[PATCH v13 2/3] soc: sophgo: cv1800: rtcsys: New driver (handling RTC only)

[Alexander Sverdlin <alexander.sverdlin@gmail.com>]

Add driver for Sophgo CV1800 series SoC RTC subsystem. The RTC module
comprises a 32kHz oscillator, Power-on-Reset (PoR) sub-module, HW state
machine to control chip power-on, power-off and reset. Furthermore, the
8051 subsystem is located within RTCSYS including associated SRAM block.

This patch only populates RTC sub-device.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
---
Changelog:
v13:
- Moved the driver from MFD into SOC subsystem
- Dropped unused "cv1800_rtcsys_rtc_subdev"
v12:
- new patch

 MAINTAINERS                        |  1 +
 drivers/soc/Kconfig                |  1 +
 drivers/soc/Makefile               |  1 +
 drivers/soc/sophgo/Kconfig         | 24 ++++++++++++
 drivers/soc/sophgo/Makefile        |  3 ++
 drivers/soc/sophgo/cv1800-rtcsys.c | 63 ++++++++++++++++++++++++++++++
 6 files changed, 93 insertions(+)
 create mode 100644 drivers/soc/sophgo/Kconfig
 create mode 100644 drivers/soc/sophgo/Makefile
 create mode 100644 drivers/soc/sophgo/cv1800-rtcsys.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 3eee238c2ea2..ac15e448fffb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22354,6 +22354,7 @@ L:	sophgo@lists.linux.dev
 W:	https://github.com/sophgo/linux/wiki
 T:	git https://github.com/sophgo/linux.git
 S:	Maintained
+F:	drivers/soc/sophgo/cv1800-rtcsys.c
 N:	sophgo
 K:	sophgo
 
diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index 6a8daeb8c4b9..11e2383c0654 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -23,6 +23,7 @@ source "drivers/soc/qcom/Kconfig"
 source "drivers/soc/renesas/Kconfig"
 source "drivers/soc/rockchip/Kconfig"
 source "drivers/soc/samsung/Kconfig"
+source "drivers/soc/sophgo/Kconfig"
 source "drivers/soc/sunxi/Kconfig"
 source "drivers/soc/tegra/Kconfig"
 source "drivers/soc/ti/Kconfig"
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 2037a8695cb2..0381a0abdec8 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -29,6 +29,7 @@ obj-y				+= qcom/
 obj-y				+= renesas/
 obj-y				+= rockchip/
 obj-$(CONFIG_SOC_SAMSUNG)	+= samsung/
+obj-y				+= sophgo/
 obj-y				+= sunxi/
 obj-$(CONFIG_ARCH_TEGRA)	+= tegra/
 obj-y				+= ti/
diff --git a/drivers/soc/sophgo/Kconfig b/drivers/soc/sophgo/Kconfig
new file mode 100644
index 000000000000..e50666e423a9
--- /dev/null
+++ b/drivers/soc/sophgo/Kconfig
@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Sophgo/Cvitek SoC drivers
+#
+
+if ARCH_SOPHGO || COMPILE_TEST
+menu "Sophgo/Cvitek SoC drivers"
+
+config SOPHGO_CV1800_RTCSYS
+	tristate "Sophgo CV1800 RTC MFD"
+	default y if COMPILE_TEST
+	select MFD_CORE
+	help
+	  If you say yes here you get support the RTC MFD driver for Sophgo
+	  CV1800 series SoC. The RTC module comprises a 32kHz oscillator,
+	  Power-on-Reset (PoR) sub-module, HW state machine to control chip
+	  power-on, power-off and reset. Furthermore, the 8051 subsystem is
+	  located within RTCSYS including associated SRAM block.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called cv1800-rtcsys.
+
+endmenu
+endif
diff --git a/drivers/soc/sophgo/Makefile b/drivers/soc/sophgo/Makefile
new file mode 100644
index 000000000000..8f22b4e79311
--- /dev/null
+++ b/drivers/soc/sophgo/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_SOPHGO_CV1800_RTCSYS)	+= cv1800-rtcsys.o
diff --git a/drivers/soc/sophgo/cv1800-rtcsys.c b/drivers/soc/sophgo/cv1800-rtcsys.c
new file mode 100644
index 000000000000..cb271f02afcc
--- /dev/null
+++ b/drivers/soc/sophgo/cv1800-rtcsys.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Sophgo CV1800 series SoC RTC subsystem
+ *
+ * The RTC module comprises a 32kHz oscillator, Power-on-Reset (PoR) sub-module,
+ * HW state machine to control chip power-on, power-off and reset. Furthermore,
+ * the 8051 subsystem is located within RTCSYS including associated SRAM block.
+ *
+ * Copyright (C) 2025 Alexander Sverdlin <alexander.sverdlin@gmail.com>
+ *
+ */
+
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+
+static struct resource cv1800_rtcsys_irq_resources[] = {
+	DEFINE_RES_IRQ_NAMED(0, "alarm"),
+};
+
+static const struct mfd_cell cv1800_rtcsys_subdev[] = {
+	{
+		.name = "cv1800-rtc",
+		.num_resources = 1,
+		.resources = &cv1800_rtcsys_irq_resources[0],
+	},
+};
+
+static int cv1800_rtcsys_probe(struct platform_device *pdev)
+{
+	int irq;
+
+	irq = platform_get_irq_byname(pdev, "alarm");
+	if (irq < 0)
+		return irq;
+	cv1800_rtcsys_irq_resources[0].start = irq;
+	cv1800_rtcsys_irq_resources[0].end = irq;
+
+	return devm_mfd_add_devices(&pdev->dev, PLATFORM_DEVID_AUTO,
+				    cv1800_rtcsys_subdev,
+				    ARRAY_SIZE(cv1800_rtcsys_subdev),
+				    NULL, 0, NULL);
+}
+
+static const struct of_device_id cv1800_rtcsys_of_match[] = {
+	{ .compatible = "sophgo,cv1800b-rtc" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, cv1800_rtcsys_of_match);
+
+static struct platform_driver cv1800_rtcsys_mfd = {
+	.probe	= cv1800_rtcsys_probe,
+	.driver	= {
+		.name		= "cv1800_rtcsys",
+		.of_match_table	= cv1800_rtcsys_of_match,
+	},
+};
+module_platform_driver(cv1800_rtcsys_mfd);
+
+MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>");
+MODULE_DESCRIPTION("Sophgo CV1800 series SoC RTC subsystem driver");
+MODULE_LICENSE("GPL");
-- 
2.48.1