linux-kernel - [PATCH] usb: cdns3: fix incorrect handling TRB

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Date:   Thu, 25 Aug 2022 08:22:07 +0200
From:   Pawel Laszczak <pawell@...ence.com>
To:     <peter.chen@...nel.org>
CC:     <linux-usb@...r.kernel.org>, <gregkh@...uxfoundation.org>,
        <felipe.balbi@...ux.intel.com>, <rogerq@...nel.org>,
        <a-govindraju@...com>, <linux-kernel@...r.kernel.org>,
        Pawel Laszczak <pawell@...ence.com>, <stable@...r.kernel.org>
Subject: [PATCH] usb: cdns3: fix incorrect handling TRB_SMM flag for ISOC transfer

The TRB_SMM flag indicates that DMA has completed the TD service with
this TRB. Usually it’s a last TRB in TD. In case of ISOC transfer for
bInterval > 1 each ISOC transfer contains more than one TD associated
with usb request (one TD per ITP). In such case the TRB_SMM flag will
be set in every TD and driver will recognize the end of transfer after
processing the first TD with TRB_SMM. In result driver stops updating
request->actual and returns incorrect actual length.
To fix this issue driver additionally must check TRB_CHAIN which is not
used for isochronous transfers.

Fixes: 249f0a25e8be ("usb: cdns3: gadget: handle sg list use case at completion correctly")
cc: <stable@...r.kernel.org>
Signed-off-by: Pawel Laszczak <pawell@...ence.com>
---
 drivers/usb/cdns3/cdns3-gadget.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index fa8263951e63..a6618a922c61 100644
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -1529,7 +1529,8 @@ static void cdns3_transfer_completed(struct cdns3_device *priv_dev,
 						TRB_LEN(le32_to_cpu(trb->length));

 				if (priv_req->num_of_trb > 1 &&
-					le32_to_cpu(trb->control) & TRB_SMM)
+					le32_to_cpu(trb->control) & TRB_SMM &&
+					le32_to_cpu(trb->control) & TRB_CHAIN)
 					transfer_end = true;

 				cdns3_ep_inc_deq(priv_ep);
-- 
2.25.1