net: dsa: mv88e6xxx: add helper to disable ports

Before resetting a switch, the ports should be set to the Disabled state
and the transmit queues should be drained.

Add an helper to explicit that.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -2356,17 +2356,11 @@ static void mv88e6xxx_port_bridge_leave(struct dsa_switch *ds, int port)
 	mutex_unlock(&chip->reg_lock);
 }
 
-static int mv88e6xxx_switch_reset(struct mv88e6xxx_chip *chip)
+static int mv88e6xxx_disable_ports(struct mv88e6xxx_chip *chip)
 {
-	bool ppu_active = mv88e6xxx_has(chip, MV88E6XXX_FLAG_PPU_ACTIVE);
-	u16 is_reset = (ppu_active ? 0x8800 : 0xc800);
-	struct gpio_desc *gpiod = chip->reset;
-	unsigned long timeout;
-	u16 reg;
-	int err;
-	int i;
+	int i, err;
 
-	/* Set all ports to the disabled state. */
+	/* Set all ports to the Disabled state */
 	for (i = 0; i < mv88e6xxx_num_ports(chip); i++) {
 		err = mv88e6xxx_port_set_state(chip, i,
 					       PORT_CONTROL_STATE_DISABLED);
@@ -2374,9 +2368,27 @@ static int mv88e6xxx_switch_reset(struct mv88e6xxx_chip *chip)
 			return err;
 	}
 
-	/* Wait for transmit queues to drain. */
+	/* Wait for transmit queues to drain,
+	 * i.e. 2ms for a maximum frame to be transmitted at 10 Mbps.
+	 */
 	usleep_range(2000, 4000);
 
+	return 0;
+}
+
+static int mv88e6xxx_switch_reset(struct mv88e6xxx_chip *chip)
+{
+	bool ppu_active = mv88e6xxx_has(chip, MV88E6XXX_FLAG_PPU_ACTIVE);
+	u16 is_reset = (ppu_active ? 0x8800 : 0xc800);
+	struct gpio_desc *gpiod = chip->reset;
+	unsigned long timeout;
+	u16 reg;
+	int err;
+
+	err = mv88e6xxx_disable_ports(chip);
+	if (err)
+		return err;
+
 	/* If there is a gpio connected to the reset pin, toggle it */
 	if (gpiod) {
 		gpiod_set_value_cansleep(gpiod, 1);