dev: Add support for single-pass scan out in the PixelPump

Add a helper function to scan out an entire frame in one time
step. This requires the public PixelPump to be changed somewhat to
separate timing updates from general PixelPump control. Instead of
calling PixelPump::start(timings), timings now need to be updated
using a separate call to PixelPump::updateTimings(timings) before
calling PixelPump::start().

Display controllers that don't need accurate timing (e.g., in KVM
mode), can use the new PixelPump::renderFrame() API to render an
entire frame in one step. This call results in the same callbacks
(e.g., calls to nextPixel()) as the timing calls, but they all happen
in immediately. Unlike the timing counterpart, renderFrame() doesn't
support buffer underruns and will panic if nextPixle() indicates an
underrun.

Change-Id: I76c84db04249b02d4207c5281d82aa693d0881be
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2241
Reviewed-by: Rahul Thakur <rjthakur@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

1 files changed, 58 insertions, 3 deletions

diff --git a/src/dev/pixelpump.cc b/src/dev/pixelpump.cc
index 3ffe96d96..e1cf73af6 100644
--- a/src/dev/pixelpump.cc
+++ b/src/dev/pixelpump.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015 ARM Limited
+ * Copyright (c) 2015, 2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -136,10 +136,11 @@ BasePixelPump::unserialize(CheckpointIn &cp)
         event->unserializeSection(cp, event->name());
 }
 
-
 void
-BasePixelPump::start(const DisplayTimings &timings)
+BasePixelPump::updateTimings(const DisplayTimings &timings)
 {
+    panic_if(active(), "Trying to update timings in active PixelPump\n");
+
     _timings = timings;
 
     // Resize the frame buffer if needed
@@ -149,9 +150,15 @@ BasePixelPump::start(const DisplayTimings &timings)
     // Set the current line past the last line in the frame. This
     // triggers the new frame logic in beginLine().
     line = _timings.linesPerFrame();
+}
+
+void
+BasePixelPump::start()
+{
     schedule(evBeginLine, clockEdge());
 }
 
+
 void
 BasePixelPump::stop()
 {
@@ -241,6 +248,54 @@ BasePixelPump::renderPixels()
     }
 }
 
+void
+BasePixelPump::renderFrame()
+{
+    _underrun = false;
+    line = 0;
+
+    // Signal vsync end and render the frame
+    line = _timings.lineVBackPorchStart();
+    onVSyncEnd();
+
+    // We only care about the visible screen area when rendering the
+    // frame
+    for (line = _timings.lineFirstVisible();
+        line < _timings.lineFrontPorchStart();
+        ++line) {
+
+        _posX = 0;
+
+        onHSyncBegin();
+        onHSyncEnd();
+
+        renderLine();
+    }
+
+    line = _timings.lineFrontPorchStart() - 1;
+    onFrameDone();
+
+    // Signal vsync until the next frame begins
+    line = _timings.lineVSyncStart();
+    onVSyncBegin();
+}
+
+void
+BasePixelPump::renderLine()
+{
+    const unsigned pos_y(posY());
+
+    Pixel pixel(0, 0, 0);
+    for (_posX = 0; _posX < _timings.width; ++_posX) {
+        if (!nextPixel(pixel)) {
+            panic("Unexpected underrun in BasePixelPump (%u, %u)\n",
+                 _posX, pos_y);
+        }
+        fb.pixel(_posX, pos_y) = pixel;
+    }
+}
+
+
 BasePixelPump::PixelEvent::PixelEvent(
     const char *name, BasePixelPump *_parent, CallbackType _func)
     : Event(), Drainable(),