[PATCH 5.12 094/173] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling

[Greg Kroah-Hartman]

From: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>

commit b65ba0c362be665192381cc59e3ac3ef6f0dd1e1 upstream.

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")
Cc: stable@xxxxxxxxxxxxxxx
Tested-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Tested-by: Drew Fustini <drew@xxxxxxxxxxxxxxx>
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210528140446.278076-1-thomas.petazzoni@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/musb/musb_core.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -2009,9 +2009,8 @@ static void musb_pm_runtime_check_sessio
 			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,