1 /*
2  * Copyright (C) STMicroelectronics 2017
3  *
4  * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
5  *
6  * License terms:  GNU General Public License (GPL), version 2
7  */
8 
9 #include <linux/bitfield.h>
10 #include <linux/clk.h>
11 #include <linux/io.h>
12 #include <linux/iopoll.h>
13 #include <linux/module.h>
14 #include <linux/of_device.h>
15 #include <linux/platform_device.h>
16 #include <linux/regulator/driver.h>
17 #include <linux/regulator/of_regulator.h>
18 
19 /* STM32 VREFBUF registers */
20 #define STM32_VREFBUF_CSR		0x00
21 
22 /* STM32 VREFBUF CSR bitfields */
23 #define STM32_VRS			GENMASK(6, 4)
24 #define STM32_VRR			BIT(3)
25 #define STM32_HIZ			BIT(1)
26 #define STM32_ENVR			BIT(0)
27 
28 struct stm32_vrefbuf {
29 	void __iomem *base;
30 	struct clk *clk;
31 };
32 
33 static const unsigned int stm32_vrefbuf_voltages[] = {
34 	/* Matches resp. VRS = 000b, 001b, 010b, 011b */
35 	2500000, 2048000, 1800000, 1500000,
36 };
37 
38 static int stm32_vrefbuf_enable(struct regulator_dev *rdev)
39 {
40 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
41 	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
42 	int ret;
43 
44 	val = (val & ~STM32_HIZ) | STM32_ENVR;
45 	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
46 
47 	/*
48 	 * Vrefbuf startup time depends on external capacitor: wait here for
49 	 * VRR to be set. That means output has reached expected value.
50 	 * ~650us sleep should be enough for caps up to 1.5uF. Use 10ms as
51 	 * arbitrary timeout.
52 	 */
53 	ret = readl_poll_timeout(priv->base + STM32_VREFBUF_CSR, val,
54 				 !(val & STM32_VRR), 650, 10000);
55 	if (ret) {
56 		dev_err(&rdev->dev, "stm32 vrefbuf timed out!\n");
57 		val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
58 		val = (val & ~STM32_ENVR) | STM32_HIZ;
59 		writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
60 	}
61 
62 	return ret;
63 }
64 
65 static int stm32_vrefbuf_disable(struct regulator_dev *rdev)
66 {
67 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
68 	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
69 
70 	val = (val & ~STM32_ENVR) | STM32_HIZ;
71 	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
72 
73 	return 0;
74 }
75 
76 static int stm32_vrefbuf_is_enabled(struct regulator_dev *rdev)
77 {
78 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
79 
80 	return readl_relaxed(priv->base + STM32_VREFBUF_CSR) & STM32_ENVR;
81 }
82 
83 static int stm32_vrefbuf_set_voltage_sel(struct regulator_dev *rdev,
84 					 unsigned sel)
85 {
86 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
87 	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
88 
89 	val = (val & ~STM32_VRS) | FIELD_PREP(STM32_VRS, sel);
90 	writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
91 
92 	return 0;
93 }
94 
95 static int stm32_vrefbuf_get_voltage_sel(struct regulator_dev *rdev)
96 {
97 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
98 	u32 val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
99 
100 	return FIELD_GET(STM32_VRS, val);
101 }
102 
103 static const struct regulator_ops stm32_vrefbuf_volt_ops = {
104 	.enable		= stm32_vrefbuf_enable,
105 	.disable	= stm32_vrefbuf_disable,
106 	.is_enabled	= stm32_vrefbuf_is_enabled,
107 	.get_voltage_sel = stm32_vrefbuf_get_voltage_sel,
108 	.set_voltage_sel = stm32_vrefbuf_set_voltage_sel,
109 	.list_voltage	= regulator_list_voltage_table,
110 };
111 
112 static const struct regulator_desc stm32_vrefbuf_regu = {
113 	.name = "vref",
114 	.supply_name = "vdda",
115 	.volt_table = stm32_vrefbuf_voltages,
116 	.n_voltages = ARRAY_SIZE(stm32_vrefbuf_voltages),
117 	.ops = &stm32_vrefbuf_volt_ops,
118 	.type = REGULATOR_VOLTAGE,
119 	.owner = THIS_MODULE,
120 };
121 
122 static int stm32_vrefbuf_probe(struct platform_device *pdev)
123 {
124 	struct resource *res;
125 	struct stm32_vrefbuf *priv;
126 	struct regulator_config config = { };
127 	struct regulator_dev *rdev;
128 	int ret;
129 
130 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
131 	if (!priv)
132 		return -ENOMEM;
133 
134 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
135 	priv->base = devm_ioremap_resource(&pdev->dev, res);
136 	if (IS_ERR(priv->base))
137 		return PTR_ERR(priv->base);
138 
139 	priv->clk = devm_clk_get(&pdev->dev, NULL);
140 	if (IS_ERR(priv->clk))
141 		return PTR_ERR(priv->clk);
142 
143 	ret = clk_prepare_enable(priv->clk);
144 	if (ret) {
145 		dev_err(&pdev->dev, "clk prepare failed with error %d\n", ret);
146 		return ret;
147 	}
148 
149 	config.dev = &pdev->dev;
150 	config.driver_data = priv;
151 	config.of_node = pdev->dev.of_node;
152 	config.init_data = of_get_regulator_init_data(&pdev->dev,
153 						      pdev->dev.of_node,
154 						      &stm32_vrefbuf_regu);
155 
156 	rdev = regulator_register(&stm32_vrefbuf_regu, &config);
157 	if (IS_ERR(rdev)) {
158 		ret = PTR_ERR(rdev);
159 		dev_err(&pdev->dev, "register failed with error %d\n", ret);
160 		goto err_clk_dis;
161 	}
162 	platform_set_drvdata(pdev, rdev);
163 
164 	return 0;
165 
166 err_clk_dis:
167 	clk_disable_unprepare(priv->clk);
168 
169 	return ret;
170 }
171 
172 static int stm32_vrefbuf_remove(struct platform_device *pdev)
173 {
174 	struct regulator_dev *rdev = platform_get_drvdata(pdev);
175 	struct stm32_vrefbuf *priv = rdev_get_drvdata(rdev);
176 
177 	regulator_unregister(rdev);
178 	clk_disable_unprepare(priv->clk);
179 
180 	return 0;
181 };
182 
183 static const struct of_device_id stm32_vrefbuf_of_match[] = {
184 	{ .compatible = "st,stm32-vrefbuf", },
185 	{},
186 };
187 MODULE_DEVICE_TABLE(of, stm32_vrefbuf_of_match);
188 
189 static struct platform_driver stm32_vrefbuf_driver = {
190 	.probe = stm32_vrefbuf_probe,
191 	.remove = stm32_vrefbuf_remove,
192 	.driver = {
193 		.name  = "stm32-vrefbuf",
194 		.of_match_table = of_match_ptr(stm32_vrefbuf_of_match),
195 	},
196 };
197 module_platform_driver(stm32_vrefbuf_driver);
198 
199 MODULE_LICENSE("GPL v2");
200 MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
201 MODULE_DESCRIPTION("STMicroelectronics STM32 VREFBUF driver");
202 MODULE_ALIAS("platform:stm32-vrefbuf");
203