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

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Message-ID: <2025081113090716407d59@mail.local>
Date: Mon, 11 Aug 2025 15:09:07 +0200
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: ot_shunxi.zhang@...iatek.com
Cc: Eddie Huang <eddie.huang@...iatek.com>,
	Sean Wang <sean.wang@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Lee Jones <lee@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-rtc@...r.kernel.org,
	linux-kernel@...r.kernel.org, sirius.wang@...iatek.com,
	vince-wl.liu@...iatek.com, jh.hsu@...iatek.com
Subject: Re: [PATCH v1 2/2] rtc: mt6397: Add BBPU alarm status reset and
 shutdown handling

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?

> +}
> +
>  #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://bootlin.com