linux-kernel - [PATCH v2] thunderbolt: Check whether bandwidth request needs asymmetric mode before check whether it can be done

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Message-ID: <20250628123453.770988-1-zhangjianrong5@huawei.com>
Date: Sat, 28 Jun 2025 20:34:53 +0800
From: zhangjianrong <zhangjianrong5@...wei.com>
To: <andreas.noever@...il.com>, <michael.jamet@...el.com>,
	<mika.westerberg@...ux.intel.com>, <YehezkelShB@...il.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <guhengsheng@...ilicon.com>, <caiyadong@...wei.com>,
	<xuetao09@...wei.com>, <lixinghang1@...wei.com>
Subject: [PATCH v2] thunderbolt: Check whether bandwidth request needs asymmetric mode before check whether it can be done

Current implementation may cause allocation failures in
tb_alloc_dp_bandwidth() in some cases. This will happen
when requesting downstream bandwidth while total upstream
bandwidth usage on the link exceeds TB_ASYM_MIN (36 Gbps).
tb_configure_asym() will return -ENOBUFS while asymmetric
mode isn't necessary.

Fixes: 3e36528c1127 ("thunderbolt: Configure asymmetric link if needed and bandwidth allows")
Signed-off-by: zhangjianrong <zhangjianrong5@...wei.com>
---
v2: update subject and commit message
v1: initial submission

 drivers/thunderbolt/tb.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index a7c6919fbf97..558455d9716b 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1039,6 +1039,9 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 			break;
 
 		if (downstream) {
+			/* Does consumed + requested exceed the threshold */
+			if (consumed_down + requested_down < asym_threshold)
+				continue;
 			/*
 			 * Downstream so make sure upstream is within the 36G
 			 * (40G - guard band 10%), and the requested is above
@@ -1048,20 +1051,17 @@ static int tb_configure_asym(struct tb *tb, struct tb_port *src_port,
 				ret = -ENOBUFS;
 				break;
 			}
-			/* Does consumed + requested exceed the threshold */
-			if (consumed_down + requested_down < asym_threshold)
-				continue;
 
 			width_up = TB_LINK_WIDTH_ASYM_RX;
 			width_down = TB_LINK_WIDTH_ASYM_TX;
 		} else {
 			/* Upstream, the opposite of above */
+			if (consumed_up + requested_up < asym_threshold)
+				continue;
 			if (consumed_down + requested_down >= TB_ASYM_MIN) {
 				ret = -ENOBUFS;
 				break;
 			}
-			if (consumed_up + requested_up < asym_threshold)
-				continue;
 
 			width_up = TB_LINK_WIDTH_ASYM_TX;
 			width_down = TB_LINK_WIDTH_ASYM_RX;
-- 
2.34.1