nvmem: Add driver for the i.MX IIM

This adds a readonly nvmem driver for the i.MX IC Identification Module
(IIM). The IIM is found on the older i.MX SoCs like the i.MX25, i.MX27,
i.MX31, i.MX35, i.MX51 and the i.MX53.

The IIM can control up to 8 fuse banks with 256 bit each. Not all of the
banks are equipped on the different SoCs. The actual number of fuses
differ from 512 on the i.MX27 and 1152 on the i.MX53.

The fuses are one time writable, but writing is currently not supported
in the driver.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -13,6 +13,17 @@ menuconfig NVMEM
 
 if NVMEM
 
+config NVMEM_IMX_IIM
+	tristate "i.MX IC Identification Module support"
+	depends on ARCH_MXC || COMPILE_TEST
+	help
+	  This is a driver for the IC Identification Module (IIM) available on
+	  i.MX SoCs, providing access to 4 Kbits of programmable
+	  eFuses.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nvmem-imx-iim.
+
 config NVMEM_IMX_OCOTP
 	tristate "i.MX6 On-Chip OTP Controller support"
 	depends on SOC_IMX6 || COMPILE_TEST

drivers/nvmem/Makefile

@@ -8,6 +8,8 @@ nvmem_core-y			:= core.o
 # Devices
 obj-$(CONFIG_NVMEM_BCM_OCOTP)	+= nvmem-bcm-ocotp.o
 nvmem-bcm-ocotp-y		:= bcm-ocotp.o
+obj-$(CONFIG_NVMEM_IMX_IIM)	+= nvmem-imx-iim.o
+nvmem-imx-iim-y			:= imx-iim.o
 obj-$(CONFIG_NVMEM_IMX_OCOTP)	+= nvmem-imx-ocotp.o
 nvmem-imx-ocotp-y		:= imx-ocotp.o
 obj-$(CONFIG_NVMEM_LPC18XX_EEPROM)	+= nvmem_lpc18xx_eeprom.o

drivers/nvmem/imx-iim.c

@@ -0,0 +1,173 @@
+/*
+ * i.MX IIM driver
+ *
+ * Copyright (c) 2017 Pengutronix, Michael Grzeschik <m.grzeschik@pengutronix.de>
+ *
+ * Based on the barebox iim driver,
+ * Copyright (c) 2010 Baruch Siach <baruch@tkos.co.il>,
+ *	Orex Computed Radiography
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/clk.h>
+
+#define IIM_BANK_BASE(n)	(0x800 + 0x400 * (n))
+
+struct imx_iim_drvdata {
+	unsigned int nregs;
+};
+
+struct iim_priv {
+	void __iomem *base;
+	struct clk *clk;
+	struct nvmem_config nvmem;
+};
+
+static int imx_iim_read(void *context, unsigned int offset,
+			  void *buf, size_t bytes)
+{
+	struct iim_priv *iim = context;
+	int i, ret;
+	u8 *buf8 = buf;
+
+	ret = clk_prepare_enable(iim->clk);
+	if (ret)
+		return ret;
+
+	for (i = offset; i < offset + bytes; i++) {
+		int bank = i >> 5;
+		int reg = i & 0x1f;
+
+		*buf8++ = readl(iim->base + IIM_BANK_BASE(bank) + reg * 4);
+	}
+
+	clk_disable_unprepare(iim->clk);
+
+	return 0;
+}
+
+static struct imx_iim_drvdata imx27_drvdata = {
+	.nregs = 2 * 32,
+};
+
+static struct imx_iim_drvdata imx25_imx31_imx35_drvdata = {
+	.nregs = 3 * 32,
+};
+
+static struct imx_iim_drvdata imx51_drvdata = {
+	.nregs = 4 * 32,
+};
+
+static struct imx_iim_drvdata imx53_drvdata = {
+	.nregs = 4 * 32 + 16,
+};
+
+static const struct of_device_id imx_iim_dt_ids[] = {
+	{
+		.compatible = "fsl,imx25-iim",
+		.data = &imx25_imx31_imx35_drvdata,
+	}, {
+		.compatible = "fsl,imx27-iim",
+		.data = &imx27_drvdata,
+	}, {
+		.compatible = "fsl,imx31-iim",
+		.data = &imx25_imx31_imx35_drvdata,
+	}, {
+		.compatible = "fsl,imx35-iim",
+		.data = &imx25_imx31_imx35_drvdata,
+	}, {
+		.compatible = "fsl,imx51-iim",
+		.data = &imx51_drvdata,
+	}, {
+		.compatible = "fsl,imx53-iim",
+		.data = &imx53_drvdata,
+	}, {
+		/* sentinel */
+	},
+};
+MODULE_DEVICE_TABLE(of, imx_iim_dt_ids);
+
+static int imx_iim_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *of_id;
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	struct iim_priv *iim;
+	struct nvmem_device *nvmem;
+	struct nvmem_config *cfg;
+	const struct imx_iim_drvdata *drvdata = NULL;
+
+	iim = devm_kzalloc(dev, sizeof(*iim), GFP_KERNEL);
+	if (!iim)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	iim->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(iim->base))
+		return PTR_ERR(iim->base);
+
+	of_id = of_match_device(imx_iim_dt_ids, dev);
+	if (!of_id)
+		return -ENODEV;
+
+	drvdata = of_id->data;
+
+	iim->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(iim->clk))
+		return PTR_ERR(iim->clk);
+
+	cfg = &iim->nvmem;
+
+	cfg->name = "imx-iim",
+	cfg->read_only = true,
+	cfg->word_size = 1,
+	cfg->stride = 1,
+	cfg->owner = THIS_MODULE,
+	cfg->reg_read = imx_iim_read,
+	cfg->dev = dev;
+	cfg->size = drvdata->nregs;
+	cfg->priv = iim;
+
+	nvmem = nvmem_register(cfg);
+	if (IS_ERR(nvmem))
+		return PTR_ERR(nvmem);
+
+	platform_set_drvdata(pdev, nvmem);
+
+	return 0;
+}
+
+static int imx_iim_remove(struct platform_device *pdev)
+{
+	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
+
+	return nvmem_unregister(nvmem);
+}
+
+static struct platform_driver imx_iim_driver = {
+	.probe	= imx_iim_probe,
+	.remove	= imx_iim_remove,
+	.driver = {
+		.name	= "imx-iim",
+		.of_match_table = imx_iim_dt_ids,
+	},
+};
+module_platform_driver(imx_iim_driver);
+
+MODULE_AUTHOR("Michael Grzeschik <m.grzeschik@pengutronix.de>");
+MODULE_DESCRIPTION("i.MX IIM driver");
+MODULE_LICENSE("GPL v2");