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

Frank Li
2025-08-29T01:39:00Z

On Thu, Aug 28, 2025 at 04:32:24PM +0800, Stanley Chu wrote:
> 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.
>

missed fix tag

> 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),

Suggest build full fields, although these bits is 0, like.
SVC_I3C_MCTRL_DIR()
SVC_I3C_MCTRL_TYPE_I3C

Frank

> 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))
> --
> 2.34.1
>
>
> --
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