linux-kernel - Re: [PATCH] i2c: imx: fix divide by zero warning

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Message-ID: <Z0SxUhBmp06ScnfP@lizhi-Precision-Tower-5810>
Date: Mon, 25 Nov 2024 12:18:10 -0500
From: Frank Li <Frank.li@....com>
To: carlos.song@....com
Cc: o.rempel@...gutronix.de, kernel@...gutronix.de, andi.shyti@...nel.org,
	shawnguo@...nel.org, s.hauer@...gutronix.de, festevam@...il.com,
	linux-i2c@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx: fix divide by zero warning

On Mon, Nov 25, 2024 at 10:15:21PM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
>
> Add "i2c_clk_rate / 2" check to avoid "divide by zero warning".
> i2c_clk_rate may be zero if i2c clock is disabled.
>
> Signed-off-by: Carlos Song <carlos.song@....com>
> Signed-off-by: Clark Wang <xiaoning.wang@....com>
> Signed-off-by: Haibo Chen <haibo.chen@....com>
> ---

You sent this patch twice?

Reviewed-by: Frank Li <Frank.Li@....com>

>  drivers/i2c/busses/i2c-imx.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 2c782cdc26bd..5ed4cb61e262 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -623,8 +623,8 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
>  	return 0;
>  }
>
> -static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
> -			    unsigned int i2c_clk_rate)
> +static int i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
> +			   unsigned int i2c_clk_rate)
>  {
>  	struct imx_i2c_clk_pair *i2c_clk_div = i2c_imx->hwdata->clk_div;
>  	unsigned int div;
> @@ -639,7 +639,11 @@ static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
>
>  	/* Divider value calculation */
>  	if (i2c_imx->cur_clk == i2c_clk_rate)
> -		return;
> +		return 0;
> +
> +	/* Keep the denominator of the following program always NOT equal to 0. */
> +	if (!(i2c_clk_rate / 2))
> +		return -EINVAL;
>
>  	i2c_imx->cur_clk = i2c_clk_rate;
>
> @@ -670,6 +674,8 @@ static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
>  	dev_dbg(&i2c_imx->adapter.dev, "IFDR[IC]=0x%x, REAL DIV=%d\n",
>  		i2c_clk_div[i].val, i2c_clk_div[i].div);
>  #endif
> +
> +	return 0;
>  }
>
>  static int i2c_imx_clk_notifier_call(struct notifier_block *nb,
> @@ -679,11 +685,12 @@ static int i2c_imx_clk_notifier_call(struct notifier_block *nb,
>  	struct imx_i2c_struct *i2c_imx = container_of(nb,
>  						      struct imx_i2c_struct,
>  						      clk_change_nb);
> +	int ret = 0;
>
>  	if (action & POST_RATE_CHANGE)
> -		i2c_imx_set_clk(i2c_imx, ndata->new_rate);
> +		ret = i2c_imx_set_clk(i2c_imx, ndata->new_rate);
>
> -	return NOTIFY_OK;
> +	return notifier_from_errno(ret);
>  }
>
>  static int i2c_imx_start(struct imx_i2c_struct *i2c_imx, bool atomic)
> @@ -1782,7 +1789,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  		i2c_imx->bitrate = pdata->bitrate;
>  	i2c_imx->clk_change_nb.notifier_call = i2c_imx_clk_notifier_call;
>  	clk_notifier_register(i2c_imx->clk, &i2c_imx->clk_change_nb);
> -	i2c_imx_set_clk(i2c_imx, clk_get_rate(i2c_imx->clk));
> +	ret = i2c_imx_set_clk(i2c_imx, clk_get_rate(i2c_imx->clk));
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "can't get I2C clock\n");
> +		goto clk_notifier_unregister;
> +	}
>
>  	i2c_imx_reset_regs(i2c_imx);
>
> --
> 2.34.1
>