FAILED: patch "[PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b65ba0c362be665192381cc59e3ac3ef6f0dd1e1 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <[email protected]>
Date: Fri, 28 May 2021 16:04:46 +0200
Subject: [PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling

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

index 8f09a387b773..4c8f0112481f 100644
@@ -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,