[PATCH] usb: dwc3: gadget: delay unmap of bounced requests

[Felipe Balbi]

From: Janusz Dziedzic <januszx.dzied...@intel.com>

In the case of bounced ep0 requests, we must delay DMA operation until
after ->complete() otherwise we might overwrite contents of req->buf.

This caused problems with RNDIS gadget.

Signed-off-by: Janusz Dziedzic <januszx.dzied...@intel.com>
Signed-off-by: Felipe Balbi <felipe.ba...@linux.intel.com>
---
 drivers/usb/dwc3/gadget.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 0d75158e43fe..79e7a3480d51 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -171,6 +171,7 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct 
dwc3_request *req,
                int status)
 {
        struct dwc3                     *dwc = dep->dwc;
+       unsigned int                    unmap_after_complete = false;
 
        req->started = false;
        list_del(&req->list);
@@ -180,11 +181,19 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct 
dwc3_request *req,
        if (req->request.status == -EINPROGRESS)
                req->request.status = status;
 
-       if (dwc->ep0_bounced && dep->number <= 1)
+       /*
+        * NOTICE we don't want to unmap before calling ->complete() if we're
+        * dealing with a bounced ep0 request. If we unmap it here, we would end
+        * up overwritting the contents of req->buf and this could confuse the
+        * gadget driver.
+        */
+       if (dwc->ep0_bounced && dep->number <= 1) {
                dwc->ep0_bounced = false;
-
-       usb_gadget_unmap_request_by_dev(dwc->sysdev,
-                       &req->request, req->direction);
+               unmap_after_complete = true;
+       } else {
+               usb_gadget_unmap_request_by_dev(dwc->sysdev,
+                               &req->request, req->direction);
+       }
 
        trace_dwc3_gadget_giveback(req);
 
@@ -192,6 +201,10 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct 
dwc3_request *req,
        usb_gadget_giveback_request(&dep->endpoint, &req->request);
        spin_lock(&dwc->lock);
 
+       if (unmap_after_complete)
+               usb_gadget_unmap_request_by_dev(dwc->sysdev,
+                               &req->request, req->direction);
+
        if (dep->number > 1)
                pm_runtime_put(dwc->dev);
 }
-- 
2.11.0.295.gd7dffce1ce

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