linux-kernel - [PATCH] usb: cdnsp: fix issue with ZLP

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Date:   Wed, 19 Oct 2022 02:07:17 -0400
From:   Pawel Laszczak <pawell@...ence.com>
To:     <peter.chen@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Pawel Laszczak <pawell@...ence.com>, <stable@...r.kernel.org>
Subject: [PATCH] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1

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@...r.kernel.org>
Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
Signed-off-by: Pawel Laszczak <pawell@...ence.com>
---
 drivers/usb/cdns3/cdnsp-ring.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/cdns3/cdnsp-ring.c b/drivers/usb/cdns3/cdnsp-ring.c
index 794e413800ae..4809d0e894bb 100644
--- a/drivers/usb/cdns3/cdnsp-ring.c
+++ b/drivers/usb/cdns3/cdnsp-ring.c
@@ -1765,18 +1765,19 @@ static u32 cdnsp_td_remainder(struct cdnsp_device *pdev,
 			      struct cdnsp_request *preq,
 			      bool more_trbs_coming)
 {
-	u32 maxp, total_packet_count;
-
-	/* One TRB with a zero-length data packet. */
-	if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
-	    trb_buff_len == td_total_len)
-		return 0;
+	u32 maxp, total_packet_count, remainder;
 
 	maxp = usb_endpoint_maxp(preq->pep->endpoint.desc);
 	total_packet_count = DIV_ROUND_UP(td_total_len, maxp);
 
 	/* Queuing functions don't count the current TRB into transferred. */
-	return (total_packet_count - ((transferred + trb_buff_len) / maxp));
+	remainder = (total_packet_count - ((transferred + trb_buff_len) / maxp));
+
+	/* Before ZLP driver needs set TD_SIZE=1. */
+	if (!remainder && more_trbs_coming)
+		remainder = 1;
+
+	return remainder;
 }
 
 static int cdnsp_align_td(struct cdnsp_device *pdev,
-- 
2.25.1