[PATCH V4 RFC 2/3] nvmem: add driver for ocotp in i.MX23 and i.MX28

[Stefan Wahren]

This patch brings read-only support for the On-Chip OTP cells
in the i.MX23 and i.MX28 processor. The driver implements the
new NVMEM provider API.

Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
---
 drivers/nvmem/Kconfig     |   11 ++
 drivers/nvmem/Makefile    |    1 +
 drivers/nvmem/mxs-ocotp.c |  252 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 264 insertions(+)
 create mode 100644 drivers/nvmem/mxs-ocotp.c

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 8db2978..f7ff940 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -36,4 +36,15 @@ config NVMEM_SUNXI_SID
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem_sunxi_sid.
 
+config MXS_OCOTP
+	tristate "Freescale MXS On-Chip OTP Memory Support"
+	depends on ARCH_MXS
+	help
+	  If you say Y here, you will get readonly access to the
+	  One Time Programmable memory pages that are stored
+	  on the Freescale i.MX23/i.MX28 processor.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called mxs-ocotp.
+
 endif
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 4328b93..b450f8d 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_QCOM_QFPROM)	+= nvmem_qfprom.o
 nvmem_qfprom-y			:= qfprom.o
 obj-$(CONFIG_NVMEM_SUNXI_SID)	+= nvmem_sunxi_sid.o
 nvmem_sunxi_sid-y		:= sunxi_sid.o
+obj-$(CONFIG_MXS_OCOTP)		+= mxs-ocotp.o
diff --git a/drivers/nvmem/mxs-ocotp.c b/drivers/nvmem/mxs-ocotp.c
new file mode 100644
index 0000000..9ee146b
--- /dev/null
+++ b/drivers/nvmem/mxs-ocotp.c
@@ -0,0 +1,252 @@
+/*
+ * Freescale MXS On-Chip OTP driver
+ *
+ * Copyright (C) 2015 Stefan Wahren <stefan.wahren at i2se.com>
+ *
+ * Based on the driver from Huang Shijie and Christoph G. Baumann
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/stmp_device.h>
+
+/* OCOTP registers and bits */
+
+#define BM_OCOTP_CTRL_RD_BANK_OPEN	BIT(12)
+#define BM_OCOTP_CTRL_ERROR		BIT(9)
+#define BM_OCOTP_CTRL_BUSY		BIT(8)
+
+#define OCOTP_TIMEOUT		10000
+#define OCOTP_DATA_OFFSET	0x20
+
+struct mxs_ocotp {
+	struct clk *clk;
+	void __iomem *base;
+	struct nvmem_device *nvmem;
+};
+
+static int mxs_ocotp_wait(struct mxs_ocotp *otp)
+{
+	int timeout = OCOTP_TIMEOUT;
+	unsigned int status = 0;
+
+	while (timeout--) {
+		status = readl(otp->base);
+
+		if (!(status & (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)))
+			break;
+
+		cpu_relax();
+	}
+
+	if (status & BM_OCOTP_CTRL_BUSY)
+		return -EBUSY;
+	else if (status & BM_OCOTP_CTRL_ERROR)
+		return -EIO;
+
+	return 0;
+}
+
+static int mxs_ocotp_read(void *context, const void *reg, size_t reg_size,
+			  void *val, size_t val_size)
+{
+	struct mxs_ocotp *otp = context;
+	unsigned int offset = *(u32 *)reg;
+	u32 *buf = val;
+	int ret = 0;
+
+	writel(BM_OCOTP_CTRL_ERROR, otp->base + STMP_OFFSET_REG_CLR);
+
+	ret = mxs_ocotp_wait(otp);
+	if (ret)
+		return ret;
+
+	/* open OCOTP banks for read */
+	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_SET);
+
+	/* approximately wait 33 hclk cycles */
+	udelay(1);
+
+	ret = mxs_ocotp_wait(otp);
+	if (ret)
+		goto close_banks;
+
+	while (val_size) {
+		if ((offset < OCOTP_DATA_OFFSET) || (offset % 16)) {
+			/* fill up non-data register */
+			*buf = 0;
+		} else {
+			*buf = readl(otp->base + offset);
+		}
+
+		buf++;
+		val_size--;
+		offset += reg_size;
+	}
+
+close_banks:
+	/* close banks for power saving */
+	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_CLR);
+
+	return ret;
+}
+
+static int mxs_ocotp_write(void *context, const void *data, size_t count)
+{
+	/* We don't want to support writing */
+	return 0;
+}
+
+static bool mxs_ocotp_writeable_reg(struct device *dev, unsigned int reg)
+{
+	return false;
+}
+
+static struct nvmem_config ocotp_config = {
+	.name = "mxs-ocotp",
+	.owner = THIS_MODULE,
+};
+
+static const struct regmap_range imx23_ranges[] = {
+	regmap_reg_range(OCOTP_DATA_OFFSET, 0x210),
+};
+
+static const struct regmap_access_table imx23_access = {
+	.yes_ranges = imx23_ranges,
+	.n_yes_ranges = ARRAY_SIZE(imx23_ranges),
+};
+
+static const struct regmap_range imx28_ranges[] = {
+	regmap_reg_range(OCOTP_DATA_OFFSET, 0x290),
+};
+
+static const struct regmap_access_table imx28_access = {
+	.yes_ranges = imx28_ranges,
+	.n_yes_ranges = ARRAY_SIZE(imx28_ranges),
+};
+
+static struct regmap_bus mxs_ocotp_bus = {
+	.read = mxs_ocotp_read,
+	.write = mxs_ocotp_write, /* make regmap_init() happy */
+	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
+	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
+};
+
+static struct regmap_config mxs_ocotp_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 16,
+	.writeable_reg = mxs_ocotp_writeable_reg,
+};
+
+static const struct of_device_id mxs_ocotp_match[] = {
+	{ .compatible = "fsl,imx23-ocotp", .data = &imx23_access },
+	{ .compatible = "fsl,imx28-ocotp", .data = &imx28_access },
+	{ /* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, mxs_ocotp_match);
+
+static int mxs_ocotp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mxs_ocotp *otp;
+	struct resource *res;
+	const struct of_device_id *match;
+	struct regmap *regmap;
+	const struct regmap_access_table *access;
+	int ret;
+
+	match = of_match_device(dev->driver->of_match_table, dev);
+	if (!match || !match->data)
+		return -EINVAL;
+
+	otp = devm_kzalloc(dev, sizeof(*otp), GFP_KERNEL);
+	if (!otp)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	otp->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(otp->base))
+		return PTR_ERR(otp->base);
+
+	otp->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(otp->clk))
+		return PTR_ERR(otp->clk);
+
+	ret = clk_prepare(otp->clk);
+	if (ret < 0) {
+		dev_err(dev, "failed to prepare clk: %d\n", ret);
+		return ret;
+	}
+
+	access = match->data;
+	mxs_ocotp_config.rd_table = access;
+	mxs_ocotp_config.max_register = access->yes_ranges[0].range_max;
+
+	regmap = devm_regmap_init(dev, &mxs_ocotp_bus, otp, &mxs_ocotp_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "regmap init failed\n");
+		ret = PTR_ERR(regmap);
+		goto err_clk;
+	}
+
+	ocotp_config.dev = dev;
+	otp->nvmem = nvmem_register(&ocotp_config);
+	if (IS_ERR(otp->nvmem)) {
+		ret = PTR_ERR(otp->nvmem);
+		goto err_clk;
+	}
+
+	platform_set_drvdata(pdev, otp);
+
+	return 0;
+
+err_clk:
+	clk_unprepare(otp->clk);
+
+	return ret;
+}
+
+static int mxs_ocotp_remove(struct platform_device *pdev)
+{
+	struct mxs_ocotp *otp = platform_get_drvdata(pdev);
+
+	clk_unprepare(otp->clk);
+
+	return nvmem_unregister(otp->nvmem);
+}
+
+static struct platform_driver mxs_ocotp_driver = {
+	.probe = mxs_ocotp_probe,
+	.remove = mxs_ocotp_remove,
+	.driver = {
+		.name = "mxs-ocotp",
+		.of_match_table = mxs_ocotp_match,
+	},
+};
+
+module_platform_driver(mxs_ocotp_driver);
+MODULE_AUTHOR("Stefan Wahren <stefan.wahren at i2se.com>");
+MODULE_DESCRIPTION("driver for OCOTP in i.MX23/i.MX28");
+MODULE_LICENSE("GPL");
-- 
1.7.9.5