nvmem: zynqmp_nvmem: Add support to access efuse

Add support to read/write efuse memory map of ZynqMP.
Below are the offsets of ZynqMP efuse memory map
	0 - SOC version(read only)
	0xC - 0xFC -ZynqMP specific purpose efuses
	0x100 - 0x17F - Physical Unclonable Function(PUF)
                efuses repurposed as user efuses
Signed-off-by: Praveen Teja Kundanala <praveen.teja.kundanala@amd.com>
Acked-by: Kalyani Akula <Kalyani.akula@amd.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240224114516.86365-8-srinivas.kandagatla@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/zynqmp_nvmem.c

@@ -4,6 +4,7 @@
  * Copyright (C) 2022 - 2023, Advanced Micro Devices, Inc.
  */
 
+#include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/nvmem-provider.h>
 #include <linux/of.h>
@@ -11,24 +12,189 @@
 #include <linux/firmware/xlnx-zynqmp.h>
 
 #define SILICON_REVISION_MASK 0xF
+#define P_USER_0_64_UPPER_MASK	GENMASK(31, 16)
+#define P_USER_127_LOWER_4_BIT_MASK GENMASK(3, 0)
+#define WORD_INBYTES		4
+#define SOC_VER_SIZE		0x4
+#define EFUSE_MEMORY_SIZE	0x177
+#define UNUSED_SPACE		0x8
+#define ZYNQMP_NVMEM_SIZE	(SOC_VER_SIZE + UNUSED_SPACE + \
+				 EFUSE_MEMORY_SIZE)
+#define SOC_VERSION_OFFSET	0x0
+#define EFUSE_START_OFFSET	0xC
+#define EFUSE_END_OFFSET	0xFC
+#define EFUSE_PUF_START_OFFSET	0x100
+#define EFUSE_PUF_MID_OFFSET	0x140
+#define EFUSE_PUF_END_OFFSET	0x17F
+#define EFUSE_NOT_ENABLED	29
 
+/*
+ * efuse access type
+ */
+enum efuse_access {
+	EFUSE_READ = 0,
+	EFUSE_WRITE
+};
+
+/**
+ * struct xilinx_efuse - the basic structure
+ * @src:	address of the buffer to store the data to be write/read
+ * @size:	read/write word count
+ * @offset:	read/write offset
+ * @flag:	0 - represents efuse read and 1- represents efuse write
+ * @pufuserfuse:0 - represents non-puf efuses, offset is used for read/write
+ *		1 - represents puf user fuse row number.
+ *
+ * this structure stores all the required details to
+ * read/write efuse memory.
+ */
+struct xilinx_efuse {
+	u64 src;
+	u32 size;
+	u32 offset;
+	enum efuse_access flag;
+	u32 pufuserfuse;
+};
+
+static int zynqmp_efuse_access(void *context, unsigned int offset,
+			       void *val, size_t bytes, enum efuse_access flag,
+			       unsigned int pufflag)
+{
+	struct device *dev = context;
+	struct xilinx_efuse *efuse;
+	dma_addr_t dma_addr;
+	dma_addr_t dma_buf;
+	size_t words = bytes / WORD_INBYTES;
+	int ret;
+	int value;
+	char *data;
+
+	if (bytes % WORD_INBYTES != 0) {
+		dev_err(dev, "Bytes requested should be word aligned\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (pufflag == 0 && offset % WORD_INBYTES) {
+		dev_err(dev, "Offset requested should be word aligned\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (pufflag == 1 && flag == EFUSE_WRITE) {
+		memcpy(&value, val, bytes);
+		if ((offset == EFUSE_PUF_START_OFFSET ||
+		     offset == EFUSE_PUF_MID_OFFSET) &&
+		    value & P_USER_0_64_UPPER_MASK) {
+			dev_err(dev, "Only lower 4 bytes are allowed to be programmed in P_USER_0 & P_USER_64\n");
+			return -EOPNOTSUPP;
+		}
+
+		if (offset == EFUSE_PUF_END_OFFSET &&
+		    (value & P_USER_127_LOWER_4_BIT_MASK)) {
+			dev_err(dev, "Only MSB 28 bits are allowed to be programmed for P_USER_127\n");
+			return -EOPNOTSUPP;
+		}
+	}
+
+	efuse = dma_alloc_coherent(dev, sizeof(struct xilinx_efuse),
+				   &dma_addr, GFP_KERNEL);
+	if (!efuse)
+		return -ENOMEM;
 
-static int zynqmp_nvmem_read(void *context, unsigned int offset,
-			     void *val, size_t bytes)
+	data = dma_alloc_coherent(dev, sizeof(bytes),
+				  &dma_buf, GFP_KERNEL);
+	if (!data) {
+		ret = -ENOMEM;
+		goto efuse_data_fail;
+	}
+
+	if (flag == EFUSE_WRITE) {
+		memcpy(data, val, bytes);
+		efuse->flag = EFUSE_WRITE;
+	} else {
+		efuse->flag = EFUSE_READ;
+	}
+
+	efuse->src = dma_buf;
+	efuse->size = words;
+	efuse->offset = offset;
+	efuse->pufuserfuse = pufflag;
+
+	zynqmp_pm_efuse_access(dma_addr, (u32 *)&ret);
+	if (ret != 0) {
+		if (ret == EFUSE_NOT_ENABLED) {
+			dev_err(dev, "efuse access is not enabled\n");
+			ret = -EOPNOTSUPP;
+		} else {
+			dev_err(dev, "Error in efuse read %x\n", ret);
+			ret = -EPERM;
+		}
+		goto efuse_access_err;
+	}
+
+	if (flag == EFUSE_READ)
+		memcpy(val, data, bytes);
+efuse_access_err:
+	dma_free_coherent(dev, sizeof(bytes),
+			  data, dma_buf);
+efuse_data_fail:
+	dma_free_coherent(dev, sizeof(struct xilinx_efuse),
+			  efuse, dma_addr);
+
+	return ret;
+}
+
+static int zynqmp_nvmem_read(void *context, unsigned int offset, void *val, size_t bytes)
 {
 	struct device *dev = context;
 	int ret;
+	int pufflag = 0;
 	int idcode;
 	int version;
 
-	ret = zynqmp_pm_get_chipid(&idcode, &version);
-	if (ret < 0)
-		return ret;
+	if (offset >= EFUSE_PUF_START_OFFSET && offset <= EFUSE_PUF_END_OFFSET)
+		pufflag = 1;
+
+	switch (offset) {
+	/* Soc version offset is zero */
+	case SOC_VERSION_OFFSET:
+		if (bytes != SOC_VER_SIZE)
+			return -EOPNOTSUPP;
+
+		ret = zynqmp_pm_get_chipid((u32 *)&idcode, (u32 *)&version);
+		if (ret < 0)
+			return ret;
+
+		dev_dbg(dev, "Read chipid val %x %x\n", idcode, version);
+		*(int *)val = version & SILICON_REVISION_MASK;
+		break;
+	/* Efuse offset starts from 0xc */
+	case EFUSE_START_OFFSET ... EFUSE_END_OFFSET:
+	case EFUSE_PUF_START_OFFSET ... EFUSE_PUF_END_OFFSET:
+		ret = zynqmp_efuse_access(context, offset, val,
+					  bytes, EFUSE_READ, pufflag);
+		break;
+	default:
+		*(u32 *)val = 0xDEADBEEF;
+		ret = 0;
+		break;
+	}
+
+	return ret;
+}
+
+static int zynqmp_nvmem_write(void *context,
+			      unsigned int offset, void *val, size_t bytes)
+{
+	int pufflag = 0;
+
+	if (offset < EFUSE_START_OFFSET || offset > EFUSE_PUF_END_OFFSET)
+		return -EOPNOTSUPP;
 
-	dev_dbg(dev, "Read chipid val %x %x\n", idcode, version);
-	*(int *)val = version & SILICON_REVISION_MASK;
+	if (offset >= EFUSE_PUF_START_OFFSET && offset <= EFUSE_PUF_END_OFFSET)
+		pufflag = 1;
 
-	return 0;
+	return zynqmp_efuse_access(context, offset,
+				   val, bytes, EFUSE_WRITE, pufflag);
 }
 
 static const struct of_device_id zynqmp_nvmem_match[] = {
@@ -45,11 +211,11 @@ static int zynqmp_nvmem_probe(struct platform_device *pdev)
 	econfig.name = "zynqmp-nvmem";
 	econfig.owner = THIS_MODULE;
 	econfig.word_size = 1;
-	econfig.size = 1;
+	econfig.size = ZYNQMP_NVMEM_SIZE;
 	econfig.dev = dev;
 	econfig.add_legacy_fixed_of_cells = true;
-	econfig.read_only = true;
 	econfig.reg_read = zynqmp_nvmem_read;
+	econfig.reg_write = zynqmp_nvmem_write;
 
 	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &econfig));
 }