[PATCH v2] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1

From: Pawel Laszczak <pawell@cadence.com>
To: <peter.chen@kernel.org>
Cc: <gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	Pawel Laszczak <pawell@cadence.com>, <stable@vger.kernel.org>
Subject: [PATCH v2] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1
Date: Mon, 24 Oct 2022 10:04:35 -0400	[thread overview]
Message-ID: <1666620275-139704-1-git-send-email-pawell@cadence.com> (raw)

Patch modifies the TD_SIZE in TRB before ZLP TRB.
The TD_SIZE in TRB before ZLP TRB must be set to 1 to force
processing ZLP TRB by controller.

cc: <stable@vger.kernel.org>
Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
Signed-off-by: Pawel Laszczak <pawell@cadence.com>

---
Changelog:
v2:
- returned value for last TRB must be 0

 drivers/usb/cdns3/cdnsp-ring.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdnsp-ring.c b/drivers/usb/cdns3/cdnsp-ring.c
index 04dfcaa08dc4..aa79bce89d8a 100644
--- a/drivers/usb/cdns3/cdnsp-ring.c
+++ b/drivers/usb/cdns3/cdnsp-ring.c
@@ -1769,8 +1769,13 @@ static u32 cdnsp_td_remainder(struct cdnsp_device *pdev,
 
 	/* One TRB with a zero-length data packet. */
 	if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
-	    trb_buff_len == td_total_len)
+	    trb_buff_len == td_total_len) {
+		/* Before ZLP driver needs set TD_SIZE=1. */
+		if (more_trbs_coming)
+			return 1;
+
 		return 0;
+	}
 
 	maxp = usb_endpoint_maxp(preq->pep->endpoint.desc);
 	total_packet_count = DIV_ROUND_UP(td_total_len, maxp);
-- 
2.25.1

