linux-kernel - Re: [PATCH 1/2] rtc: rtc-twl: Use devm

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Date:	Fri, 06 Dec 2013 10:49:04 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Grygorii Strashko' <grygorii.strashko@...com>,
	'Andrew Morton' <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	'Alessandro Zummo' <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, 'Kevin Hilman' <khilman@...aro.org>,
	'Tony Lindgren' <tony@...mide.com>,
	'Peter Ujfalusi' <peter.ujfalusi@...com>,
	'Jingoo Han' <jg1.han@...sung.com>
Subject: Re: [PATCH 1/2] rtc: rtc-twl: Use devm_*() functions

On Friday, December 06, 2013 1:51 AM, Grygorii Strashko wrote:
> On 12/05/2013 03:03 AM, Jingoo Han wrote:
> > Use devm_*() functions to make cleanup paths simpler, and remove
> > unnecessary remove().
> >
> > Signed-off-by: Jingoo Han <jg1.han@...sung.com>
> > ---
> >   drivers/rtc/rtc-twl.c |   38 +++++++++++++-------------------------
> >   1 file changed, 13 insertions(+), 25 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-twl.c b/drivers/rtc/rtc-twl.c
> > index c2e80d7..1915464 100644
> > --- a/drivers/rtc/rtc-twl.c
> > +++ b/drivers/rtc/rtc-twl.c
> > @@ -479,7 +479,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
> >   	u8 rd_reg;
> >
> >   	if (irq <= 0)
> > -		goto out1;
> > +		return ret;
> >
> >   	/* Initialize the register map */
> >   	if (twl_class_is_4030())
> > @@ -489,7 +489,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
> >
> >   	ret = twl_rtc_read_u8(&rd_reg, REG_RTC_STATUS_REG);
> >   	if (ret < 0)
> > -		goto out1;
> > +		return ret;
> >
> >   	if (rd_reg & BIT_RTC_STATUS_REG_POWER_UP_M)
> >   		dev_warn(&pdev->dev, "Power up reset detected.\n");
> > @@ -500,7 +500,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
> >   	/* Clear RTC Power up reset and pending alarm interrupts */
> >   	ret = twl_rtc_write_u8(rd_reg, REG_RTC_STATUS_REG);
> >   	if (ret < 0)
> > -		goto out1;
> > +		return ret;
> >
> >   	if (twl_class_is_6030()) {
> >   		twl6030_interrupt_unmask(TWL6030_RTC_INT_MASK,
> > @@ -512,7 +512,7 @@ static int twl_rtc_probe(struct platform_device *pdev)
> >   	dev_info(&pdev->dev, "Enabling TWL-RTC\n");
> >   	ret = twl_rtc_write_u8(BIT_RTC_CTRL_REG_STOP_RTC_M, REG_RTC_CTRL_REG);
> >   	if (ret < 0)
> > -		goto out1;
> > +		return ret;
> >
> >   	/* ensure interrupts are disabled, bootloaders can be strange */
> >   	ret = twl_rtc_write_u8(0, REG_RTC_INTERRUPTS_REG);
> > @@ -522,34 +522,29 @@ static int twl_rtc_probe(struct platform_device *pdev)
> >   	/* init cached IRQ enable bits */
> >   	ret = twl_rtc_read_u8(&rtc_irq_bits, REG_RTC_INTERRUPTS_REG);
> >   	if (ret < 0)
> > -		goto out1;
> > +		return ret;
> >
> >   	device_init_wakeup(&pdev->dev, 1);
> >
> > -	rtc = rtc_device_register(pdev->name,
> > -				  &pdev->dev, &twl_rtc_ops, THIS_MODULE);
> > +	rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
> > +					&twl_rtc_ops, THIS_MODULE);
> >   	if (IS_ERR(rtc)) {
> > -		ret = PTR_ERR(rtc);
> >   		dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
> >   			PTR_ERR(rtc));
> > -		goto out1;
> > +		return PTR_ERR(rtc);
> >   	}
> >
> > -	ret = request_threaded_irq(irq, NULL, twl_rtc_interrupt,
> > -				   IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> > -				   dev_name(&rtc->dev), rtc);
> > +	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> > +					twl_rtc_interrupt,
> > +					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> > +					dev_name(&rtc->dev), rtc);
> 
> Looks like this will change driver release order and free_irq
> will be called after RTC device is unregistered.
> I think, you need to request irq first -> then register RTC device.
> Right?

Hi Grygorii Strashko,

No, free_irq() will be called before RTC device is unregistered.

In probe(), the following functions are called as below:
  1. devm_rtc_device_register() -> rtc_device_register()
  2. devm_request_threaded_irq() -> request_threaded_irq()

The release functions will be inversely called.
When removing rtc-twl.
  1. devm_irq_release() -> free_irq()
  2. devm_rtc_device_release() -> rtc_device_unregister()

Thus, it is safe.
Thank you for your feedback. :-)

Best regards,
Jingoo Han

> 
> >   	if (ret < 0) {
> >   		dev_err(&pdev->dev, "IRQ is not free.\n");
> > -		goto out2;
> > +		return ret;
> >   	}
> >
> >   	platform_set_drvdata(pdev, rtc);
> >   	return 0;
> > -
> > -out2:
> > -	rtc_device_unregister(rtc);
> > -out1:
> > -	return ret;
> >   }
> >
> >   /*
> > @@ -559,9 +554,6 @@ out1:
> >   static int twl_rtc_remove(struct platform_device *pdev)
> >   {
> >   	/* leave rtc running, but disable irqs */
> > -	struct rtc_device *rtc = platform_get_drvdata(pdev);
> > -	int irq = platform_get_irq(pdev, 0);
> > -
> >   	mask_rtc_irq_bit(BIT_RTC_INTERRUPTS_REG_IT_ALARM_M);
> >   	mask_rtc_irq_bit(BIT_RTC_INTERRUPTS_REG_IT_TIMER_M);
> >   	if (twl_class_is_6030()) {
> > @@ -571,10 +563,6 @@ static int twl_rtc_remove(struct platform_device *pdev)
> >   			REG_INT_MSK_STS_A);
> >   	}
> >
> > -
> > -	free_irq(irq, rtc);
> > -
> > -	rtc_device_unregister(rtc);
> >   	return 0;
> >   }
> >
> >

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