regulator: add driver for stm32-vrefbuf

This driver supports STMicroelectronics STM32 VREFBUF (voltage
reference buffer) which can be used as voltage reference for
internal ADCs, DACs and also for external components through
dedicated Vref+ pin. Ported from Linux v5.11-rc1.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

4 files changed, 255 insertions, 0 deletions

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 1ce057180a..9be81832f2 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -28,6 +28,15 @@ config REGULATOR_STM32_PWR
 	  This driver supports internal regulators (1V1, 1V8, 3V3) in the
 	  STMicroelectronics STM32 chips.
 
+config REGULATOR_STM32_VREFBUF
+	tristate "STMicroelectronics STM32 VREFBUF"
+	depends on ARCH_STM32MP || COMPILE_TEST
+	help
+	  This driver supports STMicroelectronics STM32 VREFBUF (voltage
+	  reference buffer) which can be used as voltage reference for
+	  internal ADCs, DACs and also for external components through
+	  dedicated Vref+ pin.
+
 config REGULATOR_STPMIC1
 	tristate "STMicroelectronics STPMIC1 PMIC Regulators"
 	depends on MFD_STPMIC1
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index 4d0bba6c52..67859bb79e 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_REGULATOR_PFUZE) += pfuze.o
 obj-$(CONFIG_REGULATOR_STPMIC1) += stpmic1_regulator.o
 obj-$(CONFIG_REGULATOR_ANATOP) += anatop-regulator.o
 obj-$(CONFIG_REGULATOR_STM32_PWR) += stm32-pwr.o
+obj-$(CONFIG_REGULATOR_STM32_VREFBUF) += stm32-vrefbuf.o
diff --git a/drivers/regulator/helpers.c b/drivers/regulator/helpers.c
index c4877cecf7..e741944ce7 100644
--- a/drivers/regulator/helpers.c
+++ b/drivers/regulator/helpers.c
@@ -369,4 +369,29 @@ int regulator_map_voltage_iterate(struct regulator_dev *rdev,
 }
 EXPORT_SYMBOL_GPL(regulator_map_voltage_iterate);
 
+/**
+ * regulator_list_voltage_table - List voltages with table based mapping
+ *
+ * @rdev: Regulator device
+ * @selector: Selector to convert into a voltage
+ *
+ * Regulators with table based mapping between voltages and
+ * selectors can set volt_table in the regulator descriptor
+ * and then use this function as their list_voltage() operation.
+ */
+int regulator_list_voltage_table(struct regulator_dev *rdev,
+				 unsigned int selector)
+{
+	if (!rdev->desc->volt_table) {
+		BUG_ON(!rdev->desc->volt_table);
+		return -EINVAL;
+	}
 
+	if (selector >= rdev->desc->n_voltages)
+		return -EINVAL;
+	if (selector < rdev->desc->linear_min_sel)
+		return 0;
+
+	return rdev->desc->volt_table[selector];
+}
+EXPORT_SYMBOL_GPL(regulator_list_voltage_table);
diff --git a/drivers/regulator/stm32-vrefbuf.c b/drivers/regulator/stm32-vrefbuf.c
new file mode 100644
index 0000000000..3956b1f64f
--- /dev/null
+++ b/drivers/regulator/stm32-vrefbuf.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
+ */
+
+#include <common.h>
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/iopoll.h>
+#include <of.h>
+#include <regulator.h>
+
+/* STM32 VREFBUF registers */
+#define STM32_VREFBUF_CSR		0x00
+
+/* STM32 VREFBUF CSR bitfields */
+#define STM32_VRS			GENMASK(6, 4)
+#define STM32_VRR			BIT(3)
+#define STM32_HIZ			BIT(1)
+#define STM32_ENVR			BIT(0)
+
+#define STM32_VREFBUF_AUTO_SUSPEND_DELAY_MS	10
+
+#define readl_relaxed readl
+#define writel_relaxed writel
+
+struct stm32_vrefbuf {
+	void __iomem *base;
+	struct clk *clk;
+	struct device_d *dev;
+	struct regulator_dev rdev;
+};
+
+struct stm32_vrefbuf_desc {
+	struct regulator_desc desc;
+	const char *supply_name;
+};
+
+static inline struct stm32_vrefbuf *to_stm32_vrefbuf(struct regulator_dev *rdev)
+{
+	return container_of(rdev, struct stm32_vrefbuf, rdev);
+}
+
+static const unsigned int stm32_vrefbuf_voltages[] = {
+	/* Matches resp. VRS = 000b, 001b, 010b, 011b */
+	2500000, 2048000, 1800000, 1500000,
+};
+
+static int stm32_vrefbuf_enable(struct regulator_dev *rdev)
+{
+	struct stm32_vrefbuf *priv = to_stm32_vrefbuf(rdev);
+	u32 val;
+	int ret;
+
+	val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+	val = (val & ~STM32_HIZ) | STM32_ENVR;
+	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
+
+	/*
+	 * Vrefbuf startup time depends on external capacitor: wait here for
+	 * VRR to be set. That means output has reached expected value.
+	 * ~650us sleep should be enough for caps up to 1.5uF. Use 10ms as
+	 * arbitrary timeout.
+	 */
+	ret = readl_poll_timeout(priv->base + STM32_VREFBUF_CSR, val,
+				 val & STM32_VRR, 10000);
+	if (ret) {
+		dev_err(priv->dev, "stm32 vrefbuf timed out!\n");
+		val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+		val = (val & ~STM32_ENVR) | STM32_HIZ;
+		writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
+	}
+
+	return ret;
+}
+
+static int stm32_vrefbuf_disable(struct regulator_dev *rdev)
+{
+	struct stm32_vrefbuf *priv = to_stm32_vrefbuf(rdev);
+	u32 val;
+
+	val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+	val &= ~STM32_ENVR;
+	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
+
+	return 0;
+}
+
+static int stm32_vrefbuf_is_enabled(struct regulator_dev *rdev)
+{
+	struct stm32_vrefbuf *priv = to_stm32_vrefbuf(rdev);
+	int ret;
+
+	ret = readl_relaxed(priv->base + STM32_VREFBUF_CSR) & STM32_ENVR;
+
+	return ret;
+}
+
+static int stm32_vrefbuf_set_voltage_sel(struct regulator_dev *rdev,
+					 unsigned sel)
+{
+	struct stm32_vrefbuf *priv = to_stm32_vrefbuf(rdev);
+	u32 val;
+
+	val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+	val = (val & ~STM32_VRS) | FIELD_PREP(STM32_VRS, sel);
+	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
+
+	return 0;
+}
+
+static int stm32_vrefbuf_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct stm32_vrefbuf *priv = to_stm32_vrefbuf(rdev);
+	u32 val;
+	int ret;
+
+	val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+	ret = FIELD_GET(STM32_VRS, val);
+
+	return ret;
+}
+
+static const struct regulator_ops stm32_vrefbuf_volt_ops = {
+	.enable		= stm32_vrefbuf_enable,
+	.disable	= stm32_vrefbuf_disable,
+	.is_enabled	= stm32_vrefbuf_is_enabled,
+	.get_voltage_sel = stm32_vrefbuf_get_voltage_sel,
+	.set_voltage_sel = stm32_vrefbuf_set_voltage_sel,
+	.list_voltage	= regulator_list_voltage_table,
+};
+
+static const struct stm32_vrefbuf_desc stm32_vrefbuf_regu = {
+	.desc = {
+		.volt_table = stm32_vrefbuf_voltages,
+		.n_voltages = ARRAY_SIZE(stm32_vrefbuf_voltages),
+		.ops = &stm32_vrefbuf_volt_ops,
+		.off_on_delay = 1000,
+	},
+	.supply_name = "vdda",
+};
+
+static int stm32_vrefbuf_probe(struct device_d *dev)
+{
+	struct stm32_vrefbuf *priv;
+	struct regulator_dev *rdev;
+	struct regulator *supply;
+	int ret;
+
+	supply = regulator_get(dev, stm32_vrefbuf_regu.supply_name);
+	if (IS_ERR(supply))
+		return PTR_ERR(supply);
+
+	priv = xzalloc(sizeof(*priv));
+	priv->dev = dev;
+
+	priv->base = dev_request_mem_region(dev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->clk = clk_get(dev, NULL);
+	if (IS_ERR(priv->clk))
+		return PTR_ERR(priv->clk);
+
+	ret = clk_enable(priv->clk);
+	if (ret) {
+		dev_err(dev, "clk enable failed with error %d\n", ret);
+		return ret;
+	}
+
+	rdev = &priv->rdev;
+
+	rdev->dev = dev;
+	rdev->desc = &stm32_vrefbuf_regu.desc;
+
+	ret = of_regulator_register(rdev, dev->device_node);
+	if (ret) {
+		ret = PTR_ERR(rdev);
+		dev_err(dev, "register failed with error %d\n", ret);
+		goto err_clk_dis;
+	}
+
+	regulator_enable(supply);
+
+	dev->priv = priv;
+
+	return 0;
+
+err_clk_dis:
+	clk_disable(priv->clk);
+
+	return ret;
+}
+
+static void stm32_vrefbuf_remove(struct device_d *dev)
+{
+	struct stm32_vrefbuf *priv = dev->priv;
+
+	clk_disable(priv->clk);
+};
+
+static const struct of_device_id __maybe_unused stm32_vrefbuf_of_match[] = {
+	{ .compatible = "st,stm32-vrefbuf", },
+	{},
+};
+
+static struct driver_d stm32_vrefbuf_driver = {
+	.probe = stm32_vrefbuf_probe,
+	.name  = "stm32-vrefbuf",
+	.remove = stm32_vrefbuf_remove,
+	.of_compatible = stm32_vrefbuf_of_match,
+};
+device_platform_driver(stm32_vrefbuf_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 VREFBUF driver");
+MODULE_ALIAS("platform:stm32-vrefbuf");