xref: /openbmc/linux/drivers/iio/adc/lpc18xx_adc.c (revision 4004912e)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * IIO ADC driver for NXP LPC18xx ADC
4  *
5  * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
6  *
7  * UNSUPPORTED hardware features:
8  *  - Hardware triggers
9  *  - Burst mode
10  *  - Interrupts
11  *  - DMA
12  */
13 
14 #include <linux/clk.h>
15 #include <linux/err.h>
16 #include <linux/iio/iio.h>
17 #include <linux/iio/driver.h>
18 #include <linux/io.h>
19 #include <linux/iopoll.h>
20 #include <linux/mod_devicetable.h>
21 #include <linux/module.h>
22 #include <linux/mutex.h>
23 #include <linux/platform_device.h>
24 #include <linux/regulator/consumer.h>
25 
26 /* LPC18XX ADC registers and bits */
27 #define LPC18XX_ADC_CR			0x000
28 #define  LPC18XX_ADC_CR_CLKDIV_SHIFT	8
29 #define  LPC18XX_ADC_CR_PDN		BIT(21)
30 #define  LPC18XX_ADC_CR_START_NOW	(0x1 << 24)
31 #define LPC18XX_ADC_GDR			0x004
32 
33 /* Data register bits */
34 #define LPC18XX_ADC_SAMPLE_SHIFT	6
35 #define LPC18XX_ADC_SAMPLE_MASK		0x3ff
36 #define LPC18XX_ADC_CONV_DONE		BIT(31)
37 
38 /* Clock should be 4.5 MHz or less */
39 #define LPC18XX_ADC_CLK_TARGET		4500000
40 
41 struct lpc18xx_adc {
42 	struct regulator *vref;
43 	void __iomem *base;
44 	struct device *dev;
45 	struct mutex lock;
46 	struct clk *clk;
47 	u32 cr_reg;
48 };
49 
50 #define LPC18XX_ADC_CHAN(_idx) {				\
51 	.type = IIO_VOLTAGE,					\
52 	.indexed = 1,						\
53 	.channel = _idx,					\
54 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
55 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
56 }
57 
58 static const struct iio_chan_spec lpc18xx_adc_iio_channels[] = {
59 	LPC18XX_ADC_CHAN(0),
60 	LPC18XX_ADC_CHAN(1),
61 	LPC18XX_ADC_CHAN(2),
62 	LPC18XX_ADC_CHAN(3),
63 	LPC18XX_ADC_CHAN(4),
64 	LPC18XX_ADC_CHAN(5),
65 	LPC18XX_ADC_CHAN(6),
66 	LPC18XX_ADC_CHAN(7),
67 };
68 
lpc18xx_adc_read_chan(struct lpc18xx_adc * adc,unsigned int ch)69 static int lpc18xx_adc_read_chan(struct lpc18xx_adc *adc, unsigned int ch)
70 {
71 	int ret;
72 	u32 reg;
73 
74 	reg = adc->cr_reg | BIT(ch) | LPC18XX_ADC_CR_START_NOW;
75 	writel(reg, adc->base + LPC18XX_ADC_CR);
76 
77 	ret = readl_poll_timeout(adc->base + LPC18XX_ADC_GDR, reg,
78 				 reg & LPC18XX_ADC_CONV_DONE, 3, 9);
79 	if (ret) {
80 		dev_warn(adc->dev, "adc read timed out\n");
81 		return ret;
82 	}
83 
84 	return (reg >> LPC18XX_ADC_SAMPLE_SHIFT) & LPC18XX_ADC_SAMPLE_MASK;
85 }
86 
lpc18xx_adc_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)87 static int lpc18xx_adc_read_raw(struct iio_dev *indio_dev,
88 				struct iio_chan_spec const *chan,
89 				int *val, int *val2, long mask)
90 {
91 	struct lpc18xx_adc *adc = iio_priv(indio_dev);
92 
93 	switch (mask) {
94 	case IIO_CHAN_INFO_RAW:
95 		mutex_lock(&adc->lock);
96 		*val = lpc18xx_adc_read_chan(adc, chan->channel);
97 		mutex_unlock(&adc->lock);
98 		if (*val < 0)
99 			return *val;
100 
101 		return IIO_VAL_INT;
102 
103 	case IIO_CHAN_INFO_SCALE:
104 		*val = regulator_get_voltage(adc->vref) / 1000;
105 		*val2 = 10;
106 
107 		return IIO_VAL_FRACTIONAL_LOG2;
108 	}
109 
110 	return -EINVAL;
111 }
112 
113 static const struct iio_info lpc18xx_adc_info = {
114 	.read_raw = lpc18xx_adc_read_raw,
115 };
116 
lpc18xx_clear_cr_reg(void * data)117 static void lpc18xx_clear_cr_reg(void *data)
118 {
119 	struct lpc18xx_adc *adc = data;
120 
121 	writel(0, adc->base + LPC18XX_ADC_CR);
122 }
123 
lpc18xx_regulator_disable(void * vref)124 static void lpc18xx_regulator_disable(void *vref)
125 {
126 	regulator_disable(vref);
127 }
128 
lpc18xx_adc_probe(struct platform_device * pdev)129 static int lpc18xx_adc_probe(struct platform_device *pdev)
130 {
131 	struct iio_dev *indio_dev;
132 	struct lpc18xx_adc *adc;
133 	unsigned int clkdiv;
134 	unsigned long rate;
135 	int ret;
136 
137 	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
138 	if (!indio_dev)
139 		return -ENOMEM;
140 
141 	adc = iio_priv(indio_dev);
142 	adc->dev = &pdev->dev;
143 	mutex_init(&adc->lock);
144 
145 	adc->base = devm_platform_ioremap_resource(pdev, 0);
146 	if (IS_ERR(adc->base))
147 		return PTR_ERR(adc->base);
148 
149 	adc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
150 	if (IS_ERR(adc->clk))
151 		return dev_err_probe(&pdev->dev, PTR_ERR(adc->clk),
152 				     "error getting clock\n");
153 
154 	adc->vref = devm_regulator_get(&pdev->dev, "vref");
155 	if (IS_ERR(adc->vref))
156 		return dev_err_probe(&pdev->dev, PTR_ERR(adc->vref),
157 				     "error getting regulator\n");
158 
159 	indio_dev->name = dev_name(&pdev->dev);
160 	indio_dev->info = &lpc18xx_adc_info;
161 	indio_dev->modes = INDIO_DIRECT_MODE;
162 	indio_dev->channels = lpc18xx_adc_iio_channels;
163 	indio_dev->num_channels = ARRAY_SIZE(lpc18xx_adc_iio_channels);
164 
165 	ret = regulator_enable(adc->vref);
166 	if (ret) {
167 		dev_err(&pdev->dev, "unable to enable regulator\n");
168 		return ret;
169 	}
170 
171 	ret = devm_add_action_or_reset(&pdev->dev, lpc18xx_regulator_disable, adc->vref);
172 	if (ret)
173 		return ret;
174 
175 	rate = clk_get_rate(adc->clk);
176 	clkdiv = DIV_ROUND_UP(rate, LPC18XX_ADC_CLK_TARGET);
177 
178 	adc->cr_reg = (clkdiv << LPC18XX_ADC_CR_CLKDIV_SHIFT) |
179 			LPC18XX_ADC_CR_PDN;
180 	writel(adc->cr_reg, adc->base + LPC18XX_ADC_CR);
181 
182 	ret = devm_add_action_or_reset(&pdev->dev, lpc18xx_clear_cr_reg, adc);
183 	if (ret)
184 		return ret;
185 
186 	return devm_iio_device_register(&pdev->dev, indio_dev);
187 }
188 
189 static const struct of_device_id lpc18xx_adc_match[] = {
190 	{ .compatible = "nxp,lpc1850-adc" },
191 	{ /* sentinel */ }
192 };
193 MODULE_DEVICE_TABLE(of, lpc18xx_adc_match);
194 
195 static struct platform_driver lpc18xx_adc_driver = {
196 	.probe	= lpc18xx_adc_probe,
197 	.driver	= {
198 		.name = "lpc18xx-adc",
199 		.of_match_table = lpc18xx_adc_match,
200 	},
201 };
202 module_platform_driver(lpc18xx_adc_driver);
203 
204 MODULE_DESCRIPTION("LPC18xx ADC driver");
205 MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
206 MODULE_LICENSE("GPL v2");
207