linux-kernel - Re: [PATCH] i2c: imx-lpi2c: directly return ISR when detect a NACK

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Message-ID: <20230614000841.frvf4n5zgh5eihmq@intel.intel>
Date:   Wed, 14 Jun 2023 02:08:41 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     carlos.song@....com
Cc:     aisheng.dong@....com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, xiaoning.wang@....com,
        haibo.chen@....com, linux-imx@....com, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx-lpi2c: directly return ISR when detect a NACK

Hi,

On Wed, May 24, 2023 at 10:40:02AM +0800, carlos.song@....com wrote:
> From: Gao Pan <pandy.gao@....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@....com>
> Signed-off-by: Carlos Song <carlos.song@....com>

looks good to me, just a little note.

> ---
>  drivers/i2c/busses/i2c-imx-lpi2c.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
> index 1af0a637d7f1..11240bf8e8e2 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -514,15 +514,17 @@ static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
>  	temp = readl(lpi2c_imx->base + LPI2C_MSR);
>  	temp &= enabled;
>  
> +	if (temp & MSR_NDF) {
> +		complete(&lpi2c_imx->complete);
> +		goto ret;
> +	}
> +
>  	if (temp & MSR_RDF)

else if () and remove goto and brackets. You have used the
"else if" below and we can keep it consistent.

This way the commit log should be a bit different as we
decide to check exclusively using else if's for the active bits.
This way we also stop processing the MSR register if a NACK is
received.

With the above I can give you a conditional r-b: are you able to
pull Dong into this review as Wolfram asked?

Thank you,
Andi

>  		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);
> -
> +ret:
>  	return IRQ_HANDLED;
>  }
>  
> -- 
> 2.34.1
>