dev: Remove the return type from DmaPort::dmaAction.

This function had a comment claiming that returning an arbitrary request
from the call was necessary for page table walker statistics, but
looking at the actual code, the return type was never used. Also
returning whatever the last request happens to be seems arbitrary, and a
bad boundary for modularization. The page table walker should not depend
on the internal implementation of the DMA port.

Change-Id: I00281fbaf6aeb85b15baf54f3d4a23ca1ac72b8b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38716
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/dma_device.cc

@@ -141,7 +141,7 @@ DmaPort::recvReqRetry()
     trySendTimingReq();
 }
 
-RequestPtr
+void
 DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
                    uint8_t *data, uint32_t sid, uint32_t ssid, Tick delay,
                    Request::Flags flag)
@@ -151,10 +151,6 @@ DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
     // i.e. cache line size
     DmaReqState *reqState = new DmaReqState(event, size, delay);
 
-    // (functionality added for Table Walker statistics)
-    // We're only interested in this when there will only be one request.
-    // For simplicity, we return the last request, which would also be
-    // the only request in that case.
     RequestPtr req = nullptr;
 
     DPRINTF(DMA, "Starting DMA for addr: %#x size: %d sched: %d\n", addr, size,
@@ -186,16 +182,14 @@ DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
     // just created, for atomic this involves actually completing all
     // the requests
     sendDma();
-
-    return req;
 }
 
-RequestPtr
+void
 DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
                    uint8_t *data, Tick delay, Request::Flags flag)
 {
-    return dmaAction(cmd, addr, size, event, data,
-                     defaultSid, defaultSSid, delay, flag);
+    dmaAction(cmd, addr, size, event, data,
+              defaultSid, defaultSSid, delay, flag);
 }
 
 void

src/dev/dma_device.hh

@@ -150,11 +150,11 @@ class DmaPort : public RequestPort, public Drainable
 
     DmaPort(ClockedObject *dev, System *s, uint32_t sid=0, uint32_t ssid=0);
 
-    RequestPtr
+    void
     dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
               uint8_t *data, Tick delay, Request::Flags flag=0);
 
-    RequestPtr
+    void
     dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
               uint8_t *data, uint32_t sid, uint32_t ssid, Tick delay,
               Request::Flags flag=0);