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From:   Thomas Petazzoni <thomas.petazzoni@bootlin.com>
To:     Bin Liu <b-liu@ti.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tony Lindgren <tony@atomide.com>
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        alexandre.belloni@bootlin.com,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        stable@vger.kernel.org
Subject: [PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling
Date:   Fri, 28 May 2021 16:04:46 +0200
Message-Id: <20210528140446.278076-1-thomas.petazzoni@bootlin.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In commit 92af4fc6ec33 ("usb: musb: Fix suspend with devices
connected for a64"), the logic to support the
MUSB_QUIRK_B_DISCONNECT_99 quirk was modified to only conditionally
schedule the musb->irq_work delayed work.

This commit badly breaks ECM Gadget on AM335X. Indeed, with this
commit, one can observe massive packet loss:

$ ping 192.168.0.100
...
15 packets transmitted, 3 received, 80% packet loss, time 14316ms

Reverting this commit brings back a properly functioning ECM
Gadget. An analysis of the commit seems to indicate that a mistake was
made: the previous code was not falling through into the
MUSB_QUIRK_B_INVALID_VBUS_91, but now it is, unless the condition is
taken.

Changing the logic to be as it was before the problematic commit *and*
only conditionally scheduling musb->irq_work resolves the regression:

$ ping 192.168.0.100
...
64 packets transmitted, 64 received, 0% packet loss, time 64475ms

Fixes: 92af4fc6ec33 ("usb: musb: Fix suspend with devices connected for a64")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: stable@vger.kernel.org
---
 drivers/usb/musb/musb_core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 8f09a387b773..4c8f0112481f 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -2009,9 +2009,8 @@ static void musb_pm_runtime_check_session(struct musb *musb)
 			schedule_delayed_work(&musb->irq_work,
 					      msecs_to_jiffies(1000));
 			musb->quirk_retries--;
-			break;
 		}
-		fallthrough;
+		break;
 	case MUSB_QUIRK_B_INVALID_VBUS_91:
 		if (musb->quirk_retries && !musb->flush_irq_work) {
 			musb_dbg(musb,
-- 
2.31.1