[gem5-dev] Change in gem5/gem5[develop]: dev: Use regular atomic accesses for DMA in bypass mode.

[Gabe Black (Gerrit) via gem5-dev]

Gabe Black has submitted this change. (  
https://gem5-review.googlesource.com/c/public/gem5/+/38720 )

Change subject: dev: Use regular atomic accesses for DMA in bypass mode.
......................................................................
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.sandb...@arm.com>
Maintainer: Andreas Sandberg <andreas.sandb...@arm.com>
Tested-by: kokoro <noreply+kok...@google.com>
---
M src/dev/dma_device.cc
M src/dev/dma_device.hh
2 files changed, 10 insertions(+), 10 deletions(-)

Approvals:
  Andreas Sandberg: Looks good to me, approved; Looks good to me, approved
  kokoro: Regressions pass



diff --git a/src/dev/dma_device.cc b/src/dev/dma_device.cc
index bbdae7d..9aebb7b 100644
--- a/src/dev/dma_device.cc
+++ b/src/dev/dma_device.cc
@@ -370,8 +370,8 @@
                          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 @@
     const bool old_eob(atEndOfBlock());

     if (port.sys->bypassCaches())
-        resumeFillFunctional();
+        resumeFillBypass();
     else
         resumeFillTiming();

@@ -474,7 +474,7 @@
 }

 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 @@
         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 3904a08..330be1a 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 @@
     const Request::Flags reqFlags;

     DmaPort &port;
-    PortProxy proxy;

     const int cacheLineSize;

@@ -554,8 +552,8 @@
     /** 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;

--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I5e959288eb533d09cffa7b79938aa2f61e4aff7d
Gerrit-Change-Number: 38720
Gerrit-PatchSet: 13
Gerrit-Owner: Gabe Black <gabe.bl...@gmail.com>
Gerrit-Reviewer: Andreas Sandberg <andreas.sandb...@arm.com>
Gerrit-Reviewer: Daniel Carvalho <oda...@yahoo.com.br>
Gerrit-Reviewer: Gabe Black <gabe.bl...@gmail.com>
Gerrit-Reviewer: Giacomo Travaglini <giacomo.travagl...@arm.com>
Gerrit-Reviewer: Nikos Nikoleris <nikos.nikole...@arm.com>
Gerrit-Reviewer: kokoro <noreply+kok...@google.com>
Gerrit-MessageType: merged
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