[PATCH 4/4] regulator: Add support for UGREEN NASync DH2300 MCU SATA power gate

[Alexey Charkov]

Add a driver for the SATA drive-bay power gate function of the UGREEN
NASync DH2300 embedded controller (HC32F005 MCU).

This is a simple on/off regulator, controlled by bit 0 of register 0x41,
with inverted polarity (0 = enabled, 1 = disabled). Boot-time default is
disabled, so this driver is required to use the NAS functionality.

Signed-off-by: Alexey Charkov <alchark at flipper.net>
---
 MAINTAINERS                                     |  1 +
 drivers/regulator/Kconfig                       | 12 ++++
 drivers/regulator/Makefile                      |  1 +
 drivers/regulator/ugreen-dh2300-mcu-regulator.c | 80 +++++++++++++++++++++++++
 4 files changed, 94 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 9578a06fe651..2fc84be86e46 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27638,6 +27638,7 @@ 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
+F:	drivers/regulator/ugreen-dh2300-mcu-regulator.c
 
 UHID USERSPACE HID IO DRIVER
 M:	David Rheinsberg <david at readahead.eu>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index a54a549196fe..e692ff864806 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -1812,6 +1812,18 @@ config REGULATOR_TWL4030
 	  This driver supports the voltage regulators provided by
 	  this family of companion chips.
 
+config REGULATOR_UGREEN_DH2300_MCU
+	tristate "UGREEN NASync DH2300 MCU SATA power regulator"
+	depends on MFD_UGREEN_DH2300_MCU
+	help
+	  Say yes here to enable support for the SATA drive-bay power gate of
+	  the UGREEN NASync DH2300 embedded controller. The regulator is a
+	  sub-device of the ugreen-dh2300-mcu MFD core and is normally consumed
+	  by the SATA controllers via their target-supply.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ugreen-dh2300-mcu-regulator.
+
 config REGULATOR_UNIPHIER
 	tristate "UniPhier regulator driver"
 	depends on ARCH_UNIPHIER || COMPILE_TEST
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index 134eee274dbf..44956d795923 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -206,6 +206,7 @@ obj-$(CONFIG_REGULATOR_TPS6594) += tps6594-regulator.o
 obj-$(CONFIG_REGULATOR_TPS65132) += tps65132-regulator.o
 obj-$(CONFIG_REGULATOR_TPS68470) += tps68470-regulator.o
 obj-$(CONFIG_REGULATOR_TWL4030) += twl-regulator.o twl6030-regulator.o
+obj-$(CONFIG_REGULATOR_UGREEN_DH2300_MCU) += ugreen-dh2300-mcu-regulator.o
 obj-$(CONFIG_REGULATOR_UNIPHIER) += uniphier-regulator.o
 obj-$(CONFIG_REGULATOR_RZG2L_VBCTRL) += renesas-usb-vbus-regulator.o
 obj-$(CONFIG_REGULATOR_VCTRL) += vctrl-regulator.o
diff --git a/drivers/regulator/ugreen-dh2300-mcu-regulator.c b/drivers/regulator/ugreen-dh2300-mcu-regulator.c
new file mode 100644
index 000000000000..69fda90f7ace
--- /dev/null
+++ b/drivers/regulator/ugreen-dh2300-mcu-regulator.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SATA drive-bay power gate for the UGREEN NASync DH2300 embedded controller
+ * (HC32F005 MCU).
+ *
+ * The microcontroller gates the SATA bay power rail through register 0x41.
+ * The polarity is inverted: writing 0 enables the rail, writing 1 disables it
+ * (the controller latches "off" out of reset).
+ */
+
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+#define UGREEN_DH2300_MCU_REG_SATA_POWER	0x41
+
+static const struct regulator_ops ugreen_dh2300_sata_ops = {
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+};
+
+static const struct regulator_desc ugreen_dh2300_sata_desc = {
+	.name = "sata-power",
+	.enable_is_inverted = true,
+	.enable_mask = 0x01,
+	.enable_reg = UGREEN_DH2300_MCU_REG_SATA_POWER,
+	.supply_name = "vin",
+	.ops = &ugreen_dh2300_sata_ops,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+};
+
+static int ugreen_dh2300_mcu_regulator_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regulator_config config = { };
+	struct regulator_dev *rdev;
+	struct device_node *np;
+
+	np = of_get_child_by_name(dev->parent->of_node, "regulator");
+	if (!np)
+		return dev_err_probe(dev, -ENODEV,
+				     "missing regulator child node\n");
+
+	config.dev = dev;
+	config.of_node = np;
+	config.regmap = dev_get_regmap(dev->parent, NULL);
+	if (!config.regmap) {
+		of_node_put(np);
+		return dev_err_probe(dev, -ENODEV,
+				     "no regmap available from parent\n");
+	}
+
+	config.init_data = of_get_regulator_init_data(dev, np,
+						      &ugreen_dh2300_sata_desc);
+
+	rdev = devm_regulator_register(dev, &ugreen_dh2300_sata_desc, &config);
+	of_node_put(np);
+	if (IS_ERR(rdev))
+		return dev_err_probe(dev, PTR_ERR(rdev),
+				     "failed to register regulator\n");
+
+	return 0;
+}
+
+static struct platform_driver ugreen_dh2300_mcu_regulator_driver = {
+	.driver = {
+		.name = "ugreen-dh2300-mcu-regulator",
+	},
+	.probe = ugreen_dh2300_mcu_regulator_probe,
+};
+module_platform_driver(ugreen_dh2300_mcu_regulator_driver);
+
+MODULE_DESCRIPTION("UGREEN NASync DH2300 MCU SATA power regulator");
+MODULE_LICENSE("GPL");

-- 
2.53.0