All the tables of NETC switch are managed through the command BD ring,
but unlike ENETC, the switch has two command BD rings, if the current
ring is busy, the switch driver can switch to another ring to manage
the table. Currently, the NTMP driver does not support multiple rings.
Therefore, netc_select_cbdr() is added to select a appropriate ring to
execute the command for the switch.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
---
 drivers/net/ethernet/freescale/enetc/ntmp.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/ntmp.c b/drivers/net/ethernet/freescale/enetc/ntmp.c
index 960d5be8ec42..5679b866af48 100644
--- a/drivers/net/ethernet/freescale/enetc/ntmp.c
+++ b/drivers/net/ethernet/freescale/enetc/ntmp.c
@@ -125,12 +125,21 @@ static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd)
 	u16 status;
 	u32 val;
 
-	/* Currently only i.MX95 ENETC is supported, and it only has one
-	 * command BD ring
+	for (i = 0; i < user->cbdr_num; i++) {
+		cbdr = &user->ring[i];
+		if (spin_trylock_bh(&cbdr->ring_lock))
+			break;
+	}
+
+	/* If all command BD rings are locked, we need to select
+	 * one of them and wait for it.
 	 */
-	cbdr = &user->ring[0];
+	if (i == user->cbdr_num) {
+		int cpu = raw_smp_processor_id();
 
-	spin_lock_bh(&cbdr->ring_lock);
+		cbdr = &user->ring[cpu % user->cbdr_num];
+		spin_lock_bh(&cbdr->ring_lock);
+	}
 
 	if (unlikely(!ntmp_get_free_cbd_num(cbdr)))
 		ntmp_clean_cbdr(cbdr);
-- 
2.34.1