linux-kernel - Re: [PATCH] pwm: berlin: Add PM support

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Message-ID: <20151125163019.64e80799@xhacker>
Date:	Wed, 25 Nov 2015 16:30:19 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Thierry Reding <thierry.reding@...il.com>,
	<sebastian.hesselbarth@...il.com>,
	<antoine.tenart@...e-electrons.com>
CC:	<linux-pwm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] pwm: berlin: Add PM support

Dear Thierry,

On Tue, 24 Nov 2015 17:23:06 +0100
Thierry Reding wrote:

> On Tue, Nov 24, 2015 at 01:43:05PM +0800, Jisheng Zhang wrote:
> > This patch adds S2R support for berlin pwm driver.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
> >  drivers/pwm/pwm-berlin.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 56 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pwm/pwm-berlin.c b/drivers/pwm/pwm-berlin.c
> > index 6510812..2afdb40 100644
> > --- a/drivers/pwm/pwm-berlin.c
> > +++ b/drivers/pwm/pwm-berlin.c
> > @@ -27,10 +27,20 @@
> >  #define BERLIN_PWM_TCNT			0xc
> >  #define  BERLIN_PWM_MAX_TCNT		65535
> >  
> > +#define NUM_PWM_CHANNEL			4	/* berlin PWM channels */
> > +
> > +struct berlin_pwm_context {
> > +	u32	enable;
> > +	u32	ctrl;
> > +	u32	duty;
> > +	u32	tcnt;
> > +};
> > +
> >  struct berlin_pwm_chip {
> >  	struct pwm_chip chip;
> >  	struct clk *clk;
> >  	void __iomem *base;
> > +	struct berlin_pwm_context ctx[NUM_PWM_CHANNEL];  
> 
> Please don't do this. You can easily attach per-PWM data using the
> pwm_set_chip_data() function and retrieve it using pwm_get_chip_data().

Got it. Will do in v2.

> 
> >  };
> >  
> >  static inline struct berlin_pwm_chip *to_berlin_pwm_chip(struct pwm_chip *chip)
> > @@ -176,7 +186,7 @@ static int berlin_pwm_probe(struct platform_device *pdev)
> >  	pwm->chip.dev = &pdev->dev;
> >  	pwm->chip.ops = &berlin_pwm_ops;
> >  	pwm->chip.base = -1;
> > -	pwm->chip.npwm = 4;
> > +	pwm->chip.npwm = NUM_PWM_CHANNEL;
> >  	pwm->chip.can_sleep = true;
> >  	pwm->chip.of_xlate = of_pwm_xlate_with_flags;
> >  	pwm->chip.of_pwm_n_cells = 3;
> > @@ -204,12 +214,57 @@ static int berlin_pwm_remove(struct platform_device *pdev)
> >  	return ret;
> >  }
> >  
> > +#ifdef CONFIG_PM_SLEEP
> > +static int berlin_pwm_suspend(struct device *dev)
> > +{
> > +	int i;  
> 
> unsigned int, please.

will do in v2. 

> 
> > +	struct berlin_pwm_chip *pwm = dev_get_drvdata(dev);
> > +
> > +	for (i = 0; i < pwm->chip.npwm; i++) {
> > +		struct berlin_pwm_context *ctx = &pwm->ctx[i];
> > +
> > +		ctx->enable = berlin_pwm_readl(pwm, i, BERLIN_PWM_ENABLE);
> > +		ctx->ctrl = berlin_pwm_readl(pwm, i, BERLIN_PWM_CONTROL);
> > +		ctx->duty = berlin_pwm_readl(pwm, i, BERLIN_PWM_DUTY);
> > +		ctx->tcnt = berlin_pwm_readl(pwm, i, BERLIN_PWM_TCNT);
> > +	}
> > +	clk_disable_unprepare(pwm->clk);
> > +
> > +	return 0;
> > +}
> > +
> > +static int berlin_pwm_resume(struct device *dev)
> > +{
> > +	int i;  
> 
> unsigned int, please.

will do

> 
> > +	struct berlin_pwm_chip *pwm = dev_get_drvdata(dev);
> > +
> > +	clk_prepare_enable(pwm->clk);  
> 
> Always check the return value of this function.

oops, thanks for pointing out this. Will do in v2.

> 
> > +	for (i = 0; i < pwm->chip.npwm; i++) {
> > +		struct berlin_pwm_context *ctx = &pwm->ctx[i];
> > +
> > +		berlin_pwm_writel(pwm, i, ctx->ctrl, BERLIN_PWM_CONTROL);
> > +		berlin_pwm_writel(pwm, i, ctx->duty, BERLIN_PWM_DUTY);
> > +		berlin_pwm_writel(pwm, i, ctx->tcnt, BERLIN_PWM_TCNT);
> > +		berlin_pwm_writel(pwm, i, ctx->enable, BERLIN_PWM_ENABLE);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static SIMPLE_DEV_PM_OPS(berlin_pwm_pm_ops, berlin_pwm_suspend,
> > +			 berlin_pwm_resume);
> > +#define BERLIN_PWM_PM_OPS	(&berlin_pwm_pm_ops)
> > +#else
> > +#define BERLIN_PWM_PM_OPS	NULL
> > +#endif  
> 
> This is a weird way of writing this. I think a more typical way would be
> to have the #ifdef contain only the implementation and then define the
> dev_pm_ops variable unconditonally, so you don't need a separate macro
> for it.
> 

The reason why I introduced one more macro is: struct dev_pm_ops contains
23 pointers now, if there's no BERLIN_PWM_PM_OPS macro, there will be always a
dev_pm_ops even if PM_SLEEP isn't enabled. I dunno whether there's any
elegant solution for this case.

How about define SIMPLE_DEV_PM_OPS as NULL if PM_SLEEP isn't enabled?

Thanks,
Jisheng

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