-/* Some registers, like VLANn_CTRL, should always be written in 64-bit, even if
- * you are to write only the lower / upper 32 bits.
+/* Some registers, like VLANn_CTRL, should always be written in chunks, even if
+ * you only want to write parts of 32 bits.
  *
- * There is no such restriction for reading, but we still provide 64-bit read
- * wrappers so that we always handle u64 values.
+ * There is no such restriction for reading, but we still provide multi-chunk
+ * read wrappers so that we can handle them consistently.
  */
 
-static int yt921x_reg64_read(struct yt921x_priv *priv, u32 reg, u64 *valp)
+static int
+yt921x_longreg_read(struct yt921x_priv *priv, u32 reg, u32 *vals,
+		    unsigned int span)

Just looking at this, it is not obvious what units span is. Many bulk
read operations takes bytes, even if the underlying code works in
words. I would probably rename span to something like num_u32.

I would also keep yt921x_reg64_read, yt921x_reg64_write,
yt921x_reg64_update_bits() and just makes them wrappers which call
yt921x_longreg_read(). 

-static int
-yt921x_vlan_del(struct yt921x_priv *priv, int port, u16 vid)
+static int yt921x_vlan_del(struct yt921x_priv *priv, int port, u16 vid)
 {
-	u64 mask64;
+	u32 masks[YT921X_VLAN_CTRL_S];
 
-	mask64 = YT921X_VLAN_CTRL_PORTS(port) |
-		 YT921X_VLAN_CTRL_UNTAG_PORTn(port);
+	masks[0] = YT921X_VLAN_CTRLa_PORTn(port);
+	masks[1] = YT921X_VLAN_CTRLb_UNTAG_PORTn(port);
 
-	return yt921x_reg64_clear_bits(priv, YT921X_VLANn_CTRL(vid), mask64);
+	return yt921x_longreg_clear_bits(priv, YT921X_VLANn_CTRL(vid), masks,
+					 YT921X_VLAN_CTRL_S);

By keeping the names, you don't need changes like this. And
yt921x_reg64_clear_bits() is much more obvious than
yt921x_longreg_clear_bits(). And the patch will be much smaller.

	Andrew