linux-kernel - Re: [PATCH] i3c: master: svc: add NACK check after start byte sent

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Date:   Mon, 22 May 2023 10:33:27 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Clark Wang <xiaoning.wang@....com>
Cc:     conor.culhane@...vaco.com, alexandre.belloni@...tlin.com,
        linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i3c: master: svc: add NACK check after start byte sent

Hi Clark,

xiaoning.wang@....com wrote on Wed, 17 May 2023 11:30:30 +0800:

> Add NACK check after start byte is sent.
> It is possible to detect early that a device is not on the bus
> and avoid invalid transmissions thereafter.
> 
> Signed-off-by: Clark Wang <xiaoning.wang@....com>

Nice addition.

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

> ---
>  drivers/i3c/master/svc-i3c-master.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 4edf33ed207d..0d63b732ef0c 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -92,6 +92,7 @@
>  #define SVC_I3C_MINTCLR      0x094
>  #define SVC_I3C_MINTMASKED   0x098
>  #define SVC_I3C_MERRWARN     0x09C
> +#define   SVC_I3C_MERRWARN_NACK BIT(2)
>  #define SVC_I3C_MDMACTRL     0x0A0
>  #define SVC_I3C_MDATACTRL    0x0AC
>  #define   SVC_I3C_MDATACTRL_FLUSHTB BIT(0)
> @@ -1014,6 +1015,11 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
>  	if (ret)
>  		goto emit_stop;
>  
> +	if (readl(master->regs + SVC_I3C_MERRWARN) & SVC_I3C_MERRWARN_NACK) {
> +		ret = -ENXIO;
> +		goto emit_stop;
> +	}
> +
>  	if (rnw)
>  		ret = svc_i3c_master_read(master, in, xfer_len);
>  	else


Thanks,
Miquèl