. AutoIBI process does not start because SDA is not low
5. IBIWON polling times out
6. Controller reamins in AutoIBI state and doesn't accept EmitStop request

Emitting broadcast address with IBIRESP_MANUAL avoids both issues.

Signed-off-by: Stanley Chu <yschu@nuvoton.com>
---
drivers/i3c/master/svc-i3c-master.c | 28 +++++++++++++++++++++++-----
1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index 701ae165b25b..baf3059fd668 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -517,9 +517,22 @@ static void svc_i3c_master_ibi_isr(struct svc_i3c_master *master)
*/
writel(SVC_I3C_MINT_IBIWON, master->regs + SVC_I3C_MSTATUS);

- /* Acknowledge the incoming interrupt with the AUTOIBI mechanism */
- writel(SVC_I3C_MCTRL_REQUEST_AUTO_IBI |
- SVC_I3C_MCTRL_IBIRESP_AUTO,
+ /*
+ * Write REQUEST_START_ADDR request to emit broadcast address for arbitration,
+ * instend of using AUTO_IBI.
+ *
+ * Using AutoIBI request may cause controller to remain in AutoIBI state when
+ * there is a glitch on SDA line (high->low->high).
+ * 1. SDA high->low, raising an interrupt to execute IBI isr.
+ * 2. SDA low->high.
+ * 3. IBI isr writes an AutoIBI request.
+ * 4. The controller will not start AutoIBI process because SDA is not low.
+ * 5. IBIWON polling times out.
+ * 6. Controller reamins in AutoIBI state and doesn't accept EmitStop request.
+ */
+ writel(SVC_I3C_MCTRL_REQUEST_START_ADDR |
+ SVC_I3C_MCTRL_IBIRESP_MANUAL |
+ SVC_I3C_MCTRL_ADDR(I3C_BROADCAST_ADDR),
master->regs + SVC_I3C_MCTRL);

/* Wait for IBIWON, should take approximately 100us */
@@ -539,10 +552,15 @@ static void svc_i3c_master_ibi_isr(struct svc_i3c_master *master)
switch (ibitype) {
case SVC_I3C_MSTATUS_IBITYPE_IBI:
dev = svc_i3c_master_dev_from_addr(master, ibiaddr);
- if (!dev || !is_events_enabled(master, SVC_I3C_EVENT_IBI))
+ if (!dev || !is_events_enabled(master, SVC_I3C_EVENT_IBI)) {
svc_i3c_master_nack_ibi(master);
- else
+ } else {
+ if (dev->info.bcr & I3C_BCR_IBI_PAYLOAD)
+ svc_i3c_master_ack_ibi(master, true);
+ else
+ svc_i3c_master_ack_ibi(master, false);
svc_i3c_master_handle_ibi(master, dev);
+ }
break;
case SVC_I3C_MSTATUS_IBITYPE_HOT_JOIN:
if (is_events_enabled(master, SVC_I3C_EVENT_HOTJOIN))