bnxt_en: Add support for user configured RSS key

Store the user configured or generated Toeplitz key in
bp->rss_hash_key.  The key stays constant across ifdown/ifup
unless updated by the user.
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20240205223202.25341-12-michael.chan@broadcom.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -4246,9 +4246,23 @@ static void bnxt_init_vnics(struct bnxt *bp)
 				u8 *key = (void *)vnic->rss_hash_key;
 				int k;
 
+				if (!bp->rss_hash_key_valid &&
+				    !bp->rss_hash_key_updated) {
+					get_random_bytes(bp->rss_hash_key,
+							 HW_HASH_KEY_SIZE);
+					bp->rss_hash_key_updated = true;
+				}
+
+				memcpy(vnic->rss_hash_key, bp->rss_hash_key,
+				       HW_HASH_KEY_SIZE);
+
+				if (!bp->rss_hash_key_updated)
+					continue;
+
+				bp->rss_hash_key_updated = false;
+				bp->rss_hash_key_valid = true;
+
 				bp->toeplitz_prefix = 0;
-				get_random_bytes(vnic->rss_hash_key,
-					      HW_HASH_KEY_SIZE);
 				for (k = 0; k < 8; k++) {
 					bp->toeplitz_prefix <<= 8;
 					bp->toeplitz_prefix |= key[k];

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -2222,6 +2222,10 @@ struct bnxt {
 #define BNXT_RSS_CAP_NEW_RSS_CAP		BIT(2)
 #define BNXT_RSS_CAP_RSS_TCAM			BIT(3)
 
+	u8			rss_hash_key[HW_HASH_KEY_SIZE];
+	u8			rss_hash_key_valid:1;
+	u8			rss_hash_key_updated:1;
+
 	u16			max_mtu;
 	u8			max_tc;
 	u8			max_lltc;	/* lossless TCs */

drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c

@@ -1755,8 +1755,10 @@ static int bnxt_set_rxfh(struct net_device *dev,
 	if (rxfh->hfunc && rxfh->hfunc != ETH_RSS_HASH_TOP)
 		return -EOPNOTSUPP;
 
-	if (rxfh->key)
-		return -EOPNOTSUPP;
+	if (rxfh->key) {
+		memcpy(bp->rss_hash_key, rxfh->key, HW_HASH_KEY_SIZE);
+		bp->rss_hash_key_updated = true;
+	}
 
 	if (rxfh->indir) {
 		u32 i, pad, tbl_size = bnxt_get_rxfh_indir_size(dev);