[PATCH 2/3] rtc: Add Raspberry Pi 5 RTC driver
Sander Speetjens
sander.speetjens at gmail.com
Wed Sep 9 07:12:59 PDT 2026
From: Jonathan Bell <jonathan at raspberrypi.com>
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 <popcornmix at gmail.com>
Signed-off-by: Sander Speetjens <sander.speetjens at gmail.com>
---
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,
+};
+
+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 = rtc_add_group(vrtc->rtc, &rpi_rtc_sysfs_files);
+ if (ret)
+ return ret;
+
+ rpi_rtc_alarm_clear_pending(dev);
+
+ /*
+ * Optionally enable trickle charging - if the property isn't
+ * present (or set to zero), trickle charging is disabled.
+ */
+ of_property_read_u32(np, "trickle-charge-microvolt",
+ &vrtc->bbat_vchg_microvolts);
+
+ rpi_rtc_set_charge_voltage(dev);
+
+ return devm_rtc_register_device(vrtc->rtc);
+}
+
+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");
\ No newline at end of file
--
2.55.0
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