nvmem: an8855: Add support for Airoha AN8855 Switch EFUSE

Add support for Airoha AN8855 Switch EFUSE. These EFUSE might be used
for calibration data for the internal switch PHYs.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
Link: https://lore.kernel.org/r/20250912131415.303407-6-srini@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ansuel

drivers/nvmem/Kconfig

@@ -28,6 +28,17 @@ source "drivers/nvmem/layouts/Kconfig"
 
 # Devices
 
+config NVMEM_AN8855_EFUSE
+	tristate "Airoha AN8855 eFuse support"
+	depends on MFD_AIROHA_AN8855 || COMPILE_TEST
+	help
+	  Say y here to enable support for reading eFuses on Airoha AN8855
+	  Switch. These are e.g. used to store factory programmed
+	  calibration data required for the PHY.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called nvmem-an8855-efuse.
+
 config NVMEM_APPLE_EFUSES
 	tristate "Apple eFuse support"
 	depends on ARCH_APPLE || COMPILE_TEST

drivers/nvmem/Makefile

@@ -10,6 +10,8 @@ nvmem_layouts-y			:= layouts.o
 obj-y				+= layouts/
 
 # Devices
+obj-$(CONFIG_NVMEM_AN8855_EFUSE)	+= nvmem-an8855-efuse.o
+nvmem-an8855-efuse-y 			:= an8855-efuse.o
 obj-$(CONFIG_NVMEM_APPLE_EFUSES)	+= nvmem-apple-efuses.o
 nvmem-apple-efuses-y 			:= apple-efuses.o
 obj-$(CONFIG_NVMEM_APPLE_SPMI)		+= apple_nvmem_spmi.o

drivers/nvmem/an8855-efuse.c

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Airoha AN8855 Switch EFUSE Driver
+ */
+
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define AN8855_EFUSE_CELL		50
+
+#define AN8855_EFUSE_DATA0		0x1000a500
+#define   AN8855_EFUSE_R50O		GENMASK(30, 24)
+
+static int an8855_efuse_read(void *context, unsigned int offset,
+			     void *val, size_t bytes)
+{
+	struct regmap *regmap = context;
+
+	return regmap_bulk_read(regmap, AN8855_EFUSE_DATA0 + offset,
+				val, bytes / sizeof(u32));
+}
+
+static int an8855_efuse_probe(struct platform_device *pdev)
+{
+	struct nvmem_config an8855_nvmem_config = {
+		.name = "an8855-efuse",
+		.size = AN8855_EFUSE_CELL * sizeof(u32),
+		.stride = sizeof(u32),
+		.word_size = sizeof(u32),
+		.reg_read = an8855_efuse_read,
+	};
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct regmap *regmap;
+
+	/* Assign NVMEM priv to MFD regmap */
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (!regmap)
+		return -ENOENT;
+
+	an8855_nvmem_config.priv = regmap;
+	an8855_nvmem_config.dev = dev;
+	nvmem = devm_nvmem_register(dev, &an8855_nvmem_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id an8855_efuse_of_match[] = {
+	{ .compatible = "airoha,an8855-efuse", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, an8855_efuse_of_match);
+
+static struct platform_driver an8855_efuse_driver = {
+	.probe = an8855_efuse_probe,
+	.driver = {
+		.name = "an8855-efuse",
+		.of_match_table = an8855_efuse_of_match,
+	},
+};
+module_platform_driver(an8855_efuse_driver);
+
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_DESCRIPTION("Driver for AN8855 Switch EFUSE");
+MODULE_LICENSE("GPL");