1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Freescale MXS On-Chip OTP driver
4  *
5  * Copyright (C) 2015 Stefan Wahren <stefan.wahren@i2se.com>
6  *
7  * Based on the driver from Huang Shijie and Christoph G. Baumann
8  */
9 #include <linux/clk.h>
10 #include <linux/delay.h>
11 #include <linux/device.h>
12 #include <linux/err.h>
13 #include <linux/io.h>
14 #include <linux/module.h>
15 #include <linux/nvmem-provider.h>
16 #include <linux/of_device.h>
17 #include <linux/platform_device.h>
18 #include <linux/slab.h>
19 #include <linux/stmp_device.h>
20 
21 /* OCOTP registers and bits */
22 
23 #define BM_OCOTP_CTRL_RD_BANK_OPEN	BIT(12)
24 #define BM_OCOTP_CTRL_ERROR		BIT(9)
25 #define BM_OCOTP_CTRL_BUSY		BIT(8)
26 
27 #define OCOTP_TIMEOUT		10000
28 #define OCOTP_DATA_OFFSET	0x20
29 
30 struct mxs_ocotp {
31 	struct clk *clk;
32 	void __iomem *base;
33 	struct nvmem_device *nvmem;
34 };
35 
mxs_ocotp_wait(struct mxs_ocotp * otp)36 static int mxs_ocotp_wait(struct mxs_ocotp *otp)
37 {
38 	int timeout = OCOTP_TIMEOUT;
39 	unsigned int status = 0;
40 
41 	while (timeout--) {
42 		status = readl(otp->base);
43 
44 		if (!(status & (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)))
45 			break;
46 
47 		cpu_relax();
48 	}
49 
50 	if (status & BM_OCOTP_CTRL_BUSY)
51 		return -EBUSY;
52 	else if (status & BM_OCOTP_CTRL_ERROR)
53 		return -EIO;
54 
55 	return 0;
56 }
57 
mxs_ocotp_read(void * context,unsigned int offset,void * val,size_t bytes)58 static int mxs_ocotp_read(void *context, unsigned int offset,
59 			  void *val, size_t bytes)
60 {
61 	struct mxs_ocotp *otp = context;
62 	u32 *buf = val;
63 	int ret;
64 
65 	ret = clk_enable(otp->clk);
66 	if (ret)
67 		return ret;
68 
69 	writel(BM_OCOTP_CTRL_ERROR, otp->base + STMP_OFFSET_REG_CLR);
70 
71 	ret = mxs_ocotp_wait(otp);
72 	if (ret)
73 		goto disable_clk;
74 
75 	/* open OCOTP banks for read */
76 	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_SET);
77 
78 	/* approximately wait 33 hclk cycles */
79 	udelay(1);
80 
81 	ret = mxs_ocotp_wait(otp);
82 	if (ret)
83 		goto close_banks;
84 
85 	while (bytes) {
86 		if ((offset < OCOTP_DATA_OFFSET) || (offset % 16)) {
87 			/* fill up non-data register */
88 			*buf++ = 0;
89 		} else {
90 			*buf++ = readl(otp->base + offset);
91 		}
92 
93 		bytes -= 4;
94 		offset += 4;
95 	}
96 
97 close_banks:
98 	/* close banks for power saving */
99 	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_CLR);
100 
101 disable_clk:
102 	clk_disable(otp->clk);
103 
104 	return ret;
105 }
106 
107 static struct nvmem_config ocotp_config = {
108 	.name = "mxs-ocotp",
109 	.stride = 16,
110 	.word_size = 4,
111 	.reg_read = mxs_ocotp_read,
112 };
113 
114 struct mxs_data {
115 	int size;
116 };
117 
118 static const struct mxs_data imx23_data = {
119 	.size = 0x220,
120 };
121 
122 static const struct mxs_data imx28_data = {
123 	.size = 0x2a0,
124 };
125 
126 static const struct of_device_id mxs_ocotp_match[] = {
127 	{ .compatible = "fsl,imx23-ocotp", .data = &imx23_data },
128 	{ .compatible = "fsl,imx28-ocotp", .data = &imx28_data },
129 	{ /* sentinel */},
130 };
131 MODULE_DEVICE_TABLE(of, mxs_ocotp_match);
132 
mxs_ocotp_action(void * data)133 static void mxs_ocotp_action(void *data)
134 {
135 	clk_unprepare(data);
136 }
137 
mxs_ocotp_probe(struct platform_device * pdev)138 static int mxs_ocotp_probe(struct platform_device *pdev)
139 {
140 	struct device *dev = &pdev->dev;
141 	const struct mxs_data *data;
142 	struct mxs_ocotp *otp;
143 	const struct of_device_id *match;
144 	int ret;
145 
146 	match = of_match_device(dev->driver->of_match_table, dev);
147 	if (!match || !match->data)
148 		return -EINVAL;
149 
150 	otp = devm_kzalloc(dev, sizeof(*otp), GFP_KERNEL);
151 	if (!otp)
152 		return -ENOMEM;
153 
154 	otp->base = devm_platform_ioremap_resource(pdev, 0);
155 	if (IS_ERR(otp->base))
156 		return PTR_ERR(otp->base);
157 
158 	otp->clk = devm_clk_get(&pdev->dev, NULL);
159 	if (IS_ERR(otp->clk))
160 		return PTR_ERR(otp->clk);
161 
162 	ret = clk_prepare(otp->clk);
163 	if (ret < 0) {
164 		dev_err(dev, "failed to prepare clk: %d\n", ret);
165 		return ret;
166 	}
167 
168 	ret = devm_add_action_or_reset(&pdev->dev, mxs_ocotp_action, otp->clk);
169 	if (ret)
170 		return ret;
171 
172 	data = match->data;
173 
174 	ocotp_config.size = data->size;
175 	ocotp_config.priv = otp;
176 	ocotp_config.dev = dev;
177 	otp->nvmem = devm_nvmem_register(dev, &ocotp_config);
178 	if (IS_ERR(otp->nvmem))
179 		return PTR_ERR(otp->nvmem);
180 
181 	platform_set_drvdata(pdev, otp);
182 
183 	return 0;
184 }
185 
186 static struct platform_driver mxs_ocotp_driver = {
187 	.probe = mxs_ocotp_probe,
188 	.driver = {
189 		.name = "mxs-ocotp",
190 		.of_match_table = mxs_ocotp_match,
191 	},
192 };
193 
194 module_platform_driver(mxs_ocotp_driver);
195 MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net");
196 MODULE_DESCRIPTION("driver for OCOTP in i.MX23/i.MX28");
197 MODULE_LICENSE("GPL v2");
198