linux-kernel - Re: [PATCH v3 07/11] pwm: imx: Provide atomic PWM support for i.MX PWMv2

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Date:   Tue, 22 Nov 2016 13:55:33 -0800
From:   Stefan Agner <stefan@...er.ch>
To:     Lukasz Majewski <l.majewski@...ess.pl>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Fabio Estevam <fabio.estevam@....com>,
        Fabio Estevam <festevam@...il.com>,
        Lothar Wassmann <LW@...o-electronics.de>,
        Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>,
        kernel@...gutronix.de
Subject: Re: [PATCH v3 07/11] pwm: imx: Provide atomic PWM support for i.MX
 PWMv2

On 2016-11-01 00:10, Lukasz Majewski wrote:
> This commit provides apply() callback implementation for i.MX's PWMv2.
> 
> Suggested-by: Stefan Agner <stefan@...er.ch>
> Suggested-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> Signed-off-by: Lukasz Majewski <l.majewski@...ess.pl>
> Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> ---
> Changes for v3:
> - Remove ipg clock enable/disable functions
> 
> Changes for v2:
> - None
> ---
>  drivers/pwm/pwm-imx.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
> 
> diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> index ebe9b0c..cd53c05 100644
> --- a/drivers/pwm/pwm-imx.c
> +++ b/drivers/pwm/pwm-imx.c
> @@ -159,6 +159,75 @@ static void imx_pwm_wait_fifo_slot(struct pwm_chip *chip,
>  	}
>  }
>  
> +static int imx_pwm_apply_v2(struct pwm_chip *chip, struct pwm_device *pwm,
> +			    struct pwm_state *state)
> +{
> +	unsigned long period_cycles, duty_cycles, prescale;
> +	struct imx_chip *imx = to_imx_chip(chip);
> +	struct pwm_state cstate;
> +	unsigned long long c;
> +	u32 cr = 0;
> +	int ret;
> +
> +	pwm_get_state(pwm, &cstate);
> +

Couldn't we do:

if (cstate.enabled) { ...

> +	c = clk_get_rate(imx->clk_per);
> +	c *= state->period;
> +
> +	do_div(c, 1000000000);
> +	period_cycles = c;
> +
> +	prescale = period_cycles / 0x10000 + 1;
> +
> +	period_cycles /= prescale;
> +	c = (unsigned long long)period_cycles * state->duty_cycle;
> +	do_div(c, state->period);
> +	duty_cycles = c;
> +
> +	/*
> +	 * according to imx pwm RM, the real period value should be
> +	 * PERIOD value in PWMPR plus 2.
> +	 */
> +	if (period_cycles > 2)
> +		period_cycles -= 2;
> +	else
> +		period_cycles = 0;
> +
> +	/* Enable the clock if the PWM is being enabled. */
> +	if (state->enabled && !cstate.enabled) {
> +		ret = clk_prepare_enable(imx->clk_per);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/*
> +	 * Wait for a free FIFO slot if the PWM is already enabled, and flush
> +	 * the FIFO if the PWM was disabled and is about to be enabled.
> +	 */
> +	if (cstate.enabled)
> +		imx_pwm_wait_fifo_slot(chip, pwm);
> +	else if (state->enabled)
> +		imx_pwm_sw_reset(chip);
> +
> +	writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
> +	writel(period_cycles, imx->mmio_base + MX3_PWMPR);
> +
> +	cr |= MX3_PWMCR_PRESCALER(prescale) |
> +	      MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
> +	      MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH;
> +
> +	if (state->enabled)
> +		cr |= MX3_PWMCR_EN;

} else if (state->enabled) {
	imx_pwm_sw_reset(chip);
}

and get rid of the if (state->enabled) in between? This would safe us
useless recalculation when disabling the controller...

--
Stefan

> +
> +	writel(cr, imx->mmio_base + MX3_PWMCR);
> +
> +	/* Disable the clock if the PWM is being disabled. */
> +	if (!state->enabled && cstate.enabled)
> +		clk_disable_unprepare(imx->clk_per);
> +
> +	return 0;
> +}
> +
>  static int imx_pwm_config_v2(struct pwm_chip *chip,
>  		struct pwm_device *pwm, int duty_ns, int period_ns)
>  {
> @@ -273,6 +342,7 @@ static struct pwm_ops imx_pwm_ops_v2 = {
>  	.enable = imx_pwm_enable,
>  	.disable = imx_pwm_disable,
>  	.config = imx_pwm_config,
> +	.apply = imx_pwm_apply_v2,
>  	.owner = THIS_MODULE,
>  };