Re: [PATCH 2/3] rtc: Add Raspberry Pi 5 RTC driver

From: Jonathan Bell <redacted>

Upstreaming the downstream Raspberry Pi 5 RTC driver.
This driver supports the custom DA9091, which is accessed through the firmware mailbox.

Co-developed-by: Dom Cobley <redacted>
Signed-off-by: Sander Speetjens <redacted>
---
 drivers/rtc/Kconfig   |  11 ++
 drivers/rtc/Makefile  |   1 +
 drivers/rtc/rtc-rpi.c | 277 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 289 insertions(+)
 create mode 100644 drivers/rtc/rtc-rpi.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 05b9233b9418..382973d46e06 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig

@@ -1999,6 +1999,17 @@ config RTC_DRV_R7301
 	   This driver can also be built as a module. If so, the module
 	   will be called rtc-r7301.
 
+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_STM32
 	tristate "STM32 RTC"
 	select REGMAP_MMIO

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 0347645b021f..78551bb04c5c 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile

@@ -148,6 +148,7 @@ obj-$(CONFIG_RTC_DRV_RC5T583)	+= rtc-rc5t583.o
 obj-$(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

diff --git a/drivers/rtc/rtc-rpi.c b/drivers/rtc/rtc-rpi.c
new file mode 100644
index 000000000000..e455b4116957
--- /dev/null
+++ b/drivers/rtc/rtc-rpi.c

@@ -0,0 +1,277 @@
+// 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;
+	u32 bbat_vchg_microvolts;
+};
+
+#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,
+	RTC_BBAT_CHG_VOLTS,
+	RTC_BBAT_CHG_VOLTS_MIN,
+	RTC_BBAT_CHG_VOLTS_MAX,
+	RTC_BBAT_VOLTS
+};
+
+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_set_charge_voltage(struct device *dev)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev);
+	u32 data[2] = {RTC_BBAT_CHG_VOLTS, vrtc->bbat_vchg_microvolts};
+	int err;
+
+	err = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_SET_RTC_REG,
+				    &data, sizeof(data));
+
+	if (err)
+		dev_err(dev, "failed to set trickle charge voltage to %uuV: %d\n",
+			vrtc->bbat_vchg_microvolts, err);
+	else if (vrtc->bbat_vchg_microvolts)
+		dev_info(dev, "trickle charging enabled at %uuV\n",
+			 vrtc->bbat_vchg_microvolts);
+
+	return err;
+}
+
+static ssize_t rpi_rtc_print_uint_reg(struct device *dev, char *buf, u32 reg)
+{
+	struct rpi_rtc_data *vrtc = dev_get_drvdata(dev->parent);
+	u32 data[2] = {reg, 0};
+	int ret = 0;
+
+	ret = rpi_firmware_property(vrtc->fw, RPI_FIRMWARE_GET_RTC_REG,
+				    &data, sizeof(data));
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%u\n", data[1]);
+}
+
+static ssize_t charging_voltage_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	return rpi_rtc_print_uint_reg(dev, buf, RTC_BBAT_CHG_VOLTS);
+}
+static DEVICE_ATTR_RO(charging_voltage);
+
+static ssize_t charging_voltage_min_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	return rpi_rtc_print_uint_reg(dev, buf, RTC_BBAT_CHG_VOLTS_MIN);
+}
+static DEVICE_ATTR_RO(charging_voltage_min);
+
+static ssize_t charging_voltage_max_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	return rpi_rtc_print_uint_reg(dev, buf, RTC_BBAT_CHG_VOLTS_MAX);
+}
+static DEVICE_ATTR_RO(charging_voltage_max);
+
+static ssize_t battery_voltage_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	return rpi_rtc_print_uint_reg(dev, buf, RTC_BBAT_VOLTS);
+}
+static DEVICE_ATTR_RO(battery_voltage);
+
+static struct attribute *rpi_rtc_attrs[] = {
+	&dev_attr_charging_voltage.attr,
+	&dev_attr_charging_voltage_min.attr,
+	&dev_attr_charging_voltage_max.attr,
+	&dev_attr_battery_voltage.attr,
+	NULL
+};
+
+static const struct attribute_group rpi_rtc_sysfs_files = {
+	.attrs = rpi_rtc_attrs,
+};