linux-kernel - Re: [PATCH v10 2/2] rtc: sophgo: add rtc support for Sophgo CV1800 SoC

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Message-ID: <20250213205818f14edd30@mail.local>
Date: Thu, 13 Feb 2025 21:58:18 +0100
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: Alexander Sverdlin <alexander.sverdlin@...il.com>
Cc: linux-riscv@...ts.infradead.org, linux-rtc@...r.kernel.org,
	Jingbao Qiu <qiujingbao.dlmu@...il.com>,
	Inochi Amaoto <inochiama@...il.com>, robh@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	unicorn_wang@...look.com, inochiama@...look.com,
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	dlan@...too.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 2/2] rtc: sophgo: add rtc support for Sophgo CV1800
 SoC

On 13/02/2025 19:46:15+0100, Alexander Sverdlin wrote:
> +static int cv1800_rtc_probe(struct platform_device *pdev)
> +{
> +	struct cv1800_rtc_priv *rtc;
> +	u32 ctrl_val;
> +	void __iomem *base;
> +	int ret;
> +
> +	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
> +	if (!rtc)
> +		return -ENOMEM;
> +
> +	base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	rtc->rtc_map = devm_regmap_init_mmio(&pdev->dev, base,
> +					     &cv1800_rtc_regmap_config);
> +	if (IS_ERR(rtc->rtc_map))
> +		return PTR_ERR(rtc->rtc_map);
> +
> +	rtc->irq = platform_get_irq(pdev, 0);
> +	if (rtc->irq < 0)
> +		return rtc->irq;
> +
> +	rtc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	if (IS_ERR(rtc->clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(rtc->clk),
> +				     "clk not found\n");
> +
> +	platform_set_drvdata(pdev, rtc);
> +
> +	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 = &cv1800_rtc_ops;
> +	rtc->rtc_dev->range_max = U32_MAX;
> +
> +	ret = devm_request_irq(&pdev->dev, rtc->irq, cv1800_rtc_irq_handler,
> +			       IRQF_TRIGGER_HIGH, "rtc alarm", rtc);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret,
> +				     "cannot register interrupt handler\n");
> +
> +	rtc_enable_sec_counter(rtc);

Really, this must be avoided, this loses precious information and
changing it later will break users. What must be done is to check
whether the RTC is started in .read_time if this is not the case, return
-EINVAL instead of an invalid date/time.
The RTC must be started once the time is set for the first time. This
ensures we can detect when the time is invalid.


> +
> +	return devm_rtc_register_device(rtc->rtc_dev);
> +}
> +
> +static const struct of_device_id cv1800_dt_ids[] = {
> +	{ .compatible = "sophgo,cv1800-rtc" },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, cv1800_dt_ids);
> +
> +static struct platform_driver cv1800_rtc_driver = {
> +	.driver = {
> +		.name = "sophgo-cv1800-rtc",
> +		.of_match_table = cv1800_dt_ids,
> +	},
> +	.probe = cv1800_rtc_probe,
> +};
> +
> +module_platform_driver(cv1800_rtc_driver);
> +MODULE_AUTHOR("Jingbao Qiu");
> +MODULE_DESCRIPTION("Sophgo cv1800 RTC Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.48.1
> 

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