linux-kernel - RE: [PATCH 12/12] i2c: xiic: Correct the BNB interrupt enable sequence

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Date:   Wed, 13 Jul 2022 08:02:18 +0000
From:   "Guntupalli, Manikanta" <manikanta.guntupalli@....com>
To:     Krzysztof Adamski <krzysztof.adamski@...ia.com>,
        Manikanta Guntupalli <manikanta.guntupalli@...inx.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "Simek, Michal" <michal.simek@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "git (AMD-Xilinx)" <git@....com>
CC:     Srinivas Goud <srinivas.goud@...inx.com>
Subject: RE: [PATCH 12/12] i2c: xiic: Correct the BNB interrupt enable
 sequence

Hi Krzysztof,

> -----Original Message-----
> From: Krzysztof Adamski <krzysztof.adamski@...ia.com>
> Sent: Wednesday, June 29, 2022 6:44 PM
> To: Manikanta Guntupalli <manikanta.guntupalli@...inx.com>;
> michal.simek@...inx.com; Simek, Michal <michal.simek@....com>; linux-
> arm-kernel@...ts.infradead.org; linux-i2c@...r.kernel.org; linux-
> kernel@...r.kernel.org; git (AMD-Xilinx) <git@....com>
> Cc: Srinivas Goud <srinivas.goud@...inx.com>
> Subject: Re: [PATCH 12/12] i2c: xiic: Correct the BNB interrupt enable
> sequence
> 
> CAUTION: This message has originated from an External Source. Please use
> proper judgment and caution when opening attachments, clicking links, or
> responding to this email.
> 
> 
> W dniu 24.06.2022 o 14:05, Manikanta Guntupalli pisze:
> > From: Srinivas Goud <srinivas.goud@...inx.com>
> >
> > With updated AXI IIC IP core(v2.1)there is change in IP behavior in
> > dynamic mode, where controller initiate read transfer on IIC bus only
> > after getting the value for the number of bytes to receive.
> >
> > In the existing xiic_start_recv function Bus Not Busy(BNB) interrupt
> > is enabled just after "slave address + start"
> > write to FIFO and before the "count + stop"write to FIFO.
> > Since IIC controller drives the start address of a transaction on the
> > bus only after it has received the byte count information the above
> > sequence can lead to spurious BNB interrupt in case there is any delay
> > after "slave address + start" write to FIFO.
> >
> > This is fixed by ensuring that BNB interrupt is enabled only after
> > "count + stop" has been written to FIFO.
> >
> > Signed-off-by: Srinivas Goud <srinivas.goud@...inx.com>
> > Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@...inx.com>
> > ---
> 
> [...]
> 
> Does this spurious interrupt cause any trouble or it is just ignored and the
> only problem is unneeded extra CPU load?
> 

No functional issue we just corrected the sequence as per IP changes.

> Krzysztof


Thanks,
Manikanta.