releases/6.1.149/net-fec-allow-disable-coalescing.patch

From e81e20541dee3dacf04cde9d430115dbafbdf73d Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Thu, 26 Jun 2025 15:44:02 +0200
Subject: net: fec: allow disable coalescing

From: Jonas Rebmann <jre@pengutronix.de>

[ Upstream commit b7ad21258f9e9a7f58b19595d5ceed2cde3bed68 ]

In the current implementation, IP coalescing is always enabled and
cannot be disabled.

As setting maximum frames to 0 or 1, or setting delay to zero implies
immediate delivery of single packets/IRQs, disable coalescing in
hardware in these cases.

This also guarantees that coalescing is never enabled with ICFT or ICTT
set to zero, a configuration that could lead to unpredictable behaviour
according to i.MX8MP reference manual.

Signed-off-by: Jonas Rebmann <jre@pengutronix.de>
Reviewed-by: Wei Fang <wei.fang@nxp.com>
Link: https://patch.msgid.link/20250626-fec_deactivate_coalescing-v2-1-0b217f2e80da@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/freescale/fec_main.c | 34 +++++++++++------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 4a513dba8f53..d10db5d6d226 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -2831,27 +2831,25 @@ static int fec_enet_us_to_itr_clock(struct net_device *ndev, int us)
 static void fec_enet_itr_coal_set(struct net_device *ndev)
 {
 	struct fec_enet_private *fep = netdev_priv(ndev);
-	int rx_itr, tx_itr;
+	u32 rx_itr = 0, tx_itr = 0;
+	int rx_ictt, tx_ictt;
 
-	/* Must be greater than zero to avoid unpredictable behavior */
-	if (!fep->rx_time_itr || !fep->rx_pkts_itr ||
-	    !fep->tx_time_itr || !fep->tx_pkts_itr)
-		return;
-
-	/* Select enet system clock as Interrupt Coalescing
-	 * timer Clock Source
-	 */
-	rx_itr = FEC_ITR_CLK_SEL;
-	tx_itr = FEC_ITR_CLK_SEL;
+	rx_ictt = fec_enet_us_to_itr_clock(ndev, fep->rx_time_itr);
+	tx_ictt = fec_enet_us_to_itr_clock(ndev, fep->tx_time_itr);
 
-	/* set ICFT and ICTT */
-	rx_itr |= FEC_ITR_ICFT(fep->rx_pkts_itr);
-	rx_itr |= FEC_ITR_ICTT(fec_enet_us_to_itr_clock(ndev, fep->rx_time_itr));
-	tx_itr |= FEC_ITR_ICFT(fep->tx_pkts_itr);
-	tx_itr |= FEC_ITR_ICTT(fec_enet_us_to_itr_clock(ndev, fep->tx_time_itr));
+	if (rx_ictt > 0 && fep->rx_pkts_itr > 1) {
+		/* Enable with enet system clock as Interrupt Coalescing timer Clock Source */
+		rx_itr = FEC_ITR_EN | FEC_ITR_CLK_SEL;
+		rx_itr |= FEC_ITR_ICFT(fep->rx_pkts_itr);
+		rx_itr |= FEC_ITR_ICTT(rx_ictt);
+	}
 
-	rx_itr |= FEC_ITR_EN;
-	tx_itr |= FEC_ITR_EN;
+	if (tx_ictt > 0 && fep->tx_pkts_itr > 1) {
+		/* Enable with enet system clock as Interrupt Coalescing timer Clock Source */
+		tx_itr = FEC_ITR_EN | FEC_ITR_CLK_SEL;
+		tx_itr |= FEC_ITR_ICFT(fep->tx_pkts_itr);
+		tx_itr |= FEC_ITR_ICTT(tx_ictt);
+	}
 
 	writel(tx_itr, fep->hwp + FEC_TXIC0);
 	writel(rx_itr, fep->hwp + FEC_RXIC0);
-- 
2.39.5