nvmem: brcm_nvram: new driver exposing Broadcom's NVRAM

This driver provides access to Broadcom's NVRAM.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210330111241.19401-6-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -278,4 +278,13 @@ config NVMEM_RMEM
 
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem-rmem.
+
+config NVMEM_BRCM_NVRAM
+	tristate "Broadcom's NVRAM support"
+	depends on ARCH_BCM_5301X || COMPILE_TEST
+	depends on HAS_IOMEM
+	help
+	  This driver provides support for Broadcom's NVRAM that can be accessed
+	  using I/O mapping.
+
 endif

drivers/nvmem/Makefile

@@ -57,3 +57,5 @@ obj-$(CONFIG_SPRD_EFUSE)	+= nvmem_sprd_efuse.o
 nvmem_sprd_efuse-y		:= sprd-efuse.o
 obj-$(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

drivers/nvmem/brcm_nvram.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+
+struct brcm_nvram {
+	struct device *dev;
+	void __iomem *base;
+};
+
+static int brcm_nvram_read(void *context, unsigned int offset, void *val,
+			   size_t bytes)
+{
+	struct brcm_nvram *priv = context;
+	u8 *dst = val;
+
+	while (bytes--)
+		*dst++ = readb(priv->base + offset++);
+
+	return 0;
+}
+
+static int brcm_nvram_probe(struct platform_device *pdev)
+{
+	struct nvmem_config config = {
+		.name = "brcm-nvram",
+		.reg_read = brcm_nvram_read,
+	};
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	struct brcm_nvram *priv;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	priv->dev = dev;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	config.dev = dev;
+	config.priv = priv;
+	config.size = resource_size(res);
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
+}
+
+static const struct of_device_id brcm_nvram_of_match_table[] = {
+	{ .compatible = "brcm,nvram", },
+	{},
+};
+
+static struct platform_driver brcm_nvram_driver = {
+	.probe = brcm_nvram_probe,
+	.driver = {
+		.name = "brcm_nvram",
+		.of_match_table = brcm_nvram_of_match_table,
+	},
+};
+
+static int __init brcm_nvram_init(void)
+{
+	return platform_driver_register(&brcm_nvram_driver);
+}
+
+subsys_initcall_sync(brcm_nvram_init);
+
+MODULE_AUTHOR("Rafał Miłecki");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(of, brcm_nvram_of_match_table);