net: dsa: mv88e6xxx: protect FID registers access

Only switch families with 4096 address databases have dedicated FID
registers for ATU and VTU operations.

Factorize the access to the GLOBAL_ATU_FID register and introduce a
mv88e6xxx_has_fid_reg() helper function to protect the access to
GLOBAL_ATU_FID and GLOBAL_VTU_FID.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx.c

@@ -482,6 +482,16 @@ static bool mv88e6xxx_6352_family(struct dsa_switch *ds)
 	return false;
 }
 
+static bool mv88e6xxx_has_fid_reg(struct dsa_switch *ds)
+{
+	/* Does the device have dedicated FID registers for ATU and VTU ops? */
+	if (mv88e6xxx_6097_family(ds) || mv88e6xxx_6165_family(ds) ||
+	    mv88e6xxx_6351_family(ds) || mv88e6xxx_6352_family(ds))
+		return true;
+
+	return false;
+}
+
 static bool mv88e6xxx_has_stu(struct dsa_switch *ds)
 {
 	/* Does the device have STU and dedicated SID registers for VTU ops? */
@@ -961,10 +971,16 @@ int mv88e6xxx_set_eee(struct dsa_switch *ds, int port,
 	return ret;
 }
 
-static int _mv88e6xxx_atu_cmd(struct dsa_switch *ds, u16 cmd)
+static int _mv88e6xxx_atu_cmd(struct dsa_switch *ds, u16 fid, u16 cmd)
 {
 	int ret;
 
+	if (mv88e6xxx_has_fid_reg(ds)) {
+		ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_ATU_FID, fid);
+		if (ret < 0)
+			return ret;
+	}
+
 	ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_ATU_OP, cmd);
 	if (ret < 0)
 		return ret;
@@ -1011,19 +1027,14 @@ static int _mv88e6xxx_atu_flush_move(struct dsa_switch *ds,
 		return err;
 
 	if (entry->fid) {
-		err = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_ATU_FID,
-					   entry->fid);
-		if (err)
-			return err;
-
 		op = static_too ? GLOBAL_ATU_OP_FLUSH_MOVE_ALL_DB :
 			GLOBAL_ATU_OP_FLUSH_MOVE_NON_STATIC_DB;
 	} else {
 		op = static_too ? GLOBAL_ATU_OP_FLUSH_MOVE_ALL :
 			GLOBAL_ATU_OP_FLUSH_MOVE_NON_STATIC;
 	}
 
-	return _mv88e6xxx_atu_cmd(ds, op);
+	return _mv88e6xxx_atu_cmd(ds, entry->fid, op);
 }
 
 static int _mv88e6xxx_atu_flush(struct dsa_switch *ds, u16 fid, bool static_too)
@@ -1331,8 +1342,7 @@ static int _mv88e6xxx_vtu_getnext(struct dsa_switch *ds,
 		if (ret < 0)
 			return ret;
 
-		if (mv88e6xxx_6097_family(ds) || mv88e6xxx_6165_family(ds) ||
-		    mv88e6xxx_6351_family(ds) || mv88e6xxx_6352_family(ds)) {
+		if (mv88e6xxx_has_fid_reg(ds)) {
 			ret = _mv88e6xxx_reg_read(ds, REG_GLOBAL,
 						  GLOBAL_VTU_FID);
 			if (ret < 0)
@@ -1429,7 +1439,9 @@ static int _mv88e6xxx_vtu_loadpurge(struct dsa_switch *ds,
 		ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_VTU_SID, reg);
 		if (ret < 0)
 			return ret;
+	}
 
+	if (mv88e6xxx_has_fid_reg(ds)) {
 		reg = entry->fid & GLOBAL_VTU_FID_MASK;
 		ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_VTU_FID, reg);
 		if (ret < 0)
@@ -1976,11 +1988,7 @@ static int _mv88e6xxx_atu_load(struct dsa_switch *ds,
 	if (ret < 0)
 		return ret;
 
-	ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_ATU_FID, entry->fid);
-	if (ret < 0)
-		return ret;
-
-	return _mv88e6xxx_atu_cmd(ds, GLOBAL_ATU_OP_LOAD_DB);
+	return _mv88e6xxx_atu_cmd(ds, entry->fid, GLOBAL_ATU_OP_LOAD_DB);
 }
 
 static int _mv88e6xxx_port_fdb_load(struct dsa_switch *ds, int port,
@@ -2063,11 +2071,7 @@ static int _mv88e6xxx_atu_getnext(struct dsa_switch *ds, u16 fid,
 	if (ret < 0)
 		return ret;
 
-	ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_ATU_FID, fid);
-	if (ret < 0)
-		return ret;
-
-	ret = _mv88e6xxx_atu_cmd(ds, GLOBAL_ATU_OP_GET_NEXT_DB);
+	ret = _mv88e6xxx_atu_cmd(ds, fid, GLOBAL_ATU_OP_GET_NEXT_DB);
 	if (ret < 0)
 		return ret;