linux-kernel - Re: [PATCH v2 1/2] rtc: Add driver for Sunplus SP7021

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Date:   Mon, 29 Nov 2021 10:45:23 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Vincent Shih <vincent.sunplus@...il.com>, a.zummo@...ertech.it,
        alexandre.belloni@...tlin.com, linux-kernel@...r.kernel.org,
        linux-rtc@...r.kernel.org, robh+dt@...nel.org,
        devicetree@...r.kernel.org, wells.lu@...plus.com,
        in-reply-to=1635834123-24668-1-git-send-email-vincent.shih@...plus.com
Cc:     Vincent Shih <vincent.shih@...plus.com>
Subject: Re: [PATCH v2 1/2] rtc: Add driver for Sunplus SP7021

Hi Vincent,

On Tue, 2021-11-09 at 14:38 +0800, Vincent Shih wrote:
[...]
> +struct sunplus_rtc {
> +	struct clk *rtcclk;
> +	struct reset_control *rstc;
> +	void __iomem *base;
> +	u32 ohms;
> +};
> +
> +struct sunplus_rtc sp_rtc;

Why is this global?


[...]
> +static int sp_rtc_probe(struct platform_device *plat_dev)
> +{
> +	struct rtc_device *rtc;
> +	struct resource *res;
> +	const struct rtc_class_ops *rtc_ops;
> +	void __iomem *reg_base;
> +	int ret, irq;
> +
> +	memset(&sp_rtc, 0, sizeof(sp_rtc));

I'd allocate device private data here with devm_kzalloc() instead.

> +	// find and map our resources
> +	res = platform_get_resource_byname(plat_dev, IORESOURCE_MEM, RTC_REG_NAME);
> +
> +	if (res) {
> +		dev_dbg(&plat_dev->dev, "res = 0x%x\n", res->start);
> +
> +		reg_base = devm_ioremap_resource(&plat_dev->dev, res);

There is no need to check res before feeding it into
devm_ioremap_resource(). You can simplify this even further with
devm_platform_ioremap_resource_by_name().

> +		if (IS_ERR(reg_base)) {
> +			dev_err(&plat_dev->dev, "%s devm_ioremap_resource fail\n", RTC_REG_NAME);
> +			return PTR_ERR(reg_base);
> +		}
> +
> +		dev_dbg(&plat_dev->dev, "reg_base = 0x%lx\n", (unsigned long)reg_base);
> +	}
> +
> +	sp_rtc.base = reg_base;
> +	rtc_ops = &sp_rtc_ops;
> +
> +	// Keep RTC from system reset
> +	writel(DIS_SYS_RST_RTC_MASK | DIS_SYS_RST_RTC, sp_rtc.base + RTC_CTRL);

Are you allowed to write to sp_rtc.base registers before releasing the
reset?

> +	// request irq
> +	irq = platform_get_irq(plat_dev, 0);
> +	if (irq < 0) {
> +		dev_err(&plat_dev->dev, "platform_get_irq failed\n");
> +		irq = IRQ_NOTCONNECTED;

By doing this you are making devm_request_irq() below return -ENOTCONN.
Why not return the real error code right here?

		return dev_err_probe(&plat_dev->dev, irq, "platform_get_irq failed\n");

> +	}
> +
> +	ret = devm_request_irq(&plat_dev->dev, irq, rtc_irq_handler,
> +					IRQF_TRIGGER_RISING, "rtc irq", plat_dev);
> +	if (ret) {
> +		dev_err(&plat_dev->dev, "devm_request_irq failed: %d\n", ret);
> +		return ret;

This could be shortened to:

		return dev_err_probe(&plat_dev->dev, ret, "devm_request_irq failed\n");

> +	}
> +
> +	// Setup trickle charger
> +	if (plat_dev->dev.of_node)
> +		sp_rtc_set_trickle_charger(plat_dev->dev);
> +
> +	// reset
> +	sp_rtc.rstc = devm_reset_control_get_exclusive(&plat_dev->dev, NULL);
> +	if (IS_ERR(sp_rtc.rstc)) {
> +		ret = dev_err_probe(&plat_dev->dev, PTR_ERR(sp_rtc.rstc),
> +					    "failed to retrieve reset controller\n");
> +		return PTR_ERR(sp_rtc.rstc);

This could be shortened to:

		return dev_err_probe(&plat_dev->dev, PTR_ERR(sp_rtc.rstc),
				     "failed to retrieve reset controller\n");

> +	}
> +
> +	// clk
> +	sp_rtc.rtcclk = devm_clk_get(&plat_dev->dev, NULL);
> +	if (IS_ERR(sp_rtc.rtcclk)) {
> +		dev_err(&plat_dev->dev, "devm_clk_get fail\n");
> +		return PTR_ERR(sp_rtc.rtcclk);


> +	}
> +
> +	ret = reset_control_deassert(sp_rtc.rstc);
> +	if (ret)
> +		return ret;
> +
> +	ret = clk_prepare_enable(sp_rtc.rtcclk);
> +	if (ret)

Assert reset on failure?

> +		return ret;
> +
> +	device_init_wakeup(&plat_dev->dev, 1);
> +
> +	rtc = devm_rtc_allocate_device(&plat_dev->dev);
> +	if (IS_ERR(rtc))

Disable clock and assert reset on failure?

> +		return PTR_ERR(rtc);
> +
> +	rtc->range_max = U32_MAX;
> +	rtc->range_min = 0;
> +	rtc->ops = rtc_ops;
> +
> +	ret = devm_rtc_register_device(rtc);
> +	if (ret)
> +		goto free_reset_assert_clk;
> +
> +	platform_set_drvdata(plat_dev, rtc);
> +	dev_info(&plat_dev->dev, "sp7021-rtc loaded\n");
> +
> +	return 0;
> +
> +free_reset_assert_clk:
> +	reset_control_assert(sp_rtc.rstc);
> +	clk_disable_unprepare(sp_rtc.rtcclk);

Should this be the other way around? I'd expect this to be in the
opposite order of reset deassert and clock enable.

> +
> +	return ret;
> +}
> +
> +static int sp_rtc_remove(struct platform_device *plat_dev)
> +{
> +	reset_control_assert(sp_rtc.rstc);
> +	clk_disable_unprepare(sp_rtc.rtcclk);

Same as above.

regards
Philipp