net: mvpp2: use round-robin scheduling for TX queues on the same CPU

This commit allows each TXQ to be picked in a round-robin fashion by
the PPv2 transmit scheduling mechanism. This is opposed to the default
behaviour that prioritizes the highest numbered queues.

Suggested-by: Yan Markman <ymarkman@marvell.com>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2/mvpp2.h

@@ -331,6 +331,7 @@
 #define     MVPP2_TXP_SCHED_ENQ_MASK		0xff
 #define     MVPP2_TXP_SCHED_DISQ_OFFSET		8
 #define MVPP2_TXP_SCHED_CMD_1_REG		0x8010
+#define MVPP2_TXP_SCHED_FIXED_PRIO_REG		0x8014
 #define MVPP2_TXP_SCHED_PERIOD_REG		0x8018
 #define MVPP2_TXP_SCHED_MTU_REG			0x801c
 #define     MVPP2_TXP_MTU_MAX			0x7FFFF

drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c

@@ -1448,6 +1448,9 @@ static void mvpp2_defaults_set(struct mvpp2_port *port)
 		    tx_port_num);
 	mvpp2_write(port->priv, MVPP2_TXP_SCHED_CMD_1_REG, 0);
 
+	/* Set TXQ scheduling to Round-Robin */
+	mvpp2_write(port->priv, MVPP2_TXP_SCHED_FIXED_PRIO_REG, 0);
+
 	/* Close bandwidth for all queues */
 	for (queue = 0; queue < MVPP2_MAX_TXQ; queue++) {
 		ptxq = mvpp2_txq_phys(port->id, queue);