linux-kernel - Re: [PATCH] pwm: meson: Simplify probe function with dev_err

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Date:   Thu, 18 Aug 2022 09:45:39 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     zhaoxiao <zhaoxiao@...ontech.com>
Cc:     thierry.reding@...il.com, narmstrong@...libre.com,
        khilman@...libre.com, jbrunet@...libre.com,
        martin.blumenstingl@...glemail.com, linux-pwm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pwm: meson: Simplify probe function with dev_err_probe()

On Thu, Aug 18, 2022 at 03:22:34PM +0800, zhaoxiao wrote:
> Switch to dev_err_probe() to remove all dev_err() -> return repeated
> patterns, simplifying and shortening the probe function.
> 
> Signed-off-by: zhaoxiao <zhaoxiao@...ontech.com>
> ---
>  drivers/pwm/pwm-meson.c | 53 ++++++++++++++---------------------------
>  1 file changed, 18 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> index 57112f438c6d..43ce8d9a33d2 100644
> --- a/drivers/pwm/pwm-meson.c
> +++ b/drivers/pwm/pwm-meson.c
> @@ -126,20 +126,16 @@ static int meson_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
>  
>  	if (channel->clk_parent) {
>  		err = clk_set_parent(channel->clk, channel->clk_parent);
> -		if (err < 0) {
> -			dev_err(dev, "failed to set parent %s for %s: %d\n",
> +		if (err < 0)
> +			return dev_err_probe(dev, err, "failed to set parent %s for %s\n",
>  				__clk_get_name(channel->clk_parent),
> -				__clk_get_name(channel->clk), err);
> -			return err;
> -		}
> +				__clk_get_name(channel->clk));
>  	}
>  
>  	err = clk_prepare_enable(channel->clk);
> -	if (err < 0) {
> -		dev_err(dev, "failed to enable clock %s: %d\n",
> -			__clk_get_name(channel->clk), err);
> -		return err;
> -	}
> +	if (err < 0)
> +		return dev_err_probe(dev, err, "failed to enable clock %s\n",
> +			__clk_get_name(channel->clk));

It's wrong to use dev_err_probe in .request(). The function is only
supposed to be used in the .probe() call.

>  	return 0;
>  }
> @@ -166,24 +162,18 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
>  		duty = period - duty;
>  
>  	fin_freq = clk_get_rate(channel->clk);
> -	if (fin_freq == 0) {
> -		dev_err(meson->chip.dev, "invalid source clock frequency\n");
> -		return -EINVAL;
> -	}
> +	if (fin_freq == 0)
> +		return dev_err_probe(meson->chip.dev, -EINVAL, "invalid source clock frequency\n");
>  
>  	dev_dbg(meson->chip.dev, "fin_freq: %lu Hz\n", fin_freq);
>  
>  	pre_div = div64_u64(fin_freq * (u64)period, NSEC_PER_SEC * 0xffffLL);
> -	if (pre_div > MISC_CLK_DIV_MASK) {
> -		dev_err(meson->chip.dev, "unable to get period pre_div\n");
> -		return -EINVAL;
> -	}
> +	if (pre_div > MISC_CLK_DIV_MASK)
> +		return dev_err_probe(meson->chip.dev, -EINVAL, "unable to get period pre_div\n");
>  
>  	cnt = div64_u64(fin_freq * (u64)period, NSEC_PER_SEC * (pre_div + 1));
> -	if (cnt > 0xffff) {
> -		dev_err(meson->chip.dev, "unable to get period cnt\n");
> -		return -EINVAL;
> -	}
> +	if (cnt > 0xffff)
> +		return dev_err_probe(meson->chip.dev, -EINVAL, "unable to get period cnt\n");
>  
>  	dev_dbg(meson->chip.dev, "period=%u pre_div=%u cnt=%u\n", period,
>  		pre_div, cnt);
> @@ -200,10 +190,8 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
>  		/* Then check is we can have the duty with the same pre_div */
>  		duty_cnt = div64_u64(fin_freq * (u64)duty,
>  				     NSEC_PER_SEC * (pre_div + 1));
> -		if (duty_cnt > 0xffff) {
> -			dev_err(meson->chip.dev, "unable to get duty cycle\n");
> -			return -EINVAL;
> -		}
> +		if (duty_cnt > 0xffff)
> +			return dev_err_probe(meson->chip.dev, -EINVAL, "unable to get duty cycle\n");
>  
>  		dev_dbg(meson->chip.dev, "duty=%u pre_div=%u duty_cnt=%u\n",
>  			duty, pre_div, duty_cnt);
> @@ -509,11 +497,8 @@ static int meson_pwm_init_channels(struct meson_pwm *meson)
>  		channel->mux.hw.init = &init;
>  
>  		channel->clk = devm_clk_register(dev, &channel->mux.hw);
> -		if (IS_ERR(channel->clk)) {
> -			err = PTR_ERR(channel->clk);
> -			dev_err(dev, "failed to register %s: %d\n", name, err);
> -			return err;
> -		}
> +		if (IS_ERR(channel->clk))
> +			return dev_err_probe(dev, PTR_ERR(channel->clk), "failed to register %s\n", name);

This is the first conversion that is OK, as meson_pwm_init_channels() is
(only) called by meson_pwm_probe().

>  
>  		snprintf(name, sizeof(name), "clkin%u", i);

Here follows another return that could benefit for a conversion to
dev_err_probe. Currently it only returns an error code and doesn't emit
a message, but a message would be good.

> @@ -550,10 +535,8 @@ static int meson_pwm_probe(struct platform_device *pdev)
>  		return err;
>  
>  	err = devm_pwmchip_add(&pdev->dev, &meson->chip);
> -	if (err < 0) {
> -		dev_err(&pdev->dev, "failed to register PWM chip: %d\n", err);
> -		return err;
> -	}
> +	if (err < 0)
> +		return dev_err_probe(&pdev->dev, err, "failed to register PWM chip\n");
>  
>  	return 0;
>  }

This hunk is fine.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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