linux-kernel - Re: [PATCH v5 2/3] pwm: mtk_disp: implement atomic API .apply()

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Date:   Fri, 25 Jun 2021 19:52:19 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Jitao Shi <jitao.shi@...iatek.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        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 v5 2/3] pwm: mtk_disp: implement atomic API .apply()

On Wed, Jun 16, 2021 at 04:52:23PM +0800, Jitao Shi wrote:
> Switch the driver to support the .apply() method.
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> ---
>  drivers/pwm/pwm-mtk-disp.c | 69 ++++++++++----------------------------
>  1 file changed, 17 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> index 204d76beeb26..a4766e931b68 100644
> --- a/drivers/pwm/pwm-mtk-disp.c
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -67,14 +67,25 @@ 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_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			      const struct pwm_state *state)
>  {
>  	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
>  	u32 clk_div, period, high_width, value;
>  	u64 div, rate;
>  	int err;
>  

Here something like:

	if (state->polarity != PWM_POLARITY_NORMAL)
		return -EINVAL;

is missing.

> +	if (!state->enabled) {
> +		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
> +					 0x0);
> +		if (mdp->enabled) {
> +			clk_disable_unprepare(mdp->clk_mm);
> +			clk_disable_unprepare(mdp->clk_main);
> +		}
> +		mdp->enabled = false;
> +		return 0;
> +	}
> +
>  	if (!mdp->enabled) {
>  		err = clk_prepare_enable(mdp->clk_main);
>  		if (err < 0) {
> @@ -102,7 +113,7 @@ 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) >>

This multiplication might overflow. But maybe it's sensible to address
this in a separate commit to keep things simple.

>  			  PWM_PERIOD_BIT_WIDTH;
>  	if (clk_div > PWM_CLKDIV_MAX) {
>  		if (!mdp->enabled) {
> @@ -112,11 +123,11 @@ 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);

ditto.

Best regards
Uwe

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

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