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
 30struct mxs_ocotp {
 31	struct clk *clk;
 32	void __iomem *base;
 33	struct nvmem_device *nvmem;
 34};
 35
 36static 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
 58static 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
 97close_banks:
 98	/* close banks for power saving */
 99	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_CLR);
100
101disable_clk:
102	clk_disable(otp->clk);
103
104	return ret;
105}
106
107static struct nvmem_config ocotp_config = {
108	.name = "mxs-ocotp",
109	.stride = 16,
110	.word_size = 4,
111	.reg_read = mxs_ocotp_read,
112};
113
114struct mxs_data {
115	int size;
116};
117
118static const struct mxs_data imx23_data = {
119	.size = 0x220,
120};
121
122static const struct mxs_data imx28_data = {
123	.size = 0x2a0,
124};
125
126static 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};
131MODULE_DEVICE_TABLE(of, mxs_ocotp_match);
132
133static void mxs_ocotp_action(void *data)
134{
135	clk_unprepare(data);
136}
137
138static 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
186static 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
194module_platform_driver(mxs_ocotp_driver);
195MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net");
196MODULE_DESCRIPTION("driver for OCOTP in i.MX23/i.MX28");
197MODULE_LICENSE("GPL v2");