linux-kernel - [PATCH 5.4 070/168] usb: cdns3: gadget: toggle cycle bit before reset endpoint

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Date:   Tue, 10 Mar 2020 13:38:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Chen <peter.chen@....com>
Subject: [PATCH 5.4 070/168] usb: cdns3: gadget: toggle cycle bit before reset endpoint

From: Peter Chen <peter.chen@....com>

commit 4bf2dd65135a2d7fe202f7c10d65b51bcf645ac6 upstream.

If there are TRBs pending during reset endpoint operation, the
DMA will advance after reset operation, but it isn't expected,
since the data is not yet available (For OUT, the data is not
yet available). After the data is ready, there won't be any
interrupt since the EP_TRADDR already points to next TRB entry
and doorbell is not set.

To fix it, it toggles cycle bit before reset operation, and restores
it after reset, it could avoid unexpected DMA advance due to
cycle bit is for software during the endpoint reset operation.

Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: Peter Chen <peter.chen@....com>
Cc: stable <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20200219141455.23257-3-peter.chen@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/cdns3/gadget.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

--- a/drivers/usb/cdns3/gadget.c
+++ b/drivers/usb/cdns3/gadget.c
@@ -2152,11 +2152,21 @@ int __cdns3_gadget_ep_clear_halt(struct
 {
 	struct cdns3_device *priv_dev = priv_ep->cdns3_dev;
 	struct usb_request *request;
+	struct cdns3_request *priv_req;
+	struct cdns3_trb *trb = NULL;
 	int ret;
 	int val;
 
 	trace_cdns3_halt(priv_ep, 0, 0);
 
+	request = cdns3_next_request(&priv_ep->pending_req_list);
+	if (request) {
+		priv_req = to_cdns3_request(request);
+		trb = priv_req->trb;
+		if (trb)
+			trb->control = trb->control ^ TRB_CYCLE;
+	}
+
 	writel(EP_CMD_CSTALL | EP_CMD_EPRST, &priv_dev->regs->ep_cmd);
 
 	/* wait for EPRST cleared */
@@ -2167,10 +2177,11 @@ int __cdns3_gadget_ep_clear_halt(struct
 
 	priv_ep->flags &= ~(EP_STALLED | EP_STALL_PENDING);
 
-	request = cdns3_next_request(&priv_ep->pending_req_list);
-
-	if (request)
+	if (request) {
+		if (trb)
+			trb->control = trb->control ^ TRB_CYCLE;
 		cdns3_rearm_transfer(priv_ep, 1);
+	}
 
 	cdns3_start_all_request(priv_dev, priv_ep);
 	return ret;