linux-kernel - [PATCH net-next] net: wwan: mhi_wwan_mbim: Silence sequence number glitch errors

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Message-Id: <20250212-mhi-wwan-mbim-sequence-glitch-v1-1-503735977cbd@linaro.org>
Date: Wed, 12 Feb 2025 12:15:35 +0100
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Loic Poulain <loic.poulain@...aro.org>, 
 Sergey Ryazanov <ryazanov.s.a@...il.com>, 
 Johannes Berg <johannes@...solutions.net>, 
 Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Johan Hovold <johan@...nel.org>, Abel Vesa <abel.vesa@...aro.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH net-next] net: wwan: mhi_wwan_mbim: Silence sequence number
 glitch errors

When using the Qualcomm X55 modem on the ThinkPad X13s, the kernel log is
constantly being filled with errors related to a "sequence number glitch",
e.g.:

	[ 1903.284538] sequence number glitch prev=16 curr=0
	[ 1913.812205] sequence number glitch prev=50 curr=0
	[ 1923.698219] sequence number glitch prev=142 curr=0
	[ 2029.248276] sequence number glitch prev=1555 curr=0
	[ 2046.333059] sequence number glitch prev=70 curr=0
	[ 2076.520067] sequence number glitch prev=272 curr=0
	[ 2158.704202] sequence number glitch prev=2655 curr=0
	[ 2218.530776] sequence number glitch prev=2349 curr=0
	[ 2225.579092] sequence number glitch prev=6 curr=0

Internet connectivity is working fine, so this error seems harmless. It
looks like modem does not preserve the sequence number when entering low
power state; the amount of errors depends on how actively the modem is
being used.

A similar issue has also been seen on USB-based MBIM modems [1]. However,
in cdc_ncm.c the "sequence number glitch" message is a debug message
instead of an error. Apply the same to the mhi_wwan_mbim.c driver to
silence these errors when using the modem.

[1]: https://lists.freedesktop.org/archives/libmbim-devel/2016-November/000781.html

Signed-off-by: Stephan Gerhold <stephan.gerhold@...aro.org>
---
 drivers/net/wwan/mhi_wwan_mbim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wwan/mhi_wwan_mbim.c b/drivers/net/wwan/mhi_wwan_mbim.c
index d5a9360323d29df4b6665bef0949e017c90876a4..8755c5e6a65b302c9ba2fe463e9eac58d956eaff 100644
--- a/drivers/net/wwan/mhi_wwan_mbim.c
+++ b/drivers/net/wwan/mhi_wwan_mbim.c
@@ -220,7 +220,7 @@ static int mbim_rx_verify_nth16(struct mhi_mbim_context *mbim, struct sk_buff *s
 	if (mbim->rx_seq + 1 != le16_to_cpu(nth16->wSequence) &&
 	    (mbim->rx_seq || le16_to_cpu(nth16->wSequence)) &&
 	    !(mbim->rx_seq == 0xffff && !le16_to_cpu(nth16->wSequence))) {
-		net_err_ratelimited("sequence number glitch prev=%d curr=%d\n",
+		net_dbg_ratelimited("sequence number glitch prev=%d curr=%d\n",
 				    mbim->rx_seq, le16_to_cpu(nth16->wSequence));
 	}
 	mbim->rx_seq = le16_to_cpu(nth16->wSequence);

---
base-commit: 4e41231249f4083a095085ff86e317e29313c2c3
change-id: 20250206-mhi-wwan-mbim-sequence-glitch-cdbd2db5b3bb

Best regards,
-- 
Stephan Gerhold <stephan.gerhold@...aro.org>