linux-kernel - RE: [PATCH] rtc: tps65910: Add RTC driver for TPS65910 PMIC RTC

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Date:	Mon, 30 Jul 2012 15:37:18 +0530
From:	Venu Byravarasu <vbyravarasu@...dia.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	"a.zummo@...ertech.it" <a.zummo@...ertech.it>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"kyle.manna@...l7.com" <kyle.manna@...l7.com>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] rtc: tps65910: Add RTC driver for TPS65910 PMIC RTC

Thanks Stephen for your comments.
Plz see my comments inline.


> -----Original Message-----
> From: Stephen Boyd [mailto:sboyd@...eaurora.org]
> Sent: Monday, July 30, 2012 2:47 PM
> To: Venu Byravarasu
> Cc: a.zummo@...ertech.it; sameo@...ux.intel.com;
> broonie@...nsource.wolfsonmicro.com; Laxman Dewangan;
> kyle.manna@...l7.com; rtc-linux@...glegroups.com; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH] rtc: tps65910: Add RTC driver for TPS65910 PMIC RTC
> 
> On 7/25/2012 11:35 PM, Venu Byravarasu wrote:
> > +
> > +static struct rtc_class_ops tps65910_rtc_ops = {
> 
> const?

Will add it in my next patch. 

> 
> > +	.read_time	= tps65910_rtc_read_time,
> > +	.set_time	= tps65910_rtc_set_time,
> > +	.read_alarm	= tps65910_rtc_read_alarm,
> > +	.set_alarm	= tps65910_rtc_set_alarm,
> > +	.alarm_irq_enable = tps65910_rtc_alarm_irq_enable,
> > +};
> > +
> > +static int __devinit tps65910_rtc_probe(struct platform_device *pdev)
> > +{
> > +	struct tps65910 *tps65910 = NULL;
> > +	struct tps65910_rtc *tps_rtc = NULL;
> > +	struct tps65910_board *pmic_plat_data;
> > +	int ret = -EINVAL;
> > +	int irq = 0;
> > +	u32 rtc_reg;
> 
> It seems like all the above assignments are useless as they're
> overwritten later in this function. Can you remove the assignments?
> 

Some of the non-intelligent compilers/tools complain as variables 
may get used uninitialized. Hence to avoid such complaints, initialized
them to some default values.
What harm do you see if I have local variables initialized during their declaration?

> > +
> > +	tps65910 = dev_get_drvdata(pdev->dev.parent);
> > +
> > +	tps_rtc = devm_kzalloc(&pdev->dev, sizeof(struct tps65910_rtc),
> > +			GFP_KERNEL);
> > +	if (!tps_rtc)
> > +		return -ENOMEM;
> > +
> > +	/* Clear pending interrupts */
> > +	ret = regmap_read(tps65910->regmap, TPS65910_RTC_STATUS,
> &rtc_reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret = regmap_write(tps65910->regmap, TPS65910_RTC_STATUS,
> rtc_reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	dev_dbg(&pdev->dev, "Enabling tps65910-RTC.\n");
> 
> Hmph, looks more like stopping the RTC.
> 

No, the register is a misnomer here.
As per data sheet of TPS65910, setting this bit will start RTC, 
instead of stopping as its name suggests.
 

> > +	rtc_reg = TPS65910_RTC_CTRL_STOP_RTC;
> > +	ret = regmap_write(tps65910->regmap, TPS65910_RTC_CTRL,
> rtc_reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	pmic_plat_data = dev_get_platdata(tps65910->dev);
> > +	irq = pmic_plat_data->irq_base;
> > +	if (irq <= 0) {
> > +		dev_warn(&pdev->dev, "Wake up is not possible as irq =
> %d\n",
> > +			irq);
> > +		return ret;
> > +	}
> > +
> > +	irq += TPS65910_IRQ_RTC_ALARM;
> > +	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> > +		tps65910_rtc_interrupt, IRQF_TRIGGER_LOW,
> > +		dev_name(&tps_rtc->rtc->dev), &pdev->dev);
> 
> How does this work? It doesn't look like tps_rtc->rtc is assigned until
> down there at the rtc_device_register() call.
> 

Somehow this got skipped. Thanks for pointing out.
Will fix and push as part of next patch.
 

> > +	if (ret < 0) {
> > +		dev_err(&pdev->dev, "IRQ is not free.\n");
> > +		return ret;
> > +	}
> > +	device_init_wakeup(&pdev->dev, 1);
> > +
> > +	tps_rtc->rtc = rtc_device_register(pdev->name, &pdev->dev,
> > +		&tps65910_rtc_ops, THIS_MODULE);
> > +	if (IS_ERR(tps_rtc->rtc)) {
> > +		ret = PTR_ERR(tps_rtc->rtc);
> > +		dev_err(&pdev->dev, "RTC device register: err %d\n", ret);
> > +		return ret;
> > +	}
> > +
> 
> --
> Sent by an employee of the Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum.

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