linux-kernel - Re: [PATCH v2 03/10] pwm: imx: Rewrite imx_pwm_*_v1 code to facilitate switch to atomic pwm operation

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Date:   Thu, 27 Oct 2016 10:22:18 +0200
From:   Lukasz Majewski <l.majewski@...ess.pl>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Stefan Agner <stefan@...er.ch>, 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 v2 03/10] pwm: imx: Rewrite imx_pwm_*_v1 code to
 facilitate switch to atomic pwm operation

Hi Boris,

> On Thu, 27 Oct 2016 08:29:39 +0200
> Lukasz Majewski <l.majewski@...ess.pl> wrote:
> 
> > The code has been rewritten to remove "generic" calls to
> > imx_pwm_{enable|disable|config}.
> > 
> > Such approach would facilitate switch to atomic PWM (a.k.a
> > ->apply()) implementation.
> > 
> > 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>
> > ---
> > Changes for v2:
> > - Add missing clock unprepare for clk_ipg
> > - Enable peripheral PWM clock (clk_per)
> > ---
> >  drivers/pwm/pwm-imx.c | 50
> > ++++++++++++++++++++++++++++++++++++++------------ 1 file changed,
> > 38 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> > index ea3ce79..822eb5a 100644
> > --- a/drivers/pwm/pwm-imx.c
> > +++ b/drivers/pwm/pwm-imx.c
> > @@ -65,8 +65,6 @@ struct imx_chip {
> >  static int imx_pwm_config_v1(struct pwm_chip *chip,
> >  		struct pwm_device *pwm, int duty_ns, int period_ns)
> >  {
> > -	struct imx_chip *imx = to_imx_chip(chip);
> > -
> >  	/*
> >  	 * The PWM subsystem allows for exact frequencies. However,
> >  	 * I cannot connect a scope on my device to the PWM line
> > and @@ -84,26 +82,56 @@ static int imx_pwm_config_v1(struct
> > pwm_chip *chip,
> >  	 * both the prescaler (/1 .. /128) and then by CLKSEL
> >  	 * (/2 .. /16).
> >  	 */
> > +	struct imx_chip *imx = to_imx_chip(chip);
> >  	u32 max = readl(imx->mmio_base + MX1_PWMP);
> >  	u32 p = max * duty_ns / period_ns;
> > +	int ret;
> > +
> > +	ret = clk_prepare_enable(imx->clk_ipg);
> > +	if (ret)
> > +		return ret;
> > +
> >  	writel(max - p, imx->mmio_base + MX1_PWMS);
> >  
> > +	clk_disable_unprepare(imx->clk_ipg);
> > +
> >  	return 0;
> >  }
> >  
> > -static void imx_pwm_set_enable_v1(struct pwm_chip *chip, bool
> > enable) +static int imx_pwm_enable_v1(struct pwm_chip *chip, struct
> > pwm_device *pwm) {
> >  	struct imx_chip *imx = to_imx_chip(chip);
> > +	int ret;
> >  	u32 val;
> >  
> > +	ret = clk_prepare_enable(imx->clk_ipg);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = clk_prepare_enable(imx->clk_per);
> > +	if (ret)
> > +		return ret;
> > +
> >  	val = readl(imx->mmio_base + MX1_PWMC);
> > +	val |= MX1_PWMC_EN;
> > +	writel(val, imx->mmio_base + MX1_PWMC);
> >  
> > -	if (enable)
> > -		val |= MX1_PWMC_EN;
> > -	else
> > -		val &= ~MX1_PWMC_EN;
> > +	clk_disable_unprepare(imx->clk_ipg);
> > +
> > +	return 0;
> > +}
> > +
> > +static void imx_pwm_disable_v1(struct pwm_chip *chip, struct
> > pwm_device *pwm) +{
> > +	struct imx_chip *imx = to_imx_chip(chip);
> > +	u32 val;
> > +
> > +	val = readl(imx->mmio_base + MX1_PWMC);
> > +	val &= ~MX1_PWMC_EN;
> >  
> >  	writel(val, imx->mmio_base + MX1_PWMC);
> 
> Are you sure you don't need to enable the ipg clk when manipulating
> the PWMC register?
> If it's not needed here, then it's probably not needed in
> imx_pwm_enable_v1() either.

Yes, probably it is needed.

As I've mentioned in the cover letter - I do not have PWMv1 HW so I can
only compile test the code.

(And here support from the community is very welcome).

Best regards,
Łukasz Majewski

> 
> > +
> > +	clk_disable_unprepare(imx->clk_per);
> >  }
> >  
> >  static int imx_pwm_config_v2(struct pwm_chip *chip,
> > @@ -241,9 +269,9 @@ static void imx_pwm_disable(struct pwm_chip
> > *chip, struct pwm_device *pwm) }
> >  
> >  static struct pwm_ops imx_pwm_ops_v1 = {
> > -	.enable = imx_pwm_enable,
> > -	.disable = imx_pwm_disable,
> > -	.config = imx_pwm_config,
> > +	.enable = imx_pwm_enable_v1,
> > +	.disable = imx_pwm_disable_v1,
> > +	.config = imx_pwm_config_v1,
> >  	.owner = THIS_MODULE,
> >  };
> >  
> > @@ -262,8 +290,6 @@ struct imx_pwm_data {
> >  };
> >  
> >  static struct imx_pwm_data imx_pwm_data_v1 = {
> > -	.config = imx_pwm_config_v1,
> > -	.set_enable = imx_pwm_set_enable_v1,
> >  	.pwm_ops = &imx_pwm_ops_v1,
> >  };
> >  
> 


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