[PATCH 3/4] mfd: Add support for UGREEN NASync DH2300 MCU

[Alexey Charkov]

Add a driver for the HC32F005 MCU used as an embedded controller on the
UGREEN NASync DH2300 NAS.

This part provides the shared I2C regmap to be used by function-specific
sub-devices, and instantiates the SATA drive-bay power gate regulator.
Implemented as an MFD to allow for other functions of the MCU to be added
later: vendor binaries imply that it also provides a hardware watchdog
and somehow serves as a wake source, but so far only the SATA power gating
function has been confirmed in absence of documentation and sources for the
vendor firmware.

Signed-off-by: Alexey Charkov <alchark at flipper.net>
---
 MAINTAINERS                     |  1 +
 drivers/mfd/Kconfig             | 16 +++++++++++
 drivers/mfd/Makefile            |  1 +
 drivers/mfd/ugreen-dh2300-mcu.c | 60 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 78 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index ca27df7cd684..9578a06fe651 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27637,6 +27637,7 @@ UGREEN DH2300 MCU MFD DRIVER
 M:	Alexey Charkov <alchark at flipper.net>
 S:	Maintained
 F:	Documentation/devicetree/bindings/mfd/ugreen,dh2300-mcu.yaml
+F:	drivers/mfd/ugreen-dh2300-mcu.c
 
 UHID USERSPACE HID IO DRIVER
 M:	David Rheinsberg <david at readahead.eu>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 763ce6a34782..5a2ad75bd9c9 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1947,6 +1947,22 @@ config MFD_TPS6594_SPI
 	  This driver can also be built as a module.  If so, the module
 	  will be called tps6594-spi.
 
+config MFD_UGREEN_DH2300_MCU
+	tristate "UGREEN NASync DH2300 embedded controller"
+	depends on I2C
+	depends on OF
+	select MFD_CORE
+	select REGMAP_I2C
+	help
+	  Say yes here to enable support for the HC32F005 microcontroller found
+	  on the UGREEN NASync DH2300 NAS, where it acts as a board embedded
+	  controller. This core driver sets up the shared register map and
+	  instantiates the function sub-devices (the SATA drive-bay power
+	  regulator).
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ugreen-dh2300-mcu.
+
 config TWL4030_CORE
 	bool "TI TWL4030/TWL5030/TWL6030/TPS659x0 Support"
 	depends on I2C=y
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index dd4bb7e77c33..6247239bcfe1 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -109,6 +109,7 @@ obj-$(CONFIG_MFD_TPS65912_SPI)  += tps65912-spi.o
 obj-$(CONFIG_MFD_TPS6594)	+= tps6594-core.o
 obj-$(CONFIG_MFD_TPS6594_I2C)	+= tps6594-i2c.o
 obj-$(CONFIG_MFD_TPS6594_SPI)	+= tps6594-spi.o
+obj-$(CONFIG_MFD_UGREEN_DH2300_MCU)	+= ugreen-dh2300-mcu.o
 obj-$(CONFIG_MENELAUS)		+= menelaus.o
 
 obj-$(CONFIG_TWL4030_CORE)	+= twl-core.o twl4030-irq.o twl6030-irq.o
diff --git a/drivers/mfd/ugreen-dh2300-mcu.c b/drivers/mfd/ugreen-dh2300-mcu.c
new file mode 100644
index 000000000000..5184b0c98759
--- /dev/null
+++ b/drivers/mfd/ugreen-dh2300-mcu.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Core driver for the UGREEN NASync DH2300 embedded controller (HC32F005 MCU).
+ *
+ * The microcontroller sits on I2C and exposes an 8-bit register map. It is a
+ * multi-function device: SATA drive-bay power gate, hardware watchdog and
+ * possibly other functions
+ */
+
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define UGREEN_DH2300_MCU_REG_MAX	0x94
+
+static const struct regmap_config ugreen_dh2300_mcu_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = UGREEN_DH2300_MCU_REG_MAX,
+};
+
+static const struct mfd_cell ugreen_dh2300_mcu_cells[] = {
+	{ .name = "ugreen-dh2300-mcu-regulator" },
+};
+
+static int ugreen_dh2300_mcu_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(client, &ugreen_dh2300_mcu_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "failed to initialise regmap\n");
+
+	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+				    ugreen_dh2300_mcu_cells,
+				    ARRAY_SIZE(ugreen_dh2300_mcu_cells),
+				    NULL, 0, NULL);
+}
+
+static const struct of_device_id ugreen_dh2300_mcu_of_match[] = {
+	{ .compatible = "ugreen,dh2300-mcu" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ugreen_dh2300_mcu_of_match);
+
+static struct i2c_driver ugreen_dh2300_mcu_driver = {
+	.driver = {
+		.name = "ugreen-dh2300-mcu",
+		.of_match_table = ugreen_dh2300_mcu_of_match,
+	},
+	.probe = ugreen_dh2300_mcu_probe,
+};
+module_i2c_driver(ugreen_dh2300_mcu_driver);
+
+MODULE_DESCRIPTION("UGREEN NASync DH2300 embedded controller core driver");
+MODULE_LICENSE("GPL");

-- 
2.53.0