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

[Jitao Shi <jitao.shi@mediatek.com>]

On Sun, 2021-06-06 at 23:22 +0200, Uwe Kleine-König wrote:
> 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@mediatek.com>
> > ---
> >  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.

I'll fix it next version.

Thanks for your review.
> 
> >  }
> >  
> > -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.
> 
I'll separate .get_state() next version.

Thanks for your review.

> >  {
> >  	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);

I'll fix it next version.


> 
> > +	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().
> 

I'll fix it next version.


> > +	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
> 

Thanks for your review.

Best Regards
Jitao


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