[PATCH 2/3] regulator: Add support for stm32-vrefbuf

[Fabrice Gasnier]

Add regulator driver for STM32 voltage reference buffer which can be
used as voltage reference for ADCs, DACs and external components through
dedicated VREF+ pin.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
 drivers/regulator/Kconfig         |  12 +++
 drivers/regulator/Makefile        |   1 +
 drivers/regulator/stm32-vrefbuf.c | 215 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 228 insertions(+)
 create mode 100644 drivers/regulator/stm32-vrefbuf.c

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 48db87d..7950283 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -728,6 +728,18 @@ config REGULATOR_SKY81452
 	  This driver can also be built as a module. If so, the module
 	  will be called sky81452-regulator.
 
+config REGULATOR_STM32_VREFBUF
+	tristate "STMicroelectronics STM32 VREFBUF"
+	depends on ARCH_STM32 || 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.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called stm32-vrefbuf.
+
 config REGULATOR_TI_ABB
 	tristate "TI Adaptive Body Bias on-chip LDO"
 	depends on ARCH_OMAP
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index dc3503f..d8caceb 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_REGULATOR_S2MPA01) += s2mpa01.o
 obj-$(CONFIG_REGULATOR_S2MPS11) += s2mps11.o
 obj-$(CONFIG_REGULATOR_S5M8767) += s5m8767.o
 obj-$(CONFIG_REGULATOR_SKY81452) += sky81452-regulator.o
+obj-$(CONFIG_REGULATOR_STM32_VREFBUF) += stm32-vrefbuf.o
 obj-$(CONFIG_REGULATOR_STW481X_VMMC) += stw481x-vmmc.o
 obj-$(CONFIG_REGULATOR_TI_ABB) += ti-abb-regulator.o
 obj-$(CONFIG_REGULATOR_TPS6105X) += tps6105x-regulator.o
diff --git a/drivers/regulator/stm32-vrefbuf.c b/drivers/regulator/stm32-vrefbuf.c
new file mode 100644
index 0000000..a4efa3b
--- /dev/null
+++ b/drivers/regulator/stm32-vrefbuf.c
@@ -0,0 +1,215 @@
+/*
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
+ *
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_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)
+
+struct stm32_vrefbuf {
+	void __iomem *base;
+	struct clk *clk;
+};
+
+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 = rdev_get_drvdata(rdev);
+	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+	int ret;
+
+	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), 650, 10000);
+	if (ret) {
+		dev_err(&rdev->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 = rdev_get_drvdata(rdev);
+	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+
+	val = (val & ~STM32_ENVR) | STM32_HIZ;
+	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
+
+	return 0;
+}
+
+static int stm32_vrefbuf_is_enabled(struct regulator_dev *rdev)
+{
+	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
+
+	return readl_relaxed(priv->base + STM32_VREFBUF_CSR) & STM32_ENVR;
+}
+
+static int stm32_vrefbuf_set_voltage_sel(struct regulator_dev *rdev,
+					 unsigned sel)
+{
+	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
+	u32 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 = rdev_get_drvdata(rdev);
+	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
+
+	return FIELD_GET(STM32_VRS, val);
+}
+
+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 regulator_desc stm32_vrefbuf_regu = {
+	.name = "vref",
+	.supply_name = "vdda",
+	.volt_table = stm32_vrefbuf_voltages,
+	.n_voltages = ARRAY_SIZE(stm32_vrefbuf_voltages),
+	.ops = &stm32_vrefbuf_volt_ops,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+};
+
+static int stm32_vrefbuf_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct stm32_vrefbuf *priv;
+	struct regulator_config config = { };
+	struct regulator_dev *rdev;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(priv->clk))
+		return PTR_ERR(priv->clk);
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "clk prepare failed\n");
+		return ret;
+	}
+
+	config.dev = &pdev->dev;
+	config.driver_data = priv;
+	config.of_node = pdev->dev.of_node;
+	config.init_data = of_get_regulator_init_data(&pdev->dev,
+						      pdev->dev.of_node,
+						      &stm32_vrefbuf_regu);
+
+	rdev = regulator_register(&stm32_vrefbuf_regu, &config);
+	if (IS_ERR(rdev)) {
+		dev_err(&pdev->dev, "vrefbuf register failed\n");
+		ret = PTR_ERR(rdev);
+		goto err_clk_dis;
+	}
+	platform_set_drvdata(pdev, rdev);
+
+	dev_info(&pdev->dev, "STM32 VREFBUF initialized\n");
+
+	return 0;
+
+err_clk_dis:
+	clk_disable_unprepare(priv->clk);
+
+	return ret;
+}
+
+static int stm32_vrefbuf_remove(struct platform_device *pdev)
+{
+	struct regulator_dev *rdev = platform_get_drvdata(pdev);
+	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
+
+	regulator_unregister(rdev);
+	clk_disable_unprepare(priv->clk);
+
+	return 0;
+};
+
+static const struct of_device_id stm32_vrefbuf_of_match[] = {
+	{ .compatible = "st,stm32-vrefbuf", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_vrefbuf_of_match);
+
+static struct platform_driver stm32_vrefbuf_driver = {
+	.probe = stm32_vrefbuf_probe,
+	.remove = stm32_vrefbuf_remove,
+	.driver = {
+		.name  = "stm32-vrefbuf",
+		.of_match_table = of_match_ptr(stm32_vrefbuf_of_match),
+	},
+};
+
+static int __init stm32_vrefbuf_init(void)
+{
+	return platform_driver_register(&stm32_vrefbuf_driver);
+}
+subsys_initcall(stm32_vrefbuf_init);
+
+static void __exit stm32_vrefbuf_exit(void)
+{
+	platform_driver_unregister(&stm32_vrefbuf_driver);
+}
+module_exit(stm32_vrefbuf_exit)
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@xxxxxx>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 VREFBUF driver");
+MODULE_ALIAS("platform:stm32-vrefbuf");
-- 
1.9.1