nvmem: airoha: Add support for SMC eFUSE

Add support for SMC eFUSE on AN7581 SoC. The SoC have 2 set of 2048 bits of eFUSE that are used to read calibration value for PCIe, Thermal, USB and other specific info of the SoC like revision and HW device present.

eFuse value are taken by sending SMC command. ATF is responsible of validaing the data and rejecting reading protected data (like Private Key). In such case the SMC command will return non-zero value on a0 register.

Signed-off-by Christian Marangi <[email protected]>

---
 drivers/nvmem/Kconfig             |  13 ++++
 drivers/nvmem/Makefile            |   2 +
 drivers/nvmem/airoha-smc-efuses.c | 118 ++++++++++++++++++++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 drivers/nvmem/airoha-smc-efuses.c

drivers/nvmem/Kconfig +13 -0

index 74ddbd0f79b0..95a399258538 100644
@@ -28,6 +28,19 @@ source "drivers/nvmem/layouts/Kconfig"
 
 # Devices
 
+config NVMEM_AIROHA_SMC_EFUSES
+	tristate "Airoha SMC eFuse support"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	depends on HAVE_ARM_SMCCC
+	default ARCH_AIROHA
+	help
+	  Say y here to enable support for reading eFuses on Airoha AN7581
+	  SoCs. These are e.g. used to store factory programmed
+	  calibration data required for the PCIe or the USB-C PHY or Thermal.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called nvmem-airoha-smc-efuses.
+
 config NVMEM_AN8855_EFUSE
 	tristate "Airoha AN8855 eFuse support"
 	depends on COMPILE_TEST

drivers/nvmem/Makefile +2 -0

index 7252b8ec88d4..f6f2bc51dee1 100644
@@ -10,6 +10,8 @@ nvmem_layouts-y			:= layouts.o
 obj-y				+= layouts/
 
 # Devices
+obj-$(CONFIG_NVMEM_AIROHA_SMC_EFUSES)	+= nvmem-airoha-smc-efuses.o
+nvmem-airoha-smc-efuses-y 		:= airoha-smc-efuses.o
 obj-$(CONFIG_NVMEM_AN8855_EFUSE)	+= nvmem-an8855-efuse.o
 nvmem-an8855-efuse-y 			:= an8855-efuse.o
 obj-$(CONFIG_NVMEM_APPLE_EFUSES)	+= nvmem-apple-efuses.o

drivers/nvmem/airoha-smc-efuses.c new file +73 -0

new file mode 100644
index 000000000000..bb279d149519
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Author: Christian Marangi <[email protected]>
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#define AIROHA_SMC_EFUSE_FID		0x82000001
+#define AIROHA_SMC_EFUSE_SUB_ID_READ	0x44414552
+
+#define AIROHA_EFUSE_CELLS		64
+
+struct airoha_efuse_bank_priv {
+	u8 bank_index;
+};
+
+static int airoha_efuse_read(void *context, unsigned int offset,
+			     void *val, size_t bytes)
+{
+	struct regmap *regmap = context;
+
+	return regmap_bulk_read(regmap, offset,
+				val, bytes / sizeof(u32));
+}
+
+static int airoha_efuse_reg_read(void *context, unsigned int offset,
+				 unsigned int *val)
+{
+	struct airoha_efuse_bank_priv *priv = context;
+	struct arm_smccc_res res;
+
+	arm_smccc_1_1_invoke(AIROHA_SMC_EFUSE_FID,
+			     AIROHA_SMC_EFUSE_SUB_ID_READ,
+			     priv->bank_index, offset, 0, 0, 0, 0, &res);
+
+	/* check if SMC reported an error */
+	if (res.a0)
+		return -EIO;
+
+	*val = res.a1;
+	return 0;
+}
+
+static const struct regmap_config airoha_efuse_regmap_config = {
+	.reg_read = airoha_efuse_reg_read,
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+};
+
+static int airoha_efuse_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	for_each_child_of_node_scoped(dev->of_node, child) {
+		struct nvmem_config airoha_nvmem_config = {
+			.name = "airoha-efuse",
+			.size = AIROHA_EFUSE_CELLS * sizeof(u32),
+			.stride = sizeof(u32),
+			.word_size = sizeof(u32),
+			.reg_read = airoha_efuse_read,
+		};
+		struct airoha_efuse_bank_priv *priv;
+		struct nvmem_device *nvmem;
+		struct regmap *regmap;
+		u32 bank;