rtc: Add Amlogic Virtual Wake RTC

The Amlogic Meson GX SoCs uses a special register to store the
time in seconds to wakeup after a system suspend.

In order to be able to reuse the RTC wakealarm feature, this
driver implements a fake RTC device which uses the system time
to deduce a suspend delay.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
[khilman: rebase to v5.3-rc, rework and modernization]
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20190812232850.8016-3-khilman@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

MAINTAINERS

@@ -1443,6 +1443,7 @@ F:	arch/arm64/boot/dts/amlogic/
 F:	drivers/pinctrl/meson/
 F:	drivers/mmc/host/meson*
 F:	drivers/soc/amlogic/
+F:	drivers/rtc/rtc-meson*
 N:	meson
 
 ARM/Amlogic Meson SoC Sound Drivers

drivers/rtc/Kconfig

@@ -373,6 +373,17 @@ config RTC_DRV_MAX77686
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-max77686.
 
+config RTC_DRV_MESON_VRTC
+	tristate "Amlogic Meson Virtual RTC"
+	depends on ARCH_MESON || COMPILE_TEST
+	default m if ARCH_MESON
+	help
+	  If you say yes here you will get support for the
+	  Virtual RTC of Amlogic SoCs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-meson-vrtc.
+
 config RTC_DRV_RK808
 	tristate "Rockchip RK805/RK808/RK809/RK817/RK818 RTC"
 	depends on MFD_RK808

drivers/rtc/Makefile

@@ -102,6 +102,7 @@ obj-$(CONFIG_RTC_DRV_MAX8907)	+= rtc-max8907.o
 obj-$(CONFIG_RTC_DRV_MAX8925)	+= rtc-max8925.o
 obj-$(CONFIG_RTC_DRV_MAX8997)	+= rtc-max8997.o
 obj-$(CONFIG_RTC_DRV_MAX8998)	+= rtc-max8998.o
+obj-$(CONFIG_RTC_DRV_MESON_VRTC)+= rtc-meson-vrtc.o
 obj-$(CONFIG_RTC_DRV_MC13XXX)	+= rtc-mc13xxx.o
 obj-$(CONFIG_RTC_DRV_MCP795)	+= rtc-mcp795.o
 obj-$(CONFIG_RTC_DRV_MESON)	+= rtc-meson.o

drivers/rtc/rtc-meson-vrtc.c

@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 BayLibre, SAS
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ * Copyright (C) 2015 Amlogic, Inc. All rights reserved.
+ */
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/time64.h>
+
+struct meson_vrtc_data {
+	void __iomem *io_alarm;
+	struct rtc_device *rtc;
+	unsigned long alarm_time;
+	bool enabled;
+};
+
+static int meson_vrtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct timespec64 time;
+
+	dev_dbg(dev, "%s\n", __func__);
+	ktime_get_raw_ts64(&time);
+	rtc_time64_to_tm(time.tv_sec, tm);
+
+	return 0;
+}
+
+static void meson_vrtc_set_wakeup_time(struct meson_vrtc_data *vrtc,
+				       unsigned long time)
+{
+	writel_relaxed(time, vrtc->io_alarm);
+}
+
+static int meson_vrtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct meson_vrtc_data *vrtc = dev_get_drvdata(dev);
+
+	dev_dbg(dev, "%s: alarm->enabled=%d\n", __func__, alarm->enabled);
+	if (alarm->enabled)
+		vrtc->alarm_time = rtc_tm_to_time64(&alarm->time);
+	else
+		vrtc->alarm_time = 0;
+
+	return 0;
+}
+
+static int meson_vrtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct meson_vrtc_data *vrtc = dev_get_drvdata(dev);
+
+	vrtc->enabled = enabled;
+	return 0;
+}
+
+static const struct rtc_class_ops meson_vrtc_ops = {
+	.read_time = meson_vrtc_read_time,
+	.set_alarm = meson_vrtc_set_alarm,
+	.alarm_irq_enable = meson_vrtc_alarm_irq_enable,
+};
+
+static int meson_vrtc_probe(struct platform_device *pdev)
+{
+	struct meson_vrtc_data *vrtc;
+	int ret;
+
+	vrtc = devm_kzalloc(&pdev->dev, sizeof(*vrtc), GFP_KERNEL);
+	if (!vrtc)
+		return -ENOMEM;
+
+	vrtc->io_alarm = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(vrtc->io_alarm))
+		return PTR_ERR(vrtc->io_alarm);
+
+	device_init_wakeup(&pdev->dev, 1);
+
+	platform_set_drvdata(pdev, vrtc);
+
+	vrtc->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(vrtc->rtc))
+		return PTR_ERR(vrtc->rtc);
+
+	vrtc->rtc->ops = &meson_vrtc_ops;
+	ret = rtc_register_device(vrtc->rtc);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int meson_vrtc_suspend(struct device *dev)
+{
+	struct meson_vrtc_data *vrtc = dev_get_drvdata(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+	if (vrtc->alarm_time) {
+		unsigned long local_time;
+		long alarm_secs;
+		struct timespec64 time;
+
+		ktime_get_raw_ts64(&time);
+		local_time = time.tv_sec;
+
+		dev_dbg(dev, "alarm_time = %lus, local_time=%lus\n",
+			vrtc->alarm_time, local_time);
+		alarm_secs = vrtc->alarm_time - local_time;
+		if (alarm_secs > 0) {
+			meson_vrtc_set_wakeup_time(vrtc, alarm_secs);
+			dev_dbg(dev, "system will wakeup in %lds.\n",
+				alarm_secs);
+		} else {
+			dev_err(dev, "alarm time already passed: %lds.\n",
+				alarm_secs);
+		}
+	}
+
+	return 0;
+}
+
+static int meson_vrtc_resume(struct device *dev)
+{
+	struct meson_vrtc_data *vrtc = dev_get_drvdata(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	vrtc->alarm_time = 0;
+	meson_vrtc_set_wakeup_time(vrtc, 0);
+	return 0;
+}
+#endif
+static SIMPLE_DEV_PM_OPS(meson_vrtc_pm_ops,
+			 meson_vrtc_suspend, meson_vrtc_resume);
+
+static const struct of_device_id meson_vrtc_dt_match[] = {
+	{ .compatible = "amlogic,meson-vrtc"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, meson_vrtc_dt_match);
+
+static struct platform_driver meson_vrtc_driver = {
+	.probe = meson_vrtc_probe,
+	.driver = {
+		.name = "meson-vrtc",
+		.of_match_table = meson_vrtc_dt_match,
+		.pm = &meson_vrtc_pm_ops,
+	},
+};
+
+module_platform_driver(meson_vrtc_driver);
+
+MODULE_DESCRIPTION("Amlogic Virtual Wakeup RTC Timer driver");
+MODULE_LICENSE("GPL");