[PATCH V2 2/2] nvmem: brcm_nvram: new driver exposing Broadcom's NVRAM

["Rafał Miłecki" <zajec5@gmail.com>]

From: Rafał Miłecki <rafal@milecki.pl>

This driver provides access to Broadcom's NVRAM.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
V2: Applied Srinivas's suggestions:
    * Simplified brcm_nvram_read
    * Drop unneeded check & prints from probe
    * Fixed MODULE_LICENSE
    * Switched to Broadcom specific binding & driver. This is such a trivial
      driver that even if we get another similar one, it probably won't be worth
      it to share their code.
    Thank you Srinivas!
---
 drivers/nvmem/Kconfig      |  9 +++++
 drivers/nvmem/Makefile     |  2 +
 drivers/nvmem/brcm_nvram.c | 78 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+)
 create mode 100644 drivers/nvmem/brcm_nvram.c

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 75d2594c16e1..d2a848fab82a 100644
--- a/drivers/nvmem/Kconfig
+++ b/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
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 5376b8e0dae5..bbea1410240a 100644
--- a/drivers/nvmem/Makefile
+++ b/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
diff --git a/drivers/nvmem/brcm_nvram.c b/drivers/nvmem/brcm_nvram.c
new file mode 100644
index 000000000000..bd2ecaaf4585
--- /dev/null
+++ b/drivers/nvmem/brcm_nvram.c
@@ -0,0 +1,78 @@
+// 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);
-- 
2.26.2