usb: dwc3: gadget: delay unmap of bounced requests

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.dziedzic@intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

1 files 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);
 }