openwrt/target/linux/bcm27xx/patches-6.1/950-0919-rtc-rtc-rpi-Add-simple-RTC-driver-for-Raspberry-Pi.patch

From 222dedcdc09247126d39364a614ff2019789f52a Mon Sep 17 00:00:00 2001
From: Dom Cobley <popcornmix@gmail.com>
Date: Fri, 7 Jul 2023 20:00:45 +0100
Subject: [PATCH] rtc: rtc-rpi: Add simple RTC driver for Raspberry Pi

This supports setting and reading the real time clock
and supports wakeup alarms.

To support wake up alarms you want this bootloader config:
 POWER_OFF_ON_HALT=1
 WAKE_ON_GPIO=0

You can test with:
  echo +600 | sudo tee /sys/class/rtc/rtc0/wakealarm
  sudo halt

That will halt (in an almost no power state),
then wake and restart after 10 minutes.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
---
 drivers/rtc/Kconfig   |  11 +++
 drivers/rtc/Makefile  |   1 +
 drivers/rtc/rtc-rpi.c | 177 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 189 insertions(+)
 create mode 100644 drivers/rtc/rtc-rpi.c

--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -223,6 +223,17 @@ config RTC_DRV_AC100
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ac100.
 
+config RTC_DRV_RPI
+	tristate "Raspberry Pi RTC"
+	depends on ARCH_BRCMSTB || COMPILE_TEST
+	default ARCH_BRCMSTB
+	help
+	  If you say yes here you get support for the RTC found on
+	  Raspberry Pi devices.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-rpi.
+
 config RTC_DRV_BRCMSTB
 	tristate "Broadcom STB wake-timer"
 	depends on ARCH_BRCMSTB || BMIPS_GENERIC || COMPILE_TEST
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -140,6 +140,7 @@ obj-$(CONFIG_RTC_DRV_RC5T583)	+= rtc-rc5
 obj-$(CONFIG_RTC_DRV_RC5T619)	+= rtc-rc5t619.o
 obj-$(CONFIG_RTC_DRV_RK808)	+= rtc-rk808.o
 obj-$(CONFIG_RTC_DRV_RP5C01)	+= rtc-rp5c01.o
+obj-$(CONFIG_RTC_DRV_RPI)	+= rtc-rpi.o
 obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
--- /dev/null
+++ b/drivers/rtc/rtc-rpi.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+/**
+ * rtc-rpi.c
+ *
+ * RTC driver using firmware mailbox
+ * Supports battery backed RTC and wake alarms
+ *
+ * Based on rtc-meson-vrtc by Neil Armstrong
+ *
+ * Copyright (c) 2023, Raspberry Pi Ltd.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/of.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+struct rpi_rtc_data {
+	struct rtc_device *rtc;
+	struct rpi_firmware *fw;
+};
+
+#define RPI_FIRMWARE_GET_RTC_REG 0x00030087
+#define RPI_FIRMWARE_SET_RTC_REG 0x00038087
+enum {RTC_TIME, RTC_ALARM, RTC_ALARM_PENDING, RTC_ALARM_ENABLE};
+
+static int rpi_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_TIME};
+	int err;
+
+	err = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_GET_RTC_REG,
+				    &data, sizeof(data));
+	rtc_time64_to_tm(data[1], tm);
+	return err;
+}
+
+static int rpi_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_TIME, rtc_tm_to_time64(tm)};
+
+	return rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_SET_RTC_REG,
+				     &data, sizeof(data));
+}
+
+static int rpi_rtc_alarm_irq_is_enabled(struct device *dev, unsigned char *enabled)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_ALARM_ENABLE};
+	s32 err = 0;
+
+	err = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_GET_RTC_REG,
+				    &data, sizeof(data));
+	*enabled = data[1] & 0x1;
+	return err;
+}
+
+static int rpi_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_ALARM_ENABLE, enabled};
+
+	return rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_SET_RTC_REG,
+				     &data, sizeof(data));
+}
+
+static int rpi_rtc_alarm_clear_pending(struct device *dev)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_ALARM_PENDING, 1};
+
+	return rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_SET_RTC_REG,
+				     &data, sizeof(data));
+}
+
+static int rpi_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_ALARM};
+	s32 err = 0;
+
+	err = rpi_rtc_alarm_irq_is_enabled(dev, &alarm->enabled);
+	if (!err)
+		err = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_GET_RTC_REG,
+					    &data, sizeof(data));
+	rtc_time64_to_tm(data[1], &alarm->time);
+
+	return err;
+}
+
+static int rpi_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_ALARM, rtc_tm_to_time64(&alarm->time)};
+	int err;
+
+	err = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_SET_RTC_REG,
+				    &data, sizeof(data));
+
+	if (err == 0)
+		err = rpi_rtc_alarm_irq_enable(dev, alarm->enabled);
+
+	return err;
+}
+
+static const struct rtc_class_ops rpi_rtc_ops = {
+	.read_time = rpi_rtc_read_time,
+	.set_time = rpi_rtc_set_time,
+	.read_alarm = rpi_rtc_read_alarm,
+	.set_alarm = rpi_rtc_set_alarm,
+	.alarm_irq_enable = rpi_rtc_alarm_irq_enable,
+};
+
+static int rpi_rtc_probe(struct platform_device *pdev)
+{
+	struct rpi_rtc_data *vrtc;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *fw_node;
+	struct rpi_firmware *fw;
+	int ret;
+
+	fw_node = of_parse_phandle(np, "firmware", 0);
+	if (!fw_node) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = rpi_firmware_get(fw_node);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	vrtc = devm_kzalloc(&pdev->dev, sizeof(*vrtc), GFP_KERNEL);
+	if (!vrtc)
+		return -ENOMEM;
+
+	vrtc->fw = fw;
+
+	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);
+
+	set_bit(RTC_FEATURE_ALARM_WAKEUP_ONLY, vrtc->rtc->features);
+	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, vrtc->rtc->features);
+
+	vrtc->rtc->ops = &rpi_rtc_ops;
+	ret = devm_rtc_register_device(vrtc->rtc);
+
+	rpi_rtc_alarm_clear_pending(dev);
+	return ret;
+}
+
+static const struct of_device_id rpi_rtc_dt_match[] = {
+	{ .compatible = "raspberrypi,rpi-rtc"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, rpi_rtc_dt_match);
+
+static struct platform_driver rpi_rtc_driver = {
+	.probe = rpi_rtc_probe,
+	.driver = {
+		.name = "rpi-rtc",
+		.of_match_table = rpi_rtc_dt_match,
+	},
+};
+
+module_platform_driver(rpi_rtc_driver);
+
+MODULE_DESCRIPTION("Raspberry Pi RTC driver");
+MODULE_LICENSE("GPL");