nvmem: add driver for ocotp in i.MX23 and i.MX28

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@i2se.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 270 insertions, 0 deletions

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 208a1cb6e4bf..a6d80536fd58 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -25,6 +25,17 @@ config NVMEM_IMX_OCOTP
           This driver can also be built as a module. If so, the module
           will be called nvmem-imx-ocotp.
 
+config NVMEM_MXS_OCOTP
+        tristate "Freescale MXS On-Chip OTP Memory Support"
+        depends on ARCH_MXS || COMPILE_TEST
+        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 nvmem-mxs-ocotp.
+
 config QCOM_QFPROM
         tristate "QCOM QFPROM Support"
         depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 2ddf0e88af3c..9322116d21ec 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -8,6 +8,8 @@ nvmem_core-y			:= core.o
 # Devices
 obj-$(CONFIG_NVMEM_IMX_OCOTP)   += nvmem-imx-ocotp.o
 nvmem-imx-ocotp-y               := imx-ocotp.o
+obj-$(CONFIG_NVMEM_MXS_OCOTP)   += nvmem-mxs-ocotp.o
+nvmem-mxs-ocotp-y               := mxs-ocotp.o
 obj-$(CONFIG_QCOM_QFPROM)       += nvmem_qfprom.o
 nvmem_qfprom-y                  := qfprom.o
 obj-$(CONFIG_NVMEM_SUNXI_SID)   += nvmem_sunxi_sid.o
diff --git a/drivers/nvmem/mxs-ocotp.c b/drivers/nvmem/mxs-ocotp.c
new file mode 100644
index 000000000000..8ba19bba3156
--- /dev/null
+++ b/drivers/nvmem/mxs-ocotp.c
@@ -0,0 +1,257 @@
+/*
+ * Freescale MXS On-Chip OTP driver
+ *
+ * Copyright (C) 2015 Stefan Wahren <stefan.wahren@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/nvmem-provider.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;
+
+        ret = clk_enable(otp->clk);
+        if (ret)
+                return ret;
+
+        writel(BM_OCOTP_CTRL_ERROR, otp->base + STMP_OFFSET_REG_CLR);
+
+        ret = mxs_ocotp_wait(otp);
+        if (ret)
+                goto disable_clk;
+
+        /* 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);
+
+disable_clk:
+        clk_disable(otp->clk);
+
+        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@i2se.com>");
+MODULE_DESCRIPTION("driver for OCOTP in i.MX23/i.MX28");
+MODULE_LICENSE("GPL v2");