linux-kernel - Re: [PATCH v1 2/2] rtc: mt6397: Add BBPU alarm status reset and shutdown handling

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Message-ID: <81e8bd4a89545de7f05d19c2a7aafbaf11a5b203.camel@mediatek.com>
Date: Tue, 19 Aug 2025 07:48:38 +0000
From: Shunxi Zhang (章顺喜)
	<ot_shunxi.zhang@...iatek.com>
To: "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Eddie Huang (黃智傑) <eddie.huang@...iatek.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vince-WL Liu (劉文龍) <Vince-WL.Liu@...iatek.com>,
	Jh Hsu (許希孜) <Jh.Hsu@...iatek.com>, Sean Wang
	<Sean.Wang@...iatek.com>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "lee@...nel.org" <lee@...nel.org>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
	Sirius Wang (王皓昱) <Sirius.Wang@...iatek.com>
Subject: Re: [PATCH v1 2/2] rtc: mt6397: Add BBPU alarm status reset and
 shutdown handling

On Mon, 2025-08-11 at 15:09 +0200, Alexandre Belloni wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> On 11/08/2025 16:15:34+0800, ot_shunxi.zhang@...iatek.com wrote:
> > From: Shunxi Zhang <ot_shunxi.zhang@...iatek.com>
> > 
> > This patch introduces a new function,
> > mtk_rtc_reset_bbpu_alarm_status,
> > to reset the BBPU alarm status in the MT6397 RTC driver. This
> > function
> > writes the necessary bits to the RTC_BBPU register to clear the
> > alarm
> > status and ensure proper operation.
> > 
> > Additionally, the mtk_rtc_shutdown function is added to handle RTC
> > shutdown events. It resets the BBPU alarm status and updates the
> > RTC_IRQ_EN register to disable the one-shot alarm interrupt,
> > ensuring a clean shutdown process.
> > 
> > Signed-off-by: Shunxi Zhang <ot_shunxi.zhang@...iatek.com>
> > ---
> >  drivers/rtc/rtc-mt6397.c | 36 +++++++++++++++++++++++++++++++++++-
> >  1 file changed, 35 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
> > index 692c00ff544b..063bd399de8c 100644
> > --- a/drivers/rtc/rtc-mt6397.c
> > +++ b/drivers/rtc/rtc-mt6397.c
> > @@ -37,6 +37,21 @@ static int mtk_rtc_write_trigger(struct
> > mt6397_rtc *rtc)
> >       return ret;
> >  }
> > 
> > +static void mtk_rtc_reset_bbpu_alarm_status(struct mt6397_rtc
> > *rtc)
> > +{
> > +     u32 bbpu = RTC_BBPU_KEY | RTC_BBPU_PWREN | RTC_BBPU_RESET_AL;
> > +     int ret;
> > +
> > +     ret = regmap_write(rtc->regmap, rtc->addr_base + RTC_BBPU,
> > bbpu);
> > +     if (ret < 0) {
> > +             dev_err(rtc->rtc_dev->dev.parent, "%s: write rtc bbpu
> > error\n",
> > +                     __func__);
> > +             return;
> > +     }
> > +
> > +     mtk_rtc_write_trigger(rtc);
> > +}
> > +
> >  static irqreturn_t mtk_rtc_irq_handler_thread(int irq, void *data)
> >  {
> >       struct mt6397_rtc *rtc = data;
> > @@ -51,6 +66,8 @@ static irqreturn_t mtk_rtc_irq_handler_thread(int
> > irq, void *data)
> >               if (regmap_write(rtc->regmap, rtc->addr_base +
> > RTC_IRQ_EN,
> >                                irqen) == 0)
> >                       mtk_rtc_write_trigger(rtc);
> > +
> > +             mtk_rtc_reset_bbpu_alarm_status(rtc);
> >               mutex_unlock(&rtc->lock);
> > 
> >               return IRQ_HANDLED;
> > @@ -297,6 +314,22 @@ static int mtk_rtc_probe(struct
> > platform_device *pdev)
> >       return devm_rtc_register_device(rtc->rtc_dev);
> >  }
> > 
> > +static void mtk_rtc_shutdown(struct platform_device *pdev)
> > +{
> > +     struct mt6397_rtc *rtc = platform_get_drvdata(pdev);
> > +     int ret = 0;
> > +
> > +     mtk_rtc_reset_bbpu_alarm_status(rtc);
> > +
> > +     ret = regmap_update_bits(rtc->regmap,
> > +                              rtc->addr_base + RTC_IRQ_EN,
> > +                              RTC_IRQ_EN_ONESHOT_AL, 0);
> > +     if (ret < 0)
> > +             return;
> > +
> > +     mtk_rtc_write_trigger(rtc);
> 
> The whole goal of the RTC is to wakeup the system, why would you
> disable
> the alarm on shutdown?

Dear sir,
  I will remove the flow of "disable alarm shutdown"
in next version. thanks for your comments.  

Best regards
shunxi zhang

> 
> > +}
> > +
> >  #ifdef CONFIG_PM_SLEEP
> >  static int mt6397_rtc_suspend(struct device *dev)
> >  {
> > @@ -345,7 +378,8 @@ static struct platform_driver mtk_rtc_driver =
> > {
> >               .of_match_table = mt6397_rtc_of_match,
> >               .pm = &mt6397_pm_ops,
> >       },
> > -     .probe  = mtk_rtc_probe,
> > +     .probe = mtk_rtc_probe,
> > +     .shutdown = mtk_rtc_shutdown,
> >  };
> > 
> >  module_platform_driver(mtk_rtc_driver);
> > --
> > 2.46.0
> > 
> 
> --
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> 
https://urldefense.com/v3/__https://bootlin.com__;!!CTRNKA9wMg0ARbw!hGMitEEUU-sbH-rcMCMQ4Vlsn7NQeHdUrg9nEKYPyDME5fkbgsVciZd8SURxkvWA9Z1qX3oyNVZEWvVatYExZ8D7cFvdiyS_3Q_6$