nvmem: add driver for Layerscape SFP (Security Fuse Processor)

Add support for the Security Fuse Processor found on Layerscape SoCs.
This driver implements basic read access.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220220151527.17216-10-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -300,4 +300,16 @@ config NVMEM_BRCM_NVRAM
 	  This driver provides support for Broadcom's NVRAM that can be accessed
 	  using I/O mapping.
 
+config NVMEM_LAYERSCAPE_SFP
+	tristate "Layerscape SFP (Security Fuse Processor) support"
+	depends on ARCH_LAYERSCAPE || COMPILE_TEST
+	depends on HAS_IOMEM
+	help
+	  This driver provides support to read the eFuses on Freescale
+	  Layerscape SoC's. For example, the vendor provides a per part
+	  unique ID there.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called layerscape-sfp.
+
 endif

drivers/nvmem/Makefile

@@ -61,3 +61,5 @@ obj-$(CONFIG_NVMEM_RMEM) 	+= nvmem-rmem.o
 nvmem-rmem-y			:= rmem.o
 obj-$(CONFIG_NVMEM_BRCM_NVRAM)	+= nvmem_brcm_nvram.o
 nvmem_brcm_nvram-y		:= brcm_nvram.o
+obj-$(CONFIG_NVMEM_LAYERSCAPE_SFP)	+= nvmem-layerscape-sfp.o
+nvmem-layerscape-sfp-y		:= layerscape-sfp.o

drivers/nvmem/layerscape-sfp.c

@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Layerscape SFP driver
+ *
+ * Copyright (c) 2022 Michael Walle <michael@walle.cc>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#define LAYERSCAPE_SFP_OTP_OFFSET	0x0200
+
+struct layerscape_sfp_priv {
+	void __iomem *base;
+};
+
+struct layerscape_sfp_data {
+	int size;
+};
+
+static int layerscape_sfp_read(void *context, unsigned int offset, void *val,
+			       size_t bytes)
+{
+	struct layerscape_sfp_priv *priv = context;
+
+	memcpy_fromio(val, priv->base + LAYERSCAPE_SFP_OTP_OFFSET + offset,
+		      bytes);
+
+	return 0;
+}
+
+static struct nvmem_config layerscape_sfp_nvmem_config = {
+	.name = "fsl-sfp",
+	.reg_read = layerscape_sfp_read,
+};
+
+static int layerscape_sfp_probe(struct platform_device *pdev)
+{
+	const struct layerscape_sfp_data *data;
+	struct layerscape_sfp_priv *priv;
+	struct nvmem_device *nvmem;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	data = device_get_match_data(&pdev->dev);
+
+	layerscape_sfp_nvmem_config.size = data->size;
+	layerscape_sfp_nvmem_config.dev = &pdev->dev;
+	layerscape_sfp_nvmem_config.priv = priv;
+
+	nvmem = devm_nvmem_register(&pdev->dev, &layerscape_sfp_nvmem_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct layerscape_sfp_data ls1028a_data = {
+	.size = 0x88,
+};
+
+static const struct of_device_id layerscape_sfp_dt_ids[] = {
+	{ .compatible = "fsl,ls1028a-sfp", .data = &ls1028a_data },
+	{},
+};
+MODULE_DEVICE_TABLE(of, layerscape_sfp_dt_ids);
+
+static struct platform_driver layerscape_sfp_driver = {
+	.probe	= layerscape_sfp_probe,
+	.driver = {
+		.name	= "layerscape_sfp",
+		.of_match_table = layerscape_sfp_dt_ids,
+	},
+};
+module_platform_driver(layerscape_sfp_driver);
+
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_DESCRIPTION("Layerscape Security Fuse Processor driver");
+MODULE_LICENSE("GPL");