Re: [PATCH v5 1/3] pwm: mtk-disp: adjust the clocks to avoid them mismatch

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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On Wed, Jun 16, 2021 at 04:52:22PM +0800, Jitao Shi wrote:
> 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 clock operations from .probe() and .remove().
> Add the clk_prepare_enable() in .config().
> Add the clk_disable_unprepare() in .disable().
> Remove the MT2701 double buffer comment.
> 
> Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> ---
>  drivers/pwm/pwm-mtk-disp.c | 116 ++++++++++++++++++-------------------
>  1 file changed, 57 insertions(+), 59 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 9b3ba401a3db..204d76beeb26 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: %pe\n",
> +				ERR_PTR(err));
> +			return err;
> +		}
> +		err = clk_prepare_enable(mdp->clk_mm);
> +		if (err < 0) {
> +			dev_err(chip->dev, "Can't enable mdp->clk_mm: %pe\n",
> +				ERR_PTR(err));
> +			clk_disable_unprepare(mdp->clk_main);
> +			return err;
> +		}
> +	}
> +

The logic becomes a tad simpler if you prepare_enable unconditionally on
entry and disable_unprepare on exit. Given that in the mdp->enabled ==
true the clocks are already on they are a noop in this case and the
matching disable just decreases the usage count.

>  	/*
>  	 * 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 +104,13 @@ 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) {
> +		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)
> @@ -98,16 +119,6 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	high_width = div64_u64(rate * duty_ns, div);
>  	value = period | (high_width << PWM_HIGH_WIDTH_SHIFT);
>  
> -	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, mdp->data->con0,
>  				 PWM_CLKDIV_MASK,
>  				 clk_div << PWM_CLKDIV_SHIFT);
> @@ -122,10 +133,19 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  		mtk_disp_pwm_update_bits(mdp, mdp->data->commit,
>  					 mdp->data->commit_mask,
>  					 0x0);
> +	} else {
> +		mtk_disp_pwm_update_bits(mdp, mdp->data->bls_debug,
> +					 mdp->data->bls_debug_mask,
> +					 mdp->data->bls_debug_mask);
> +		mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
> +					 mdp->data->con0_sel,
> +					 mdp->data->con0_sel);

This is unrelated for this patch, isn't it?

>  	}
>  
> -	clk_disable(mdp->clk_mm);
> -	clk_disable(mdp->clk_main);
> +	if (!mdp->enabled) {
> +		clk_disable_unprepare(mdp->clk_mm);
> +		clk_disable_unprepare(mdp->clk_main);
> +	}
>  
>  	return 0;
>  }
> @@ -135,18 +155,25 @@ 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;
> +	if (!mdp->enabled) {
> +		err = clk_prepare_enable(mdp->clk_main);
> +		if (err < 0) {
> +			dev_err(chip->dev, "Can't enable mdp->clk_main: %pe\n",
> +				ERR_PTR(err));
> +			return err;
> +		}
> +		err = clk_prepare_enable(mdp->clk_mm);
> +		if (err < 0) {
> +			dev_err(chip->dev, "Can't enable mdp->clk_mm: %pe\n",
> +				ERR_PTR(err));
> +			clk_disable_unprepare(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;
>  
>  	return 0;
>  }
> @@ -158,8 +185,11 @@ static void mtk_disp_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>  	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
>  				 0x0);
>  
> -	clk_disable(mdp->clk_mm);
> -	clk_disable(mdp->clk_main);
> +	if (mdp->enabled) {
> +		clk_disable_unprepare(mdp->clk_mm);
> +		clk_disable_unprepare(mdp->clk_main);
> +	}
> +	mdp->enabled = false;
>  }
>  
>  static const struct pwm_ops mtk_disp_pwm_ops = {
> @@ -192,58 +222,26 @@ static int mtk_disp_pwm_probe(struct platform_device *pdev)
>  	if (IS_ERR(mdp->clk_mm))
>  		return PTR_ERR(mdp->clk_mm);
>  
> -	ret = clk_prepare(mdp->clk_main);
> -	if (ret < 0)
> -		return ret;
> -
> -	ret = clk_prepare(mdp->clk_mm);
> -	if (ret < 0)
> -		goto disable_clk_main;
> -
>  	mdp->chip.dev = &pdev->dev;
>  	mdp->chip.ops = &mtk_disp_pwm_ops;
>  	mdp->chip.npwm = 1;
>  
>  	ret = pwmchip_add(&mdp->chip);
>  	if (ret < 0) {
> -		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> -		goto disable_clk_mm;
> +		dev_err(&pdev->dev, "pwmchip_add() failed: %pe\n", ERR_PTR(ret));
> +		return ret;
>  	}
>  
>  	platform_set_drvdata(pdev, mdp);
>  
> -	/*
> -	 * For MT2701, disable double buffer before writing register
> -	 * and select manual mode and use PWM_PERIOD/PWM_HIGH_WIDTH.
> -	 */
> -	if (!mdp->data->has_commit) {
> -		mtk_disp_pwm_update_bits(mdp, mdp->data->bls_debug,
> -					 mdp->data->bls_debug_mask,
> -					 mdp->data->bls_debug_mask);
> -		mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
> -					 mdp->data->con0_sel,
> -					 mdp->data->con0_sel);
> -	}
> -

Similar than above this is unrelated at least to what you described in
the commit log. Maybe this part is better split into a separate patch?


>  	return 0;
> -
> -disable_clk_mm:
> -	clk_unprepare(mdp->clk_mm);
> -disable_clk_main:
> -	clk_unprepare(mdp->clk_main);
> -	return ret;
>  }

Best regards
Uwe

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

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