reboot-mode: read the boot mode from RTC memory

RTC devices could provide battery-backed memory that can be used for
storing the reboot mode magic value.

Add a new reboot-mode back-end that uses RTC to store the reboot-mode
magic value. The driver also supports both endianness modes.

Signed-off-by: Nandor Han <nandor.han@vaisala.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

3 files changed, 137 insertions, 0 deletions

diff --git a/drivers/reboot-mode/Kconfig b/drivers/reboot-mode/Kconfig
index ff65e2031a..ac67bfcef6 100644
--- a/drivers/reboot-mode/Kconfig
+++ b/drivers/reboot-mode/Kconfig
@@ -24,4 +24,13 @@ config DM_REBOOT_MODE_GPIO
 		a device in a specific mode by using a GPIO that can be controlled
 		outside U-Boot.
 
+config DM_REBOOT_MODE_RTC
+	bool "Use RTC as reboot mode backend"
+	depends on DM_REBOOT_MODE
+	default n
+	help
+		Use RTC non volatile memory to control the reboot mode. This will allow users to boot
+		a device in a specific mode by using a register(s) that can be controlled
+		outside U-Boot (e.g. Kernel).
+
 endmenu
diff --git a/drivers/reboot-mode/Makefile b/drivers/reboot-mode/Makefile
index 04917be4f4..2c13780ced 100644
--- a/drivers/reboot-mode/Makefile
+++ b/drivers/reboot-mode/Makefile
@@ -6,3 +6,4 @@
 
 obj-$(CONFIG_DM_REBOOT_MODE) += reboot-mode-uclass.o
 obj-$(CONFIG_DM_REBOOT_MODE_GPIO) += reboot-mode-gpio.o
+obj-$(CONFIG_DM_REBOOT_MODE_RTC) += reboot-mode-rtc.o
diff --git a/drivers/reboot-mode/reboot-mode-rtc.c b/drivers/reboot-mode/reboot-mode-rtc.c
new file mode 100644
index 0000000000..972d0cdbcb
--- /dev/null
+++ b/drivers/reboot-mode/reboot-mode-rtc.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c), Vaisala Oyj
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <reboot-mode/reboot-mode-rtc.h>
+#include <reboot-mode/reboot-mode.h>
+#include <rtc.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static int reboot_mode_get(struct udevice *dev, u32 *buf)
+{
+	if (!buf)
+		return -EINVAL;
+
+	int ret;
+	u8 *val = (u8 *)buf;
+	struct reboot_mode_rtc_platdata *plat_data;
+
+	plat_data = dev_get_plat(dev);
+	if (!plat_data)
+		return -EINVAL;
+
+	for (int i = 0; i < plat_data->size; i++) {
+		ret = rtc_read8(plat_data->rtc, plat_data->addr + i);
+		if (ret < 0)
+			return ret;
+
+		val[i] = ret;
+	}
+
+	if (plat_data->is_big_endian)
+		*buf = __be32_to_cpu(*buf);
+	else
+		*buf = __le32_to_cpu(*buf);
+
+	return 0;
+}
+
+static int reboot_mode_set(struct udevice *dev, u32 buf)
+{
+	int ret;
+	u8 *val;
+	struct reboot_mode_rtc_platdata *plat_data;
+
+	plat_data = dev_get_plat(dev);
+	if (!plat_data)
+		return -EINVAL;
+
+	if (plat_data->is_big_endian)
+		buf = __cpu_to_be32(buf);
+	else
+		buf = __cpu_to_le32(buf);
+
+	val = (u8 *)&buf;
+
+	for (int i = 0; i < plat_data->size; i++) {
+		ret = rtc_write8(plat_data->rtc, (plat_data->addr + i), val[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+#if CONFIG_IS_ENABLED(OF_CONTROL)
+static int reboot_mode_ofdata_to_platdata(struct udevice *dev)
+{
+	struct ofnode_phandle_args phandle_args;
+	struct reboot_mode_rtc_platdata *plat_data;
+
+	plat_data = dev_get_plat(dev);
+	if (!plat_data)
+		return -EINVAL;
+
+	if (dev_read_phandle_with_args(dev, "rtc", NULL, 0, 0, &phandle_args)) {
+		dev_err(dev, "RTC device not specified\n");
+		return -ENOENT;
+	}
+
+	if (uclass_get_device_by_ofnode(UCLASS_RTC, phandle_args.node,
+					&plat_data->rtc)) {
+		dev_err(dev, "could not get the RTC device\n");
+		return -ENODEV;
+	}
+
+	plat_data->addr =
+		dev_read_addr_size_index(dev, 0, (fdt_size_t *)&plat_data->size);
+	if (plat_data->addr == FDT_ADDR_T_NONE) {
+		dev_err(dev, "Invalid RTC address\n");
+		return -EINVAL;
+	}
+	if (plat_data->size > sizeof(u32)) {
+		dev_err(dev, "Invalid reg size\n");
+		return -EINVAL;
+	}
+
+	plat_data->is_big_endian = ofnode_read_bool(dev_ofnode(dev), "big-endian");
+
+	return 0;
+}
+
+static const struct udevice_id reboot_mode_ids[] = {
+	{ .compatible = "reboot-mode-rtc", 0 },
+	{}
+};
+#endif
+
+static const struct reboot_mode_ops reboot_mode_rtc_ops = {
+	.get = reboot_mode_get,
+	.set = reboot_mode_set,
+};
+
+U_BOOT_DRIVER(reboot_mode_rtc) = {
+	.name = "reboot-mode-rtc",
+	.id = UCLASS_REBOOT_MODE,
+#if CONFIG_IS_ENABLED(OF_CONTROL)
+	.of_match = reboot_mode_ids,
+	.of_to_plat = reboot_mode_ofdata_to_platdata,
+#endif
+	.plat_auto = sizeof(struct reboot_mode_rtc_platdata),
+	.ops = &reboot_mode_rtc_ops,
+};