linux-kernel - Re: [PATCH v2 3/3] i3c: master: svc: fix invalidate IBI type and miss call client IBI handler

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Message-ID: <20240507100424.611181f1@xps-13>
Date: Tue, 7 May 2024 10:04:24 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Frank Li <Frank.Li@....com>
Cc: alexandre.belloni@...tlin.com, conor.culhane@...vaco.com,
 imx@...ts.linux.dev, linux-i3c@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] i3c: master: svc: fix invalidate IBI type and
 miss call client IBI handler

Hi Frank,

Frank.Li@....com wrote on Mon,  6 May 2024 12:40:09 -0400:

> In an In-Band Interrupt (IBI) handle, the code logic is as follows:
> 
> 1: writel(SVC_I3C_MCTRL_REQUEST_AUTO_IBI | SVC_I3C_MCTRL_IBIRESP_AUTO,
> 	  master->regs + SVC_I3C_MCTRL);
> 
> 2: ret = readl_relaxed_poll_timeout(master->regs + SVC_I3C_MSTATUS, val,
>                                     SVC_I3C_MSTATUS_IBIWON(val), 0, 1000);
> 	...
> 3: ibitype = SVC_I3C_MSTATUS_IBITYPE(status);
>    ibiaddr = SVC_I3C_MSTATUS_IBIADDR(status);
> 
> SVC_I3C_MSTATUS_IBIWON may be set before step 1. Thus, step 2 will return
> immediately, and the I3C controller has not sent out the 9th SCL yet.
> Consequently, ibitype and ibiaddr are 0, resulting in an unknown IBI type
> occurrence and missing call I3C client driver's IBI handler.
> 
> A typical case is that SVC_I3C_MSTATUS_IBIWON is set when an IBI occurs
> during the controller send start frame in svc_i3c_master_xfer().
> 
> Clear SVC_I3C_MSTATUS_IBIWON before issue SVC_I3C_MCTRL_REQUEST_AUTO_IBI
> to fix this issue.
> 
> Cc: stable@...r.kernel.org
> Fixes: 5e5e3c92e748 ("i3c: master: svc: fix wrong data return when IBI happen during start frame")
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> 
> Notes:
>     Change from v1 to v2
>     - improve comments.
> 
>  drivers/i3c/master/svc-i3c-master.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 94e4954509558..032fe032ec433 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -415,6 +415,19 @@ static void svc_i3c_master_ibi_work(struct work_struct *work)
>  	int ret;
>  
>  	mutex_lock(&master->lock);
> +	/*
> +	 * IBIWON may be set before SVC_I3C_MCTRL_REQUEST_AUTO_IBI, causing
> +	 * readl_relaxed_poll_timeout() to return immediately. Consequently,
> +	 * ibitype will be 0 since it was last updated only after the 8th SCL
> +	 * cycle, leading to missed client IBI handlers.
> +	 *
> +	 * A typical scenario is when IBIWON occurs and bus arbitration is lost
> +	 * at svc_i3c_master_priv_xfers().
> +	 *
> +	 * Clear SVC_I3C_MINT_IBIWON before sending SVC_I3C_MCTRL_REQUEST_AUTO_IBI.
> +	 */

Thanks a lot.

Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks,
Miquèl