linux-kernel - Re: [PATCH v4 1/3] pwm: mtk-disp: adjust the clocks to avoid them mismatch

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Date:   Sun, 6 Jun 2021 23:11:46 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Jitao Shi <jitao.shi@...iatek.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pwm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        srv_heupstream@...iatek.com, yingjoe.chen@...iatek.com,
        eddie.huang@...iatek.com, cawa.cheng@...iatek.com,
        bibby.hsieh@...iatek.com, ck.hu@...iatek.com, stonea168@....com,
        huijuan.xie@...iatek.com
Subject: Re: [PATCH v4 1/3] pwm: mtk-disp: adjust the clocks to avoid them
 mismatch

Hello,

you missed to address Lee and me for your patch series. I just happend
to stumble over this series by a fluke.

On Thu, Jun 03, 2021 at 06:05:29PM +0800, Jitao Shi wrote:
> The clk_main and clk_mm clocks are still on when system enter
> suspend. That will casue the power consumption.
> 
> The clocks call the clk_prepare() in probe(), but the clk_unprepare()
> is called in remove(), it isn't called when system suspend.

The English could be improved here. Something like:

	The clks "main" and "mm" are prepared in .probe() (and
	unprepared in .remove()). This results in the clocks being on
	during suspend which results in unnecessarily increased power
	consumption.

> Remove the clcok opterations from probe() and remove.

s/clcok/clock/, s/e\./e()/

> Add the clk_prepare_enable() in config().
> Add the clk_disable_unprepare() in disable().
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> ---
>  drivers/pwm/pwm-mtk-disp.c | 81 ++++++++++++++++----------------------
>  1 file changed, 33 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 9b3ba401a3db..b5771e2c54b8 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -47,6 +47,7 @@ struct mtk_disp_pwm {
>  	struct clk *clk_main;
>  	struct clk *clk_mm;
>  	void __iomem *base;
> +	bool enabled;
>  };
>  
>  static inline struct mtk_disp_pwm *to_mtk_disp_pwm(struct pwm_chip *chip)
> @@ -74,6 +75,22 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	u64 div, rate;
>  	int err;
>  
> +	if (!mdp->enabled) {
> +		err = clk_prepare_enable(mdp->clk_main);
> +		if (err < 0) {
> +			dev_err(chip->dev, "Can't enable mdp->clk_main: %d\n",
> +				err);
> +			return err;

Please use %pe to get symbolic error names which are better
understandable.

> +		}
> +		err = clk_prepare_enable(mdp->clk_mm);
> +		if (err < 0) {
> +			dev_err(chip->dev, "Can't enable mdp->clk_mm: %d\n",
> +				err);
> +			clk_disable_unprepare(mdp->clk_main);
> +			return err;
> +		}
> +	}
> +
>  	/*
>  	 * Find period, high_width and clk_div to suit duty_ns and period_ns.
>  	 * Calculate proper div value to keep period value in the bound.
> @@ -87,9 +104,15 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	rate = clk_get_rate(mdp->clk_main);
>  	clk_div = div_u64(rate * period_ns, NSEC_PER_SEC) >>
>  			  PWM_PERIOD_BIT_WIDTH;
> -	if (clk_div > PWM_CLKDIV_MAX)
> +	if (clk_div > PWM_CLKDIV_MAX) {
> +		dev_err(chip->dev, "clock rate is too high: rate = %d Hz\n",
> +			rate);

Adding an error message here is orthogonal to this patch. Either drop it
or mention it in the commit log please.

> +		if (!mdp->enabled) {
> +			clk_disable_unprepare(mdp->clk_mm);
> +			clk_disable_unprepare(mdp->clk_main);
> +		}
>  		return -EINVAL;
> -
> +	}
>  	div = NSEC_PER_SEC * (clk_div + 1);
>  	period = div64_u64(rate * period_ns, div);
>  	if (period > 0)
> [...]
> @@ -135,18 +145,9 @@ static int mtk_disp_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>  	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
>  	int err;
>  
> -	err = clk_enable(mdp->clk_main);
> -	if (err < 0)
> -		return err;
> -
> -	err = clk_enable(mdp->clk_mm);
> -	if (err < 0) {
> -		clk_disable(mdp->clk_main);
> -		return err;
> -	}
> -
>  	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
>  				 mdp->data->enable_mask);
> +	mdp->enabled = true;

The modification to .enable() looks wrong. After the PWM was disabled
the clocks are off, so .enable() must reenable them, doesn't it?

>  	return 0;
>  }

Best regards
Uwe

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

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