linux-kernel - Re: [PATCH v8 3/6] pwm: sun4i: Add an optional probe for bus clock

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Date:   Thu, 21 Nov 2019 22:05:59 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Philipp Zabel <pza@...gutronix.de>, linux-pwm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com,
        Jernej Skrabec <jernej.skrabec@...l.net>
Subject: Re: [PATCH v8 3/6] pwm: sun4i: Add an optional probe for bus clock

On Thu, Nov 21, 2019 at 08:58:59PM +0100, Clément Péron wrote:
> From: Jernej Skrabec <jernej.skrabec@...l.net>
> 
> H6 PWM core needs bus clock to be enabled in order to work.
> 
> Add an optional probe for it.
> 
> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> ---
>  drivers/pwm/pwm-sun4i.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 369990ae7d09..66befd8d6f9c 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -78,6 +78,7 @@ struct sun4i_pwm_data {
>  
>  struct sun4i_pwm_chip {
>  	struct pwm_chip chip;
> +	struct clk *bus_clk;
>  	struct clk *clk;
>  	struct reset_control *rst;
>  	void __iomem *base;
> @@ -391,6 +392,14 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
> +	if (IS_ERR(pwm->bus_clk)) {
> +		if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "get bus clock failed %pe\n",
> +				pwm->bus_clk);
> +		return PTR_ERR(pwm->bus_clk);
> +	}
> +
>  	pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
>  	if (IS_ERR(pwm->rst)) {
>  		if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> @@ -407,6 +416,17 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	/*
> +	 * We're keeping the bus clock on for the sake of simplicity.
> +	 * Actually it only needs to be on for hardware register accesses.
> +	 */
> +	ret = clk_prepare_enable(pwm->bus_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Cannot prepare and enable bus_clk %d\n",
> +			ret);

nitpick: other error messages in this driver start with a lower case
letter.

Until there is an equivalent for %pe that consumes an int, I suggest to
use

	dev_err(&pdev->dev, "Cannot prepare and enable bus_clk: %pe\n",
	        ERR_PTR(ret));

to benefit from a symbolic error name instead of an error constant.

Best regards
Uwe

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