linux-kernel - [PATCH] Revert "usb: dwc3: gadget: always decrement by 1"

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Message-Id: <fdd09d57d46bf407999387fb32e5c716dcc0b2de.1472262087.git.johnyoun@synopsys.com>
Date:   Fri, 26 Aug 2016 18:43:01 -0700
From:   John Youn <johnyoun@...opsys.com>
To:     linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "usb: dwc3: gadget: always decrement by 1"

This reverts commit 6f8245b4e37c ("usb: dwc3: gadget: always decrement
by 1").

We can't always decrement this value.

We should decrement only if the calculation of free slots results in a
LINK TRB being among one of the free slots (dequeue < enqueue).

Otherwise, if the LINK TRB is not among the free slots then it should
not be decremented.

Signed-off-by: John Youn <johnyoun@...opsys.com>
---
 drivers/usb/dwc3/gadget.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 7a8d3d8..122e64d 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -884,9 +884,12 @@ static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep)
 		return DWC3_TRB_NUM - 1;
 	}
 
-	trbs_left = dep->trb_dequeue - dep->trb_enqueue - 1;
+	trbs_left = dep->trb_dequeue - dep->trb_enqueue;
 	trbs_left &= (DWC3_TRB_NUM - 1);
 
+	if (dep->trb_dequeue < dep->trb_enqueue)
+		trbs_left--;
+
 	return trbs_left;
 }
 
-- 
2.9.0