linux-kernel - Re: [PATCH 3/6] i3c: master: svc: fix ibi may not return mandatory data byte

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Message-ID: <20231017162707.187bebcf@xps-13>
Date:   Tue, 17 Oct 2023 16:27:07 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Frank Li <Frank.Li@....com>
Cc:     conor.culhane@...vaco.com, alexandre.belloni@...tlin.com,
        joe@...ches.com, linux-i3c@...ts.infradead.org,
        linux-kernel@...r.kernel.org, imx@...ts.linux.dev
Subject: Re: [PATCH 3/6] i3c: master: svc: fix ibi may not return mandatory
 data byte

Hi Frank,

Frank.Li@....com wrote on Mon, 16 Oct 2023 11:32:29 -0400:

> MSTATUS[RXPEND] is only updated after the data transfer cycle started. This
> creates an issue when the I3C clock is slow, and the CPU is running fast
> enough that MSTATUS[RXPEND] may not be updated when the code reach checking
> point. As a result, mandatory data are being missed.

					can be missed.

> Add a wait for MSTATUS[COMPLETE] to ensure that all mandatory data already
> in FIFO.

is already in the FIFO

> 
> Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/i3c/master/svc-i3c-master.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 0f57a5f75e39..c252446b2bc5 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -331,6 +331,7 @@ static int svc_i3c_master_handle_ibi(struct svc_i3c_master *master,
>  	struct i3c_ibi_slot *slot;
>  	unsigned int count;
>  	u32 mdatactrl;
> +	int ret, val;
>  	u8 *buf;
>  
>  	slot = i3c_generic_ibi_get_free_slot(data->ibi_pool);
> @@ -340,6 +341,13 @@ static int svc_i3c_master_handle_ibi(struct svc_i3c_master *master,
>  	slot->len = 0;
>  	buf = slot->data;
>  
> +	ret = readl_relaxed_poll_timeout(master->regs + SVC_I3C_MSTATUS, val,
> +						SVC_I3C_MSTATUS_COMPLETE(val), 0, 1000);

Are you sure !MSTATUS_COMPLETE(val) is never a valid condition?
Especially with non-mandatory bytes?

Also, are you sure of the indentation here?

> +	if (ret) {
> +		dev_err(master->dev, "Timeout when polling for COMPLETE\n");
> +		return ret;
> +	}
> +
>  	while (SVC_I3C_MSTATUS_RXPEND(readl(master->regs + SVC_I3C_MSTATUS))  &&
>  	       slot->len < SVC_I3C_FIFO_SIZE) {
>  		mdatactrl = readl(master->regs + SVC_I3C_MDATACTRL);


Thanks,
Miquèl