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

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Message-ID: <aLChjRd65DG/xG1R@lizhi-Precision-Tower-5810>
Date: Thu, 28 Aug 2025 14:35:57 -0400
From: Frank Li <Frank.li@....com>
To: Stanley Chu <stanley.chuys@...il.com>
Cc: miquel.raynal@...tlin.com, alexandre.belloni@...tlin.com,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
	tomer.maimon@...oton.com, kwliu@...oton.com, yschu@...oton.com
Subject: Re: [PATCH v1 1/2] i3c: master: svc: Use manual response for IBI
 events

On Thu, Aug 28, 2025 at 04:32:24PM +0800, Stanley Chu wrote:
> From: Stanley Chu <yschu@...oton.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@...oton.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
>
>
> --
> linux-i3c mailing list
> linux-i3c@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-i3c

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