Hello Romain,

On 20/07/2021 19:22:50+0200, Romain Perier wrote:

|| COMPILE_TEST maybe ?

+	help
+	  If you say yes here you get support for the Mstar MSC313e On-Chip
+	  Real Time Clock.
+
+	  This driver can also be built as a module, if so, the module
+	  will be called "rtc-msc313".
+
 endif # RTC_CLASS

+static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct msc313_rtc *priv = dev_get_drvdata(dev);
+	u32 seconds;
+	u16 reg;
+
+	reg = readw(priv->rtc_base + REG_RTC_CTRL);
+	writew(reg | READ_EN_BIT, priv->rtc_base + REG_RTC_CTRL);
+
+	/* Wait for HW latch done */
+	while (readw(priv->rtc_base + REG_RTC_CTRL) & READ_EN_BIT)
+		udelay(1);
+
+	seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L)
+			| (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
+
+	rtc_time64_to_tm(seconds, tm);
+
+	return rtc_valid_tm(tm);

This is not necessary, tm is valid at that point (and the core will
check anyway).

+}
+
+static int msc313_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct msc313_rtc *priv = dev_get_drvdata(dev);
+	unsigned long seconds;
+	u16 reg;
+
+	seconds = rtc_tm_to_time64(tm);
+	writew(seconds & 0xFFFF, priv->rtc_base + REG_RTC_LOAD_VAL_L);
+	writew((seconds >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_LOAD_VAL_H);
+	reg = readw(priv->rtc_base + REG_RTC_CTRL);
+	writew(reg | LOAD_EN_BIT, priv->rtc_base + REG_RTC_CTRL);
+
+	/* need to check carefully if we want to clear REG_RTC_LOAD_VAL_H for customer*/
+	while (readw(priv->rtc_base + REG_RTC_CTRL) & LOAD_EN_BIT)
+		udelay(1);
+	writew(0, priv->rtc_base + REG_RTC_LOAD_VAL_H);

Why is that necessary? The comment is not super useful here.

+
+	return 0;
+}
+
+static const struct rtc_class_ops msc313_rtc_ops = {
+	.read_time = msc313_rtc_read_time,
+	.set_time = msc313_rtc_set_time,
+	.read_alarm = msc313_rtc_read_alarm,
+	.set_alarm = msc313_rtc_set_alarm,
+	.alarm_irq_enable = msc313_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t msc313_rtc_interrupt(s32 irq, void *dev_id)
+{
+	struct msc313_rtc *priv = dev_get_drvdata(dev_id);
+	u16 reg;
+
+	reg = readw_relaxed(priv->rtc_base + REG_RTC_CTRL);
+	reg |= INT_CLEAR_BIT;
+	reg &= ~INT_FORCE_BIT;
+	writew_relaxed(reg, priv->rtc_base + REG_RTC_CTRL);
+

I'm not convinced the _relaxed functions are doing the right thing here.
Also, shouldn't you check the alarm actually fired?

+	rtc_update_irq(priv->rtc_dev, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int msc313_rtc_remove(struct platform_device *pdev)
+{
+	struct msc313_rtc *priv = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(priv->clk);

With a nice devm_add_action_or_reset() in the probe, you can remove the
need for msc313_rtc_remove().

+
+	return 0;
+}
+
+static int msc313_rtc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct msc313_rtc *priv;
+	int ret;
+	int irq;
+	unsigned long rate;
+	u16 reg;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(struct msc313_rtc), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->rtc_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->rtc_base))
+		return PTR_ERR(priv->rtc_base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return -EINVAL;
+
+	ret = devm_request_irq(dev, irq, msc313_rtc_interrupt, IRQF_SHARED,
+			       dev_name(&pdev->dev), &pdev->dev);
+	if (ret) {
+		dev_err(dev, "Unable to request irq\n");
+		return ret;
+	}
+
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		dev_err(dev, "No input reference clock\n");
+		return PTR_ERR(priv->clk);
+	}
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret) {
+		dev_err(dev, "Failed to enable the reference clock, %d\n", ret);
+		return ret;
+	}
+
+	rate = clk_get_rate(priv->clk);
+
+	reg = readw(priv->rtc_base + REG_RTC_CTRL);
+	if (!(reg & SOFT_RSTZ_BIT)) {
+		reg |= SOFT_RSTZ_BIT;
+		writew(reg, priv->rtc_base + REG_RTC_CTRL);
+	}

What is the meaning of this bit? I would think it is better to use that
to know whether the RTC holds the correct time instead of killing the
info here.

+
+	writew(rate & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_L);
+	writew((rate >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_H);
+
+	reg |= CNT_EN_BIT;
+	writew(reg, priv->rtc_base + REG_RTC_CTRL);
+
+	platform_set_drvdata(pdev, priv);
+
+	priv->rtc_dev = devm_rtc_device_register(dev, dev_name(dev), &msc313_rtc_ops, THIS_MODULE);
+	if (IS_ERR(priv->rtc_dev)) {
+		dev_err(dev, "Failed to register rtc device\n");
+		return PTR_ERR(priv->rtc_dev);
+	}

Please switch to devm_rtc_allocate_device and devm_rtc_register_device.
Also drop the error message, it is not necessary.

You must also set the RTC range. To help you, you can use:
https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/rtc-tools.git/tree/rtc-range.c
then you must update the DT bindings as the RTC will support the
start-year property

You must also run rtctest and should include the results.


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