linux-kernel - Re: [PATCH v2 2/7] pwm: sun4i: Add an optional probe for reset line

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Date:   Mon, 4 Nov 2019 09:11:57 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Philipp Zabel <p.zabel@...gutronix.de>
Subject: Re: [PATCH v2 2/7] pwm: sun4i: Add an optional probe for reset line

Hello,

adding Philipp Zabel (= reset controller maintainer) to Cc: and so I'm
not stripping the uncommented parts of the patch.

On Sun, Nov 03, 2019 at 09:33:29PM +0100, Clément Péron wrote:
> From: Jernej Skrabec <jernej.skrabec@...l.net>
> 
> H6 PWM core needs deasserted reset line 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 | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 6f5840a1a82d..d194b8ebdb00 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -16,6 +16,7 @@
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/pwm.h>
> +#include <linux/reset.h>
>  #include <linux/slab.h>
>  #include <linux/spinlock.h>
>  #include <linux/time.h>
> @@ -78,6 +79,7 @@ struct sun4i_pwm_data {
>  struct sun4i_pwm_chip {
>  	struct pwm_chip chip;
>  	struct clk *clk;
> +	struct reset_control *rst;
>  	void __iomem *base;
>  	spinlock_t ctrl_lock;
>  	const struct sun4i_pwm_data *data;
> @@ -365,6 +367,20 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>  	if (IS_ERR(pwm->clk))
>  		return PTR_ERR(pwm->clk);
>  
> +	pwm->rst = devm_reset_control_get_optional(&pdev->dev, NULL);
> +	if (IS_ERR(pwm->rst)) {
> +		if (PTR_ERR(pwm->rst) == -EPROBE_DEFER)
> +			return PTR_ERR(pwm->rst);
> +		dev_info(&pdev->dev, "no reset control found\n");

I would degrade this to a dev_dbg. Otherwise this spams the log for all
unaffected machines. devm_reset_control_get_optional() is defined in a
section that has a comment "These inline function calls will be removed
once all consumers have been moved over to the new explicit API.", so I
guess you want devm_reset_control_get_optional_exclusive or even
devm_reset_control_get_optional_shared here.

@Philipp: maybe a check in checkpatch that warns about introduction of
such new instances would be good?!

> +	}
> +
> +	/* Deassert reset */
> +	ret = reset_control_deassert(pwm->rst);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Cannot deassert reset control\n");
> +		return ret;
> +	}
> +
>  	pwm->chip.dev = &pdev->dev;
>  	pwm->chip.ops = &sun4i_pwm_ops;
>  	pwm->chip.base = -1;
> @@ -377,19 +393,31 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>  	ret = pwmchip_add(&pwm->chip);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
> -		return ret;
> +		goto err_pwm_add;
>  	}
>  
>  	platform_set_drvdata(pdev, pwm);
>  
>  	return 0;
> +
> +err_pwm_add:
> +	reset_control_assert(pwm->rst);
> +
> +	return ret;
>  }
>  
>  static int sun4i_pwm_remove(struct platform_device *pdev)
>  {
>  	struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);
> +	int ret;
> +
> +	ret = pwmchip_remove(&pwm->chip);
> +	if (ret)
> +		return ret;
> +
> +	reset_control_assert(pwm->rst);
>  
> -	return pwmchip_remove(&pwm->chip);
> +	return 0;
>  }
>  
>  static struct platform_driver sun4i_pwm_driver = {

Best regards
Uwe

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