linux-kernel - Re: Re: [PATCH v2 3/7] rtc: mt6397: improvements of rtc driver

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Message-ID: <20190705212448.GB12409@piout.net>
Date:   Fri, 5 Jul 2019 23:24:48 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Frank Wunderlich <frank-w@...lic-files.de>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Sebastian Reichel <sre@...nel.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-rtc@...r.kernel.org,
        Eddie Huang <eddie.huang@...iatek.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Richard Fontana <rfontana@...hat.com>,
        Allison Randal <allison@...utok.net>,
        "David S . Miller" <davem@...emloft.net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Josef Friedl <josef.friedl@...ed.at>
Subject: Re: Re: [PATCH v2 3/7] rtc: mt6397: improvements of rtc driver

On 05/07/2019 17:35:46+0200, Frank Wunderlich wrote:
> Hi Alexander,
> 
> thank you for the Review
> 
> > Gesendet: Donnerstag, 04. Juli 2019 um 22:43 Uhr
> > Von: "Alexandre Belloni" <alexandre.belloni@...tlin.com>
> > > -	rtc->rtc_dev = devm_rtc_allocate_device(rtc->dev);
> > > -	if (IS_ERR(rtc->rtc_dev))
> > > -		return PTR_ERR(rtc->rtc_dev);
> > > +	ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
> > > +					mtk_rtc_irq_handler_thread,
> > > +					IRQF_ONESHOT | IRQF_TRIGGER_HIGH,
> > > +					"mt6397-rtc", rtc);
> > >
> >
> > This change may lead to a crash and the allocation was intentionally
> > placed before the irq request.
> 
> i got no crash till now, but i will try to move the allocation before irq-request
> 

Let's say the RTC has been used to start your platform, then the irq
handler will be called as soon as the irq is requested, leading to a
null pointer dereference.

> > > -	ret = request_threaded_irq(rtc->irq, NULL,
> > > -				   mtk_rtc_irq_handler_thread,
> > > -				   IRQF_ONESHOT | IRQF_TRIGGER_HIGH,
> > > -				   "mt6397-rtc", rtc);
> > >  	if (ret) {
> > >  		dev_err(&pdev->dev, "Failed to request alarm IRQ: %d: %d\n",
> > >  			rtc->irq, ret);
> > > @@ -287,6 +281,10 @@ static int mtk_rtc_probe(struct platform_device *pdev)
> > >
> > >  	device_init_wakeup(&pdev->dev, 1);
> > >
> > > +	rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
> > > +	if (IS_ERR(rtc->rtc_dev))
> > > +		return PTR_ERR(rtc->rtc_dev);
> > > +
> > >  	rtc->rtc_dev->ops = &mtk_rtc_ops;
> 
> 
> > >  static const struct of_device_id mt6397_rtc_of_match[] = {
> > > +	{ .compatible = "mediatek,mt6323-rtc", },
> >
> > Unrelated change, this is not an improvement and must be accompanied by
> > a documentation change.
> 
> documentation is changed in 1/7 defining this compatible. i called it improvement because existing driver now supports another chip
> 

Yes and IIRC, I did comment that the rtc change also had to be separated
from 1/7.

Also, I really doubt this new compatible is necessary at all as you
could simply directly use mediatek,mt6397-rtc.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com