diff mbox series

[v2,1/3] i2c: imx-lpi2c: directly return ISR when detect a NACK

Message ID 20230724105546.1964059-1-carlos.song@nxp.com
State New
Headers
Series [v2,1/3] i2c: imx-lpi2c: directly return ISR when detect a NACK |

Commit Message

Carlos Song July 24, 2023, 10:55 a.m. UTC 
  From: Gao Pan <pandy.gao@nxp.com>

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@nxp.com>
Signed-off-by: Carlos Song <carlos.song@nxp.com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

Comments

Andi Shyti July 25, 2023, 11:55 p.m. UTC | #1 
Hi Carlos,

On Mon, Jul 24, 2023 at 06:55:44PM +0800, carlos.song@nxp.com wrote:
> From: Gao Pan <pandy.gao@nxp.com>
> 
> 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@nxp.com>
> Signed-off-by: Carlos Song <carlos.song@nxp.com>
> ---
>  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.

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
>
Carlos Song July 26, 2023, 7:58 a.m. UTC | #2 
Hi, Andi

> -----Original Message-----
> From: Andi Shyti <andi.shyti@kernel.org>
> Sent: Wednesday, July 26, 2023 7:55 AM
> To: Carlos Song <carlos.song@nxp.com>
> Cc: Aisheng Dong <aisheng.dong@nxp.com>; shawnguo@kernel.org;
> s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com; Clark
> Wang <xiaoning.wang@nxp.com>; Bough Chen <haibo.chen@nxp.com>;
> dl-linux-imx <linux-imx@nxp.com>; linux-i2c@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: [EXT] Re: [PATCH v2 1/3] i2c: imx-lpi2c: directly return ISR when detect
> a NACK
> 
> Caution: This is an external email. Please take care when clicking links or
> opening attachments. When in doubt, report the message using the 'Report this
> email' button
> 
> 
> Hi Carlos,
> 
> On Mon, Jul 24, 2023 at 06:55:44PM +0800, carlos.song@nxp.com wrote:
> > From: Gao Pan <pandy.gao@nxp.com>
> >
> > 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@nxp.com>
> > Signed-off-by: Carlos Song <carlos.song@nxp.com>
> > ---
> >  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
> >
diff mbox series

Patch

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;
+	} 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;
 }