regulator: sun20i: Add Allwinner D1 LDOs driver

D1 contains two pairs of LDOs, "analog" LDOs and "system" LDOs. They are
similar and can share a driver, but only the system LDOs have a DT
binding defined so far.

The system LDOs have a single linear range. The voltage step is not an
integer, so a custom .list_voltage is needed to get the rounding right.

Signed-off-by: Samuel Holland <[e-mail]>
Reviewed-by: Andre Przywara <[e-mail]>
Reviewed-by: Jernej Skrabec <[e-mail]>
Signed-off-by: Chen-Yu Tsai <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/Kconfig

···
 	  This driver supports the internal VMMC regulator in the STw481x
 	  PMIC chips.
 
+config REGULATOR_SUN20I
+	tristate "Allwinner D1 internal LDOs"
+	depends on ARCH_SUNXI || COMPILE_TEST
+	select MFD_SYSCON
+	default ARCH_SUNXI
+	help
+	  This driver supports the internal LDOs in the Allwinner D1 SoC.
+
 config REGULATOR_SY7636A
 	tristate "Silergy SY7636A voltage regulator"
 	depends on MFD_SY7636A

drivers/regulator/Makefile

···
 obj-$(CONFIG_REGULATOR_STM32_PWR) += stm32-pwr.o
 obj-$(CONFIG_REGULATOR_STPMIC1) += stpmic1_regulator.o
 obj-$(CONFIG_REGULATOR_STW481X_VMMC) += stw481x-vmmc.o
+obj-$(CONFIG_REGULATOR_SUN20I) += sun20i-regulator.o
 obj-$(CONFIG_REGULATOR_SY7636A) += sy7636a-regulator.o
 obj-$(CONFIG_REGULATOR_SY8106A) += sy8106a-regulator.o
 obj-$(CONFIG_REGULATOR_SY8824X) += sy8824x.o

drivers/regulator/sun20i-regulator.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright (c) 2021-2022 Samuel Holland <[e-mail]>
+//
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+
+#define SUN20I_SYS_LDO_CTRL_REG		0x150
+
+struct sun20i_regulator_data {
+	const struct regulator_desc	*descs;
+	unsigned int			ndescs;
+};
+
+/* regulator_list_voltage_linear() modified for the non-integral uV_step. */
+static int sun20i_d1_system_ldo_list_voltage(struct regulator_dev *rdev,
+					     unsigned int selector)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	unsigned int fraction, uV;
+
+	if (selector >= desc->n_voltages)
+		return -EINVAL;
+
+	uV = desc->min_uV + (desc->uV_step * selector);
+	fraction = selector + (desc->min_uV % 4);
+
+	if (uV > 1606667)
+		uV += 6667;
+	else
+		fraction++;
+
+	/* Produce correctly-rounded absolute voltages. */
+	return uV + (fraction / 3);
+}
+
+static const struct regulator_ops sun20i_d1_system_ldo_ops = {
+	.list_voltage		= sun20i_d1_system_ldo_list_voltage,
+	.map_voltage		= regulator_map_voltage_ascend,
+	.set_voltage_sel	= regulator_set_voltage_sel_regmap,
+	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
+};
+
+static const struct regulator_desc sun20i_d1_system_ldo_descs[] = {
+	{
+		.name		= "ldoa",
+		.supply_name	= "ldo-in",
+		.of_match	= "ldoa",
+		.ops		= &sun20i_d1_system_ldo_ops,
+		.type		= REGULATOR_VOLTAGE,
+		.owner		= THIS_MODULE,
+		.n_voltages	= 32,
+		.min_uV		= 1593333,
+		.uV_step	= 13333, /* repeating */
+		.vsel_reg	= SUN20I_SYS_LDO_CTRL_REG,
+		.vsel_mask	= GENMASK(7, 0),
+	},
+	{
+		.name		= "ldob",
+		.supply_name	= "ldo-in",
+		.of_match	= "ldob",
+		.ops		= &sun20i_d1_system_ldo_ops,
+		.type		= REGULATOR_VOLTAGE,
+		.owner		= THIS_MODULE,
+		.n_voltages	= 64,
+		.min_uV		= 1166666,
+		.uV_step	= 13333, /* repeating */
+		.vsel_reg	= SUN20I_SYS_LDO_CTRL_REG,
+		.vsel_mask	= GENMASK(15, 8),
+	},
+};
+
+static const struct sun20i_regulator_data sun20i_d1_system_ldos = {
+	.descs	= sun20i_d1_system_ldo_descs,
+	.ndescs	= ARRAY_SIZE(sun20i_d1_system_ldo_descs),
+};
+
+static struct regmap *sun20i_regulator_get_regmap(struct device *dev)
+{
+	struct regmap *regmap;
+
+	/*
+	 * First try the syscon interface. The system control device is not
+	 * compatible with "syscon", so fall back to getting the regmap from
+	 * its platform device. This is ugly, but required for devicetree
+	 * backward compatibility.
+	 */
+	regmap = syscon_node_to_regmap(dev->parent->of_node);
+	if (!IS_ERR(regmap))
+		return regmap;
+
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (regmap)
+		return regmap;
+
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+static int sun20i_regulator_probe(struct platform_device *pdev)
+{
+	const struct sun20i_regulator_data *data;
+	struct device *dev = &pdev->dev;
+	struct regulator_config config;
+	struct regmap *regmap;
+
+	data = of_device_get_match_data(dev);
+	if (!data)
+		return -EINVAL;
+
+	regmap = sun20i_regulator_get_regmap(dev);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap), "Failed to get regmap\n");
+
+	config = (struct regulator_config) {
+		.dev	= dev,
+		.regmap	= regmap,
+	};
+
+	for (unsigned int i = 0; i < data->ndescs; ++i) {
+		const struct regulator_desc *desc = &data->descs[i];
+		struct regulator_dev *rdev;
+
+		rdev = devm_regulator_register(dev, desc, &config);
+		if (IS_ERR(rdev))
+			return PTR_ERR(rdev);
+	}
+
+	return 0;
+}
+
+static const struct of_device_id sun20i_regulator_of_match[] = {
+	{
+		.compatible = "allwinner,sun20i-d1-system-ldos",
+		.data = &sun20i_d1_system_ldos,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, sun20i_regulator_of_match);
+
+static struct platform_driver sun20i_regulator_driver = {
+	.probe	= sun20i_regulator_probe,
+	.driver	= {
+		.name		= "sun20i-regulator",
+		.of_match_table	= sun20i_regulator_of_match,
+	},
+};
+module_platform_driver(sun20i_regulator_driver);
+
+MODULE_AUTHOR("Samuel Holland <[e-mail]>");
+MODULE_DESCRIPTION("Allwinner D1 internal LDO driver");
+MODULE_LICENSE("GPL");