kernel: fix mtk_eth_soc throughput regressions on gigabit PHY ports

Fixes issues on MT7621 and MT7623 switch ports, and PHY ports on all SoC

Signed-off-by: Felix Fietkau <nbd@nbd.name>

1 files changed, 42 insertions, 0 deletions

diff --git a/target/linux/generic/pending-5.15/732-03-net-ethernet-mtk_eth_soc-fix-remaining-throughput-re.patch b/target/linux/generic/pending-5.15/732-03-net-ethernet-mtk_eth_soc-fix-remaining-throughput-re.patch
new file mode 100644
index 0000000000..0aa9382b6b
--- /dev/null
+++ b/target/linux/generic/pending-5.15/732-03-net-ethernet-mtk_eth_soc-fix-remaining-throughput-re.patch
@@ -0,0 +1,42 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 29 Mar 2023 16:02:54 +0200
+Subject: [PATCH] net: ethernet: mtk_eth_soc: fix remaining throughput
+ regression
+
+Based on further tests, it seems that the QDMA shaper is not able to
+perform shaping close to the MAC link rate without throughput loss.
+This cannot be compensated by increasing the shaping rate, so it seems
+to be an internal limit.
+
+Fix the remaining throughput regression by detecting that condition and
+limiting shaping to ports with lower link speed.
+
+This patch intentionally ignores link speed gain from TRGMII, because
+even on such links, shaping to 1000 Mbit/s incurs some throughput
+degradation.
+
+Fixes: f63959c7eec3 ("net: ethernet: mtk_eth_soc: implement multi-queue support for per-port queues")
+Reported-by: Frank Wunderlich <frank-w@public-files.de>
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
++++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+@@ -667,6 +667,7 @@ static void mtk_mac_link_up(struct phyli
+ 		 MAC_MCR_FORCE_RX_FC);
+ 
+ 	/* Configure speed */
++	mac->speed = speed;
+ 	switch (speed) {
+ 	case SPEED_2500:
+ 	case SPEED_1000:
+@@ -3145,6 +3146,9 @@ found:
+ 	if (dp->index >= MTK_QDMA_NUM_QUEUES)
+ 		return NOTIFY_DONE;
+ 
++	if (mac->speed > 0 && mac->speed <= s.base.speed)
++		s.base.speed = 0;
++
+ 	mtk_set_queue_speed(eth, dp->index + 3, s.base.speed);
+ 
+ 	return NOTIFY_DONE;