wifi: mt76: add support for providing eeprom in nvmem cells

Add support for providing eeprom in nvmem cells by adding nvmem cell as
an alternative source for mt76_get_of_eeprom().

Nvmem cells will follow standard nvmem cell definition and needs to be
called 'eeprom' to be correctly identified.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/eeprom.c

@@ -6,6 +6,7 @@
 #include <linux/of_net.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
+#include <linux/nvmem-consumer.h>
 #include <linux/etherdevice.h>
 #include "mt76.h"
 
@@ -105,6 +106,37 @@ static int mt76_get_of_epprom_from_mtd(struct mt76_dev *dev, void *eep, int offs
 #endif
 }
 
+static int mt76_get_of_epprom_from_nvmem(struct mt76_dev *dev, void *eep, int len)
+{
+	struct device_node *np = dev->dev->of_node;
+	struct nvmem_cell *cell;
+	const void *data;
+	size_t retlen;
+	int ret = 0;
+
+	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) {
+		ret = -EINVAL;
+		goto exit;
+	}
+
+	memcpy(eep, data, len);
+
+exit:
+	kfree(data);
+
+	return ret;
+}
+
 int mt76_get_of_eeprom(struct mt76_dev *dev, void *eep, int offset, int len)
 {
 	struct device_node *np = dev->dev->of_node;
@@ -117,7 +149,11 @@ int mt76_get_of_eeprom(struct mt76_dev *dev, void *eep, int offset, int len)
 	if (!ret)
 		return 0;
 
-	return mt76_get_of_epprom_from_mtd(dev, eep, offset, len);
+	ret = mt76_get_of_epprom_from_mtd(dev, eep, offset, len);
+	if (!ret)
+		return 0;
+
+	return mt76_get_of_epprom_from_nvmem(dev, eep, len);
 }
 EXPORT_SYMBOL_GPL(mt76_get_of_eeprom);