From: Gabe Black <gabe.black@gmail.com>
Date: Thu, 24 Dec 2020 14:48:21 +0000 (-0800)
Subject: dev: Use regular atomic accesses for DMA in bypass mode.
X-Git-Tag: develop-gem5-snapshot~310
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=43114ad1dd678595a5a67c761f56508d3df3b4b7;p=gem5.git

dev: Use regular atomic accesses for DMA in bypass mode.

These are now accelerated with backdoor accesses and should be at least
as fast as functional accesses. This removes a dependency on port
proxies, and also stops the HDLCD from using functional accesses.

Change-Id: I5e959288eb533d09cffa7b79938aa2f61e4aff7d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38720
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---

diff --git a/src/dev/dma_device.cc b/src/dev/dma_device.cc
index bbdae7df0..9aebb7bd3 100644
--- a/src/dev/dma_device.cc
+++ b/src/dev/dma_device.cc
@@ -370,8 +370,8 @@ DmaReadFifo::DmaReadFifo(DmaPort &_port, size_t size,
                          unsigned max_pending,
                          Request::Flags flags)
     : maxReqSize(max_req_size), fifoSize(size),
-      reqFlags(flags), port(_port), proxy(port, port.sys->cacheLineSize()),
-      cacheLineSize(port.sys->cacheLineSize()), buffer(size)
+      reqFlags(flags), port(_port), cacheLineSize(port.sys->cacheLineSize()),
+      buffer(size)
 {
     freeRequests.resize(max_pending);
     for (auto &e : freeRequests)
@@ -465,7 +465,7 @@ DmaReadFifo::resumeFill()
     const bool old_eob(atEndOfBlock());
 
     if (port.sys->bypassCaches())
-        resumeFillFunctional();
+        resumeFillBypass();
     else
         resumeFillTiming();
 
@@ -474,7 +474,7 @@ DmaReadFifo::resumeFill()
 }
 
 void
-DmaReadFifo::resumeFillFunctional()
+DmaReadFifo::resumeFillBypass()
 {
     const size_t fifo_space = buffer.capacity() - buffer.size();
     if (fifo_space >= cacheLineSize || buffer.capacity() < cacheLineSize) {
@@ -483,11 +483,13 @@ DmaReadFifo::resumeFillFunctional()
         std::vector<uint8_t> tmp_buffer(xfer_size);
 
         assert(pendingRequests.empty());
-        DPRINTF(DMA, "KVM Bypassing startAddr=%#x xfer_size=%#x " \
+        DPRINTF(DMA, "Direct bypass startAddr=%#x xfer_size=%#x " \
                 "fifo_space=%#x block_remaining=%#x\n",
                 nextAddr, xfer_size, fifo_space, block_remaining);
 
-        proxy.readBlob(nextAddr, tmp_buffer.data(), xfer_size);
+        port.dmaAction(MemCmd::ReadReq, nextAddr, xfer_size, nullptr,
+                tmp_buffer.data(), 0, reqFlags);
+
         buffer.write(tmp_buffer.begin(), xfer_size);
         nextAddr += xfer_size;
     }
diff --git a/src/dev/dma_device.hh b/src/dev/dma_device.hh
index 3904a082d..330be1ac2 100644
--- a/src/dev/dma_device.hh
+++ b/src/dev/dma_device.hh
@@ -49,7 +49,6 @@
 #include "base/circlebuf.hh"
 #include "dev/io_device.hh"
 #include "mem/backdoor.hh"
-#include "mem/port_proxy.hh"
 #include "params/DmaDevice.hh"
 #include "sim/drain.hh"
 #include "sim/system.hh"
@@ -508,7 +507,6 @@ class DmaReadFifo : public Drainable, public Serializable
     const Request::Flags reqFlags;
 
     DmaPort &port;
-    PortProxy proxy;
 
     const int cacheLineSize;
 
@@ -554,8 +552,8 @@ class DmaReadFifo : public Drainable, public Serializable
     /** Try to issue new DMA requests during normal execution*/
     void resumeFillTiming();
 
-    /** Try to bypass DMA requests in KVM execution mode */
-    void resumeFillFunctional();
+    /** Try to bypass DMA requests in non-caching mode */
+    void resumeFillBypass();
 
   private: // Internal state
     Fifo<uint8_t> buffer;