RE: [EXT] Re: [PATCH v2 1/3] i2c: imx-lpi2c: directly return ISR when detect a NACK

From: Carlos Song
Date: Wed Jul 26 2023 - 04:06:51 EST

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In reply to: Andi Shyti: "Re: [PATCH v2 1/3] i2c: imx-lpi2c: directly return ISR when detect a NACK"
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Hi, Andi

> -----Original Message-----
> From: Andi Shyti <andi.shyti@xxxxxxxxxx>
> Sent: Wednesday, July 26, 2023 7:55 AM
> To: Carlos Song <carlos.song@xxxxxxx>
> Cc: Aisheng Dong <aisheng.dong@xxxxxxx>; shawnguo@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; Clark
> Wang <xiaoning.wang@xxxxxxx>; Bough Chen <haibo.chen@xxxxxxx>;
> dl-linux-imx <linux-imx@xxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: [EXT] Re: [PATCH v2 1/3] i2c: imx-lpi2c: directly return ISR when detect
> a NACK
>
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>
> Hi Carlos,
>
> On Mon, Jul 24, 2023 at 06:55:44PM +0800, carlos.song@xxxxxxx wrote:
> > From: Gao Pan <pandy.gao@xxxxxxx>
> >
> > A NACK flag in ISR means i2c bus error. In such codition, there is no
> > need to do read/write operation. It's better to return ISR directly
> > and then stop i2c transfer.
> >
> > Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> > Signed-off-by: Gao Pan <pandy.gao@xxxxxxx>
> > Signed-off-by: Carlos Song <carlos.song@xxxxxxx>
> > ---
> > drivers/i2c/busses/i2c-imx-lpi2c.c | 11 +++++------
> > 1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > index c3287c887c6f..158de0b7f030 100644
> > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > @@ -514,15 +514,14 @@ static irqreturn_t lpi2c_imx_isr(int irq, void
> *dev_id)
> > temp = readl(lpi2c_imx->base + LPI2C_MSR);
> > temp &= enabled;
> >
> > - if (temp & MSR_RDF)
> > + if (temp & MSR_NDF) {
> > + complete(&lpi2c_imx->complete);
> > + return IRQ_HANDLED;
>
> you can actually remove the return here
>
> if (temp & MSR_NDF)
> complete();
> else if (temp & MSR_RDF)
> exfifo();
> else if (temp & MSR_TDF)
> txfifo();
>
> return IRQ_HANDLED;
>
>
> BTW, the logic here is changing, as well and it's not described in the commit log.
> This patch is not only stopping when a nack is received (MSR_NDF), but it's also
> making mutually exclusive read/write (which I guess are MSR_RDF and
> MSR_TDF).
>
> Is this what you want? If so, can you please describe it in the commit log or add
> a comment describing that the three states are all mutually exclusive.
>
Yes. That is ok. I will fix the commit log and send V3 patch.
> Thanks,
> Andi
>
>
> > + } else if (temp & MSR_RDF)
> > lpi2c_imx_read_rxfifo(lpi2c_imx);
> > -
> > - if (temp & MSR_TDF)
> > + else if (temp & MSR_TDF)
> > lpi2c_imx_write_txfifo(lpi2c_imx);
> >
> > - if (temp & MSR_NDF)
> > - complete(&lpi2c_imx->complete);
> > -
> > return IRQ_HANDLED;
> > }
> >
> > --
> > 2.34.1
> >