linux-kernel - Re: [PATCH v5 6/7] rtc: support i.MX95 BBM RTC

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Message-ID: <202407112033378dbbea83@mail.local>
Date: Thu, 11 Jul 2024 22:33:37 +0200
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: Jonathan Corbet <corbet@....net>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Cristian Marussi <cristian.marussi@....com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Peng Fan <peng.fan@....com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, arm-scmi@...r.kernel.org,
	linux-rtc@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v5 6/7] rtc: support i.MX95 BBM RTC

Hello,

On 21/06/2024 15:04:41+0800, Peng Fan (OSS) wrote:
> +	ret = bbnsm->ops->rtc_time_get(ph, 0, &val);
> +	if (ret) {
> +		dev_err(dev, "%s: %d\n", __func__, ret);

This is not super useful, you should drop the various dev_err or pr_err
as there is no action the user can take to solve the erro apart from
retrying.

> +		return ret;
> +	}
> +
> +	rtc_time64_to_tm(val, tm);
> +
> +	return 0;
> +}
> +
> +static int scmi_imx_bbm_set_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
> +	struct scmi_protocol_handle *ph = bbnsm->ph;
> +	u64 val;
> +	int ret;
> +
> +	val = rtc_tm_to_time64(tm);
> +
> +	ret = bbnsm->ops->rtc_time_set(ph, 0, val);
> +	if (ret)
> +		dev_err(dev, "%s: %d\n", __func__, ret);
> +
> +	return ret;
> +}
> +
> +static int scmi_imx_bbm_alarm_irq_enable(struct device *dev, unsigned int enable)
> +{

How can userspace disable the alarm?

> +	return 0;
> +}
> +
> +static int scmi_imx_bbm_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
> +	struct scmi_protocol_handle *ph = bbnsm->ph;
> +	struct rtc_time *alrm_tm = &alrm->time;
> +	u64 val;
> +	int ret;
> +
> +	val = rtc_tm_to_time64(alrm_tm);
> +
> +	ret = bbnsm->ops->rtc_alarm_set(ph, 0, val);
> +	if (ret)
> +		dev_err(dev, "%s: %d\n", __func__, ret);
> +
> +	return ret;
> +}
> +
> +static const struct rtc_class_ops smci_imx_bbm_rtc_ops = {
> +	.read_time = scmi_imx_bbm_read_time,
> +	.set_time = scmi_imx_bbm_set_time,
> +	.set_alarm = scmi_imx_bbm_set_alarm,
> +	.alarm_irq_enable = scmi_imx_bbm_alarm_irq_enable,
> +};
> +
> +static int scmi_imx_bbm_rtc_notifier(struct notifier_block *nb, unsigned long event, void *data)
> +{
> +	struct scmi_imx_bbm *bbnsm = container_of(nb, struct scmi_imx_bbm, nb);
> +	struct scmi_imx_bbm_notif_report *r = data;
> +
> +	if (r->is_rtc)
> +		rtc_update_irq(bbnsm->rtc_dev, 1, RTC_AF | RTC_IRQF);
> +	else
> +		pr_err("Unexpected bbm event: %s\n", __func__);
> +
> +	return 0;
> +}
> +
> +static int scmi_imx_bbm_rtc_init(struct scmi_device *sdev)
> +{
> +	const struct scmi_handle *handle = sdev->handle;
> +	struct device *dev = &sdev->dev;
> +	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
> +	int ret;
> +
> +	bbnsm->rtc_dev = devm_rtc_allocate_device(dev);
> +	if (IS_ERR(bbnsm->rtc_dev))
> +		return PTR_ERR(bbnsm->rtc_dev);
> +
> +	bbnsm->rtc_dev->ops = &smci_imx_bbm_rtc_ops;
> +	bbnsm->rtc_dev->range_min = 0;

range_min is set to 0 by default, this is not necessary

> +	bbnsm->rtc_dev->range_max = U32_MAX;
> +
> +	ret = devm_rtc_register_device(bbnsm->rtc_dev);
> +	if (ret)
> +		return ret;
> +
> +	bbnsm->nb.notifier_call = &scmi_imx_bbm_rtc_notifier;
> +	return handle->notify_ops->devm_event_notifier_register(sdev, SCMI_PROTOCOL_IMX_BBM,
> +								SCMI_EVENT_IMX_BBM_RTC,
> +								NULL, &bbnsm->nb);

Note that failing after devm_rtc_register_device opens the driver to a
race condition as the character device will exist at that time.


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