Re: [PATCH v4 3/3] pwm: mtk-disp: Switch to atomic API

[Uwe Kleine-König]

Hello,

On Thu, Jun 03, 2021 at 06:05:31PM +0800, Jitao Shi wrote:
> Convert the legacy api to atomic API.
> 
> Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
> ---
>  drivers/pwm/pwm-mtk-disp.c | 78 ++++++++++++++++++++++++++++----------
>  1 file changed, 59 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index b87b3c00a685..d77348d0527c 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -67,8 +67,8 @@ static void mtk_disp_pwm_update_bits(struct mtk_disp_pwm *mdp, u32 offset,
>  	writel(value, address);
>  }
>  
> -static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> -			       int duty_ns, int period_ns)
> +static int mtk_disp_pwm_config(struct pwm_chip *chip,
> +			       const struct pwm_state *state)
>  {
>  	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
>  	u32 clk_div, period, high_width, value;
> @@ -102,7 +102,7 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	 * high_width = (PWM_CLK_RATE * duty_ns) / (10^9 * (clk_div + 1))
>  	 */
>  	rate = clk_get_rate(mdp->clk_main);
> -	clk_div = div_u64(rate * period_ns, NSEC_PER_SEC) >>
> +	clk_div = div_u64(rate * state->period, NSEC_PER_SEC) >>
>  			  PWM_PERIOD_BIT_WIDTH;
>  	if (clk_div > PWM_CLKDIV_MAX) {
>  		dev_err(chip->dev, "clock rate is too high: rate = %d Hz\n",
> @@ -114,11 +114,11 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  		return -EINVAL;
>  	}
>  	div = NSEC_PER_SEC * (clk_div + 1);
> -	period = div64_u64(rate * period_ns, div);
> +	period = div64_u64(rate * state->period, div);
>  	if (period > 0)
>  		period--;
>  
> -	high_width = div64_u64(rate * duty_ns, div);
> +	high_width = div64_u64(rate * state->duty_cycle, div);
>  	value = period | (high_width << PWM_HIGH_WIDTH_SHIFT);
>  
>  	mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
> @@ -144,39 +144,79 @@ static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  					 mdp->data->con0_sel);
>  	}
>  
> +	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> +				 mdp->data->enable_mask);
> +	mdp->enabled = true;
> +
>  	return 0;
>  }
>  
> -static int mtk_disp_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			      const struct pwm_state *state)
>  {
>  	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
> -	int err;
>  
> -	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> -				 mdp->data->enable_mask);
> -	mdp->enabled = true;
> +	if (!state->enabled) {
> +		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> +					 0x0);
>  
> -	return 0;
> +		if (mdp->enabled) {
> +			clk_disable_unprepare(mdp->clk_mm);
> +			clk_disable_unprepare(mdp->clk_main);
> +		}
> +		mdp->enabled = false;
> +		return 0;
> +	}
> +
> +	return mtk_disp_pwm_config(chip, state);

Please unroll this function call. Having the old name is irritating.

>  }
>  
> -static void mtk_disp_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +static void mtk_disp_pwm_get_state(struct pwm_chip *chip,
> +				   struct pwm_device *pwm,
> +				   struct pwm_state *state)

Adding .get_state() is great and warrants a separate patch.

>  {
>  	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
> +	u32 clk_div, period, high_width, con0, con1;
> +	u64 rate;
> +	int err;
>  
> -	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> -				 0x0);
> +	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 = 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;
> +		}
> +	}
> +
> +	rate = clk_get_rate(mdp->clk_main);
>  
> -	if (mdp->enabled) {
> +	con0 = readl(mdp->base + mdp->data->con0);
> +	con1 = readl(mdp->base + mdp->data->con1);
> +
> +	state->enabled = !!(con0 & BIT(0));
> +
> +	clk_div = (con0 & PWM_CLKDIV_MASK) >> PWM_CLKDIV_SHIFT;

clk_div = FIELD_GET(PWM_CLKDIV_MASK, con0);

> +	period = con1 & PWM_PERIOD_MASK;
> +	state->period = div_u64(period * (clk_div + 1) * NSEC_PER_SEC, rate);

Can this multiplication overflow? Note this is a 32bit multiplication
only. As .apply() uses round-down in the divisions (which is good)
please round up there to get idempotency between .get_state() and
.apply().

> +	high_width = (con1 & PWM_HIGH_WIDTH_MASK) >> PWM_HIGH_WIDTH_SHIFT;
> +	state->duty_cycle = div_u64(high_width * (clk_div + 1) * NSEC_PER_SEC,
> +				    rate);
> +
> +	if (!mdp->enabled) {
>  		clk_disable_unprepare(mdp->clk_mm);
>  		clk_disable_unprepare(mdp->clk_main);
>  	}
> -	mdp->enabled = false;
>  }

If my review comments contain too little details for you to understand,
please feel free to ask. I'm willing to explain in more detail.

Best regards
Uwe

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

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