linux-kernel - Re: [PATCH v3 1/2] rtc: Add driver for Microchip PolarFire SoC

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Message-ID: <YoQO9or6g2r3EU8w@mail.local>
Date:   Tue, 17 May 2022 23:09:10 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     a.zummo@...ertech.it, daire.mcnamara@...rochip.com,
        lewis.hanly@...rochip.com, linux-kernel@...r.kernel.org,
        linux-rtc@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] rtc: Add driver for Microchip PolarFire SoC

Hello,

On 16/05/2022 09:28:38+0100, Conor Dooley wrote:
> +struct mpfs_rtc_dev {
> +	struct rtc_device *rtc;
> +	void __iomem *base;
> +	int wakeup_irq;

I believe this is only used in .probe so you make it local to this
function.

> +};
> +


> +static int mpfs_rtc_readtime(struct device *dev, struct rtc_time *tm)
> +{
> +	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
> +	u64 time;
> +
> +	time = ((u64)readl(rtcdev->base + DATETIME_UPPER_REG) & DATETIME_UPPER_MASK) << 32;
> +	time |= readl(rtcdev->base + DATETIME_LOWER_REG);

Are the registers properly latched on a DATETIME_UPPER_REG read?

> +	rtc_time64_to_tm(time + rtcdev->rtc->range_min, tm);

range_min is never set so it will end up being 0. I guess you can avoid
a bunch of arithmetic in all the driver. Offsetting will happen in the
core which will probably never happen anyway because the max year is
141338. I guess we will all be gone by then ;)

> +
> +	return 0;
> +}
> +

> +static int mpfs_rtc_probe(struct platform_device *pdev)
> +{
> +	struct mpfs_rtc_dev *rtcdev;
> +	struct clk *clk;
> +	u32 prescaler;
> +	int ret;
> +
> +	rtcdev = devm_kzalloc(&pdev->dev, sizeof(struct mpfs_rtc_dev), GFP_KERNEL);
> +	if (!rtcdev)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, rtcdev);
> +
> +	rtcdev->rtc = devm_rtc_allocate_device(&pdev->dev);
> +	if (IS_ERR(rtcdev->rtc))
> +		return PTR_ERR(rtcdev->rtc);
> +
> +	rtcdev->rtc->ops = &mpfs_rtc_ops;
> +
> +	/* range is capped by alarm max, lower reg is 31:0 & upper is 10:0 */
> +	rtcdev->rtc->range_max = GENMASK_ULL(42, 0);
> +
> +	clk = mpfs_rtc_init_clk(&pdev->dev);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	rtcdev->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(rtcdev->base)) {
> +		dev_dbg(&pdev->dev, "invalid ioremap resources\n");
> +		return PTR_ERR(rtcdev->base);
> +	}
> +
> +	rtcdev->wakeup_irq = platform_get_irq(pdev, 0);
> +	if (rtcdev->wakeup_irq <= 0) {
> +		dev_dbg(&pdev->dev, "could not get wakeup irq\n");
> +		return rtcdev->wakeup_irq;
> +	}
> +	ret = devm_request_irq(&pdev->dev, rtcdev->wakeup_irq, mpfs_rtc_wakeup_irq_handler, 0,
> +			       dev_name(&pdev->dev), rtcdev);
> +	if (ret) {
> +		dev_dbg(&pdev->dev, "could not request wakeup irq\n");
> +		return ret;
> +	}
> +
> +	/* prescaler hardware adds 1 to reg value */
> +	prescaler = clk_get_rate(devm_clk_get(&pdev->dev, "rtcref")) - 1;
> +
> +	if (prescaler > MAX_PRESCALER_COUNT) {
> +		dev_dbg(&pdev->dev, "invalid prescaler %d\n", prescaler);
> +		return -EINVAL;
> +	}
> +
> +	writel(prescaler, rtcdev->base + PRESCALER_REG);
> +	dev_info(&pdev->dev, "prescaler set to: 0x%X \r\n", prescaler);
> +
> +	device_init_wakeup(&pdev->dev, true);
> +	ret = dev_pm_set_wake_irq(&pdev->dev, rtcdev->wakeup_irq);
> +	if (ret)
> +		dev_err(&pdev->dev, "failed to enable irq wake\n");
> +
> +	return devm_rtc_register_device(rtcdev->rtc);
> +}
> +
> +static int mpfs_rtc_remove(struct platform_device *pdev)
> +{
> +	mpfs_rtc_alarm_irq_enable(&pdev->dev, 0);

This is not something you want to do if you want to wake up from
hibernate or any similar sleep state.

> +	device_init_wakeup(&pdev->dev, 0);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id mpfs_rtc_of_match[] = {
> +	{ .compatible = "microchip,mpfs-rtc" },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, mpfs_rtc_of_match);
> +
> +static struct platform_driver mpfs_rtc_driver = {
> +	.probe = mpfs_rtc_probe,
> +	.remove = mpfs_rtc_remove,
> +	.driver	= {
> +		.name = "mpfs_rtc",
> +		.of_match_table = mpfs_rtc_of_match,
> +	},
> +};
> +
> +module_platform_driver(mpfs_rtc_driver);
> +
> +MODULE_DESCRIPTION("Real time clock for Microchip Polarfire SoC");
> +MODULE_AUTHOR("Daire McNamara <daire.mcnamara@...rochip.com>");
> +MODULE_AUTHOR("Conor Dooley <conor.dooley@...rochip.com>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.36.1
> 

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