[PATCH 2/6] mfd: spacemit: add support for SpacemiT PMICs

[Alex Elder <elder@riscstar.com>]

Add support for SpacemiT PMICs. Initially only the P1 PMIC is supported
but the driver is structured to allow support for others to be added.

The P1 PMIC is controlled by I2C, and is normally implemented with the
SpacemiT K1 SoC.  This PMIC provides six buck converters and 12 LDO
regulators.  It also implements a switch, watchdog timer, real-time clock,
and more, but initially we will only support its regulators.

Signed-off-by: Alex Elder <elder@riscstar.com>
---
 drivers/mfd/Kconfig         | 11 +++++
 drivers/mfd/Makefile        |  1 +
 drivers/mfd/spacemit-pmic.c | 91 +++++++++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 drivers/mfd/spacemit-pmic.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 6fb3768e3d71c..c59ae6cc2dd8d 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1182,6 +1182,17 @@ config MFD_QCOM_RPM
 	  Say M here if you want to include support for the Qualcomm RPM as a
 	  module. This will build a module called "qcom_rpm".
 
+config MFD_SPACEMIT_PMIC
+	tristate "SpacemiT PMIC"
+	depends on ARCH_SPACEMIT || COMPILE_TEST
+	depends on I2C && OF
+	select MFD_CORE
+	select REGMAP_I2C
+	default ARCH_SPACEMIT
+	help
+	  This option enables support for SpacemiT I2C based PMICs.  At
+	  this time only the P1 PMIC (used with the K1 SoC) is supported.
+
 config MFD_SPMI_PMIC
 	tristate "Qualcomm SPMI PMICs"
 	depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 79495f9f3457b..59d1ec8db3a3f 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -266,6 +266,7 @@ obj-$(CONFIG_MFD_SUN4I_GPADC)	+= sun4i-gpadc.o
 obj-$(CONFIG_MFD_STM32_LPTIMER)	+= stm32-lptimer.o
 obj-$(CONFIG_MFD_STM32_TIMERS) 	+= stm32-timers.o
 obj-$(CONFIG_MFD_MXS_LRADC)     += mxs-lradc.o
+obj-$(CONFIG_MFD_SPACEMIT_PMIC)	+= spacemit-pmic.o
 obj-$(CONFIG_MFD_SC27XX_PMIC)	+= sprd-sc27xx-spi.o
 obj-$(CONFIG_RAVE_SP_CORE)	+= rave-sp.o
 obj-$(CONFIG_MFD_ROHM_BD71828)	+= rohm-bd71828.o
diff --git a/drivers/mfd/spacemit-pmic.c b/drivers/mfd/spacemit-pmic.c
new file mode 100644
index 0000000000000..7c3c3e27236da
--- /dev/null
+++ b/drivers/mfd/spacemit-pmic.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 by RISCstar Solutions Corporation.  All rights reserved.
+ * Derived from code from:
+ *	Copyright (C) 2024 Troy Mitchell <troymitchell988@gmail.com>
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct spacemit_pmic_data {
+	const struct regmap_config *regmap_config;
+	const struct mfd_cell *mfd_cells;	/* array */
+	size_t mfd_cell_count;
+};
+
+static const struct regmap_config p1_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.max_register	= 0xaa,
+};
+
+/* The name field defines the *driver* name that should bind to the device */
+static const struct mfd_cell p1_cells[] = {
+	{
+		.name		= "spacemit-p1-regulator",
+	},
+};
+
+static const struct spacemit_pmic_data p1_pmic_data = {
+	.regmap_config	= &p1_regmap_config,
+	.mfd_cells	= p1_cells,
+	.mfd_cell_count	= ARRAY_SIZE(p1_cells),
+};
+
+static int spacemit_pmic_probe(struct i2c_client *client)
+{
+	const struct spacemit_pmic_data *data;
+	struct device *dev = &client->dev;
+	struct regmap *regmap;
+
+	/* We currently have no need for a device-specific structure */
+	data = of_device_get_match_data(dev);
+	regmap = devm_regmap_init_i2c(client, data->regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "regmap initialization failed");
+
+	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+				    data->mfd_cells, data->mfd_cell_count,
+				    NULL, 0, NULL);
+}
+
+static const struct of_device_id spacemit_pmic_match[] = {
+	{
+		.compatible	= "spacemit,p1",
+		.data		= &p1_pmic_data,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, spacemit_pmic_match);
+
+static struct i2c_driver spacemit_pmic_i2c_driver = {
+	.driver = {
+		.name = "spacemit-pmic",
+		.of_match_table = spacemit_pmic_match,
+	},
+	.probe    = spacemit_pmic_probe,
+};
+
+static int __init spacemit_pmic_init(void)
+{
+	return i2c_add_driver(&spacemit_pmic_i2c_driver);
+}
+
+static void __exit spacemit_pmic_exit(void)
+{
+	i2c_del_driver(&spacemit_pmic_i2c_driver);
+}
+
+module_init(spacemit_pmic_init);
+module_exit(spacemit_pmic_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("SpacemiT multi-function PMIC driver");
-- 
2.45.2