regulator: add support for SY8106A regulator

SY8106A is an I2C attached single output regulator made by Silergy Corp,
which is used on several Allwinner H3/H5 SBCs to control the power
supply of the ARM cores.

Add a driver for it.

Signed-off-by: Ondrej Jirman <megous@megous.com>
[Icenowy: Change commit message, remove enable/disable code, add default
 ramp_delay, add comment for go bit, add code for fixed mode voltage]
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

4 files changed, 181 insertions, 1 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 0a1410d5a621..971300930067 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13461,6 +13461,12 @@ S:	Supported
 F:      net/switchdev/
 F:      include/net/switchdev.h
 
+SY8106A REGULATOR DRIVER
+M:      Icenowy Zheng <icenowy@aosc.io>
+S:      Maintained
+F:      drivers/regulator/sy8106a-regulator.c
+F:      Documentation/devicetree/bindings/regulator/sy8106a-regulator.txt
+
 SYNC FILE FRAMEWORK
 M:      Sumit Semwal <sumit.semwal@linaro.org>
 R:      Gustavo Padovan <gustavo@padovan.org>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 097f61784a7d..4efae3b7e746 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -801,6 +801,13 @@ config REGULATOR_STW481X_VMMC
           This driver supports the internal VMMC regulator in the STw481x
           PMIC chips.
 
+config REGULATOR_SY8106A
+        tristate "Silergy SY8106A regulator"
+        depends on I2C && (OF || COMPILE_TEST)
+        select REGMAP_I2C
+        help
+          This driver supports SY8106A single output regulator.
+
 config REGULATOR_TPS51632
         tristate "TI TPS51632 Power Regulator"
         depends on I2C
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index 590674fbecd7..d81fb02bd6e9 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -100,6 +100,7 @@ obj-$(CONFIG_REGULATOR_SC2731) += sc2731-regulator.o
 obj-$(CONFIG_REGULATOR_SKY81452) += sky81452-regulator.o
 obj-$(CONFIG_REGULATOR_STM32_VREFBUF) += stm32-vrefbuf.o
 obj-$(CONFIG_REGULATOR_STW481X_VMMC) += stw481x-vmmc.o
+obj-$(CONFIG_REGULATOR_SY8106A) += sy8106a-regulator.o
 obj-$(CONFIG_REGULATOR_TI_ABB) += ti-abb-regulator.o
 obj-$(CONFIG_REGULATOR_TPS6105X) += tps6105x-regulator.o
 obj-$(CONFIG_REGULATOR_TPS62360) += tps62360-regulator.o
@@ -125,5 +126,4 @@ obj-$(CONFIG_REGULATOR_WM8350) += wm8350-regulator.o
 obj-$(CONFIG_REGULATOR_WM8400) += wm8400-regulator.o
 obj-$(CONFIG_REGULATOR_WM8994) += wm8994-regulator.o
 
-
 ccflags-$(CONFIG_REGULATOR_DEBUG) += -DDEBUG
diff --git a/drivers/regulator/sy8106a-regulator.c b/drivers/regulator/sy8106a-regulator.c
new file mode 100644
index 000000000000..65fbd1f0b612
--- /dev/null
+++ b/drivers/regulator/sy8106a-regulator.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// sy8106a-regulator.c - Regulator device driver for SY8106A
+//
+// Copyright (C) 2016 Ondřej Jirman <megous@megous.com>
+// Copyright (c) 2017-2018 Icenowy Zheng <icenowy@aosc.io>
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+#define SY8106A_REG_VOUT1_SEL           0x01
+#define SY8106A_REG_VOUT_COM            0x02
+#define SY8106A_REG_VOUT1_SEL_MASK      0x7f
+#define SY8106A_DISABLE_REG             BIT(0)
+/*
+ * The I2C controlled voltage will only work when this bit is set; otherwise
+ * it will behave like a fixed regulator.
+ */
+#define SY8106A_GO_BIT                  BIT(7)
+
+struct sy8106a {
+        struct regulator_dev *rdev;
+        struct regmap *regmap;
+        u32 fixed_voltage;
+};
+
+static const struct regmap_config sy8106a_regmap_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+};
+
+static const struct regulator_ops sy8106a_ops = {
+        .set_voltage_sel = regulator_set_voltage_sel_regmap,
+        .set_voltage_time_sel = regulator_set_voltage_time_sel,
+        .get_voltage_sel = regulator_get_voltage_sel_regmap,
+        .list_voltage = regulator_list_voltage_linear,
+        /* Enabling/disabling the regulator is not yet implemented */
+};
+
+/* Default limits measured in millivolts */
+#define SY8106A_MIN_MV          680
+#define SY8106A_MAX_MV          1950
+#define SY8106A_STEP_MV         10
+
+static const struct regulator_desc sy8106a_reg = {
+        .name = "SY8106A",
+        .id = 0,
+        .ops = &sy8106a_ops,
+        .type = REGULATOR_VOLTAGE,
+        .n_voltages = ((SY8106A_MAX_MV - SY8106A_MIN_MV) / SY8106A_STEP_MV) + 1,
+        .min_uV = (SY8106A_MIN_MV * 1000),
+        .uV_step = (SY8106A_STEP_MV * 1000),
+        .vsel_reg = SY8106A_REG_VOUT1_SEL,
+        .vsel_mask = SY8106A_REG_VOUT1_SEL_MASK,
+        /*
+         * This ramp_delay is a conservative default value which works on
+         * H3/H5 boards VDD-CPUX situations.
+         */
+        .ramp_delay = 200,
+        .owner = THIS_MODULE,
+};
+
+/*
+ * I2C driver interface functions
+ */
+static int sy8106a_i2c_probe(struct i2c_client *i2c,
+                            const struct i2c_device_id *id)
+{
+        struct sy8106a *chip;
+        struct device *dev = &i2c->dev;
+        struct regulator_dev *rdev = NULL;
+        struct regulator_config config = { };
+        unsigned int reg, vsel;
+        int error;
+
+        chip = devm_kzalloc(&i2c->dev, sizeof(struct sy8106a), GFP_KERNEL);
+        if (!chip)
+                return -ENOMEM;
+
+        error = of_property_read_u32(dev->of_node, "silergy,fixed-microvolt",
+                                     &chip->fixed_voltage);
+        if (error)
+                return error;
+
+        if (chip->fixed_voltage < SY8106A_MIN_MV * 1000 ||
+            chip->fixed_voltage > SY8106A_MAX_MV * 1000)
+                return -EINVAL;
+
+        chip->regmap = devm_regmap_init_i2c(i2c, &sy8106a_regmap_config);
+        if (IS_ERR(chip->regmap)) {
+                error = PTR_ERR(chip->regmap);
+                dev_err(dev, "Failed to allocate register map: %d\n", error);
+                return error;
+        }
+
+        config.dev = &i2c->dev;
+        config.regmap = chip->regmap;
+        config.driver_data = chip;
+
+        config.of_node = dev->of_node;
+        config.init_data = of_get_regulator_init_data(dev, dev->of_node,
+                                                      &sy8106a_reg);
+
+        if (!config.init_data)
+                return -ENOMEM;
+
+        /* Ensure GO_BIT is enabled when probing */
+        error = regmap_read(chip->regmap, SY8106A_REG_VOUT1_SEL, &reg);
+        if (error)
+                return error;
+
+        if (!(reg & SY8106A_GO_BIT)) {
+                vsel = (chip->fixed_voltage / 1000 - SY8106A_MIN_MV) /
+                       SY8106A_STEP_MV;
+
+                error = regmap_write(chip->regmap, SY8106A_REG_VOUT1_SEL,
+                                     vsel | SY8106A_GO_BIT);
+                if (error)
+                        return error;
+        }
+
+        /* Probe regulator */
+        rdev = devm_regulator_register(&i2c->dev, &sy8106a_reg, &config);
+        if (IS_ERR(rdev)) {
+                error = PTR_ERR(rdev);
+                dev_err(&i2c->dev, "Failed to register SY8106A regulator: %d\n", error);
+                return error;
+        }
+
+        chip->rdev = rdev;
+
+        i2c_set_clientdata(i2c, chip);
+
+        return 0;
+}
+
+static const struct of_device_id sy8106a_i2c_of_match[] = {
+        { .compatible = "silergy,sy8106a" },
+        { },
+};
+MODULE_DEVICE_TABLE(of, sy8106a_i2c_of_match);
+
+static const struct i2c_device_id sy8106a_i2c_id[] = {
+        { "sy8106a", 0 },
+        { },
+};
+MODULE_DEVICE_TABLE(i2c, sy8106a_i2c_id);
+
+static struct i2c_driver sy8106a_regulator_driver = {
+        .driver = {
+                .name = "sy8106a",
+                .of_match_table = of_match_ptr(sy8106a_i2c_of_match),
+        },
+        .probe = sy8106a_i2c_probe,
+        .id_table = sy8106a_i2c_id,
+};
+
+module_i2c_driver(sy8106a_regulator_driver);
+
+MODULE_AUTHOR("Ondřej Jirman <megous@megous.com>");
+MODULE_AUTHOR("Icenowy Zheng <icenowy@aosc.io>");
+MODULE_DESCRIPTION("Regulator device driver for Silergy SY8106A");
+MODULE_LICENSE("GPL");