linux-kernel - [PATCH v2] net: thunderbolt: Enable end-to-end flow control also in transmit

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Message-ID: <20250628093813.647005-1-zhangjianrong5@huawei.com>
Date: Sat, 28 Jun 2025 17:38:13 +0800
From: zhangjianrong <zhangjianrong5@...wei.com>
To: <michael.jamet@...el.com>, <mika.westerberg@...ux.intel.com>,
	<YehezkelShB@...il.com>, <andrew+netdev@...n.ch>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <guhengsheng@...ilicon.com>, <caiyadong@...wei.com>,
	<xuetao09@...wei.com>, <lixinghang1@...wei.com>
Subject: [PATCH v2] net: thunderbolt: Enable end-to-end flow control also in transmit

According to USB4 specification, if E2E flow control is disabled for
the Transmit Descriptor Ring, the Host Interface Adapter Layer shall
not require any credits to be available before transmitting a Tunneled
Packet from this Transmit Descriptor Ring, so e2e flow control should
be enabled in both directions.

Signed-off-by: zhangjianrong <zhangjianrong5@...wei.com>
---
v2: update subject and commit message
v1: initial submission

 drivers/net/thunderbolt/main.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 0a53ec293d04..643cf67840b5 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -924,8 +924,12 @@ static int tbnet_open(struct net_device *dev)
 
 	netif_carrier_off(dev);
 
-	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE,
-				RING_FLAG_FRAME);
+	flags = RING_FLAG_FRAME;
+	/* Only enable full E2E if the other end supports it too */
+	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
+		flags |= RING_FLAG_E2E;
+
+	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags);
 	if (!ring) {
 		netdev_err(dev, "failed to allocate Tx ring\n");
 		return -ENOMEM;
@@ -944,11 +948,6 @@ static int tbnet_open(struct net_device *dev)
 	sof_mask = BIT(TBIP_PDF_FRAME_START);
 	eof_mask = BIT(TBIP_PDF_FRAME_END);
 
-	flags = RING_FLAG_FRAME;
-	/* Only enable full E2E if the other end supports it too */
-	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
-		flags |= RING_FLAG_E2E;
-
 	ring = tb_ring_alloc_rx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags,
 				net->tx_ring.ring->hop, sof_mask,
 				eof_mask, tbnet_start_poll, net);
-- 
2.34.1