linux-kernel - Re: [PATCH v3] pwm: vt8500: Update vt8500 PWM driver support

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Date:	Wed, 24 Oct 2012 00:14:19 +0200
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Tony Prisk <linux@...sktech.co.nz>
Cc:	devicetree-discuss@...ts.ozlabs.org, arm@...nel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] pwm: vt8500: Update vt8500 PWM driver support

On Tue, Oct 23, 2012 at 07:10:24AM +1300, Tony Prisk wrote:
[...]
> @@ -87,6 +98,11 @@ static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>  {
>  	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
>  
> +	if (!clk_enable(vt8500->clk)) {
> +		dev_err(chip->dev, "failed to enable clock\n");
> +		return -EBUSY;
> +	};
> +

I don't think that works. The clock API returns 0 on success and a
negative error code on failure. So this should rather be something like:

	err = clk_enable(vt8500->clk);
	if (err < 0) {
		dev_err(chip->dev, "failed to enable clock: %d\n", err);
		return err;
	}

> @@ -123,6 +153,12 @@ static int __devinit pwm_probe(struct platform_device *pdev)
>  	chip->chip.ops = &vt8500_pwm_ops;
>  	chip->chip.base = -1;
>  	chip->chip.npwm = VT8500_NR_PWMS;
> +	chip->clk = devm_clk_get(&pdev->dev, NULL);
> +

The blank line should go above the call to devm_clk_get().

> +	if (IS_ERR_OR_NULL(chip->clk)) {
> +		dev_err(&pdev->dev, "clock source not specified\n");
> +		return PTR_ERR(chip->clk);
> +	}
[...]
> +	if (!clk_prepare(chip->clk)) {
> +		dev_err(&pdev->dev, "failed to prepare clock\n");
> +		return -EBUSY;
> +	}
> +

Same comment here. I wonder how this code can work, since if the clock
is properly prepared, then it will return 0, and the above will return
-EBUSY.

>  	ret = pwmchip_add(&chip->chip);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to add pwmchip\n");

Error messages can be considered prose, so this should be: "failed to
add PWM chip".

Thierry

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