wifi: rt2x00: add nvmem eeprom support

Some embedded platforms have eeproms located in flash. Add nvmem support
to handle this. Support is added for PCI and SOC backends.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://patch.msgid.link/20251027180639.3797-1-rosenp@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

@@ -24,6 +24,7 @@
 #include <linux/crc-ccitt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/nvmem-consumer.h>
 #include <linux/slab.h>
 
 #include "rt2x00.h"
@@ -10962,6 +10963,36 @@ int rt2800_read_eeprom_efuse(struct rt2x00_dev *rt2x00dev)
 }
 EXPORT_SYMBOL_GPL(rt2800_read_eeprom_efuse);
 
+int rt2800_read_eeprom_nvmem(struct rt2x00_dev *rt2x00dev)
+{
+	struct device_node *np = rt2x00dev->dev->of_node;
+	unsigned int len = rt2x00dev->ops->eeprom_size;
+	struct nvmem_cell *cell;
+	const void *data;
+	size_t retlen;
+
+	cell = of_nvmem_cell_get(np, "eeprom");
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	data = nvmem_cell_read(cell, &retlen);
+	nvmem_cell_put(cell);
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	if (retlen != len) {
+		dev_err(rt2x00dev->dev, "invalid eeprom size, required: 0x%04x\n", len);
+		kfree(data);
+		return -EINVAL;
+	}
+
+	memcpy(rt2x00dev->eeprom, data, len);
+	kfree(data);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rt2800_read_eeprom_nvmem);
+
 static u8 rt2800_get_txmixer_gain_24g(struct rt2x00_dev *rt2x00dev)
 {
 	u16 word;

drivers/net/wireless/ralink/rt2x00/rt2800lib.h

@@ -248,6 +248,8 @@ void rt2800_disable_radio(struct rt2x00_dev *rt2x00dev);
 int rt2800_efuse_detect(struct rt2x00_dev *rt2x00dev);
 int rt2800_read_eeprom_efuse(struct rt2x00_dev *rt2x00dev);
 
+int rt2800_read_eeprom_nvmem(struct rt2x00_dev *rt2x00dev);
+
 int rt2800_probe_hw(struct rt2x00_dev *rt2x00dev);
 
 void rt2800_get_key_seq(struct ieee80211_hw *hw,

drivers/net/wireless/ralink/rt2x00/rt2800pci.c

@@ -278,6 +278,9 @@ static int rt2800pci_read_eeprom(struct rt2x00_dev *rt2x00dev)
 {
 	int retval;
 
+	if (!rt2800_read_eeprom_nvmem(rt2x00dev))
+		return 0;
+
 	if (rt2800pci_efuse_detect(rt2x00dev))
 		retval = rt2800pci_read_eeprom_efuse(rt2x00dev);
 	else

drivers/net/wireless/ralink/rt2x00/rt2800soc.c

@@ -92,8 +92,12 @@ static int rt2800soc_set_device_state(struct rt2x00_dev *rt2x00dev,
 
 static int rt2800soc_read_eeprom(struct rt2x00_dev *rt2x00dev)
 {
-	void __iomem *base_addr = ioremap(0x1F040000, EEPROM_SIZE);
+	void __iomem *base_addr;
 
+	if (!rt2800_read_eeprom_nvmem(rt2x00dev))
+		return 0;
+
+	base_addr = ioremap(0x1F040000, EEPROM_SIZE);
 	if (!base_addr)
 		return -ENOMEM;