From 22f5665de79513c41fbef8f1b918f44d184daf1f Mon Sep 17 00:00:00 2001
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From: Jeffy Chen <jeffy.chen@rock-chips.com>
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Date: Tue, 16 Apr 2019 18:46:49 +0800
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Subject: [PATCH 17/31] linuxfb: Use triple buffer by default
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Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
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---
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.../platforms/linuxfb/qlinuxfbdrmscreen.cpp | 56 +++++++++++++++----
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1 file changed, 44 insertions(+), 12 deletions(-)
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diff --git a/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp b/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
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index dcc1ef27..29d146f4 100644
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--- a/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
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+++ b/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
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@@ -59,7 +59,13 @@ QT_BEGIN_NAMESPACE
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Q_LOGGING_CATEGORY(qLcFbDrm, "qt.qpa.fb")
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+#define TRIPLE_BUFFER
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+
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+#ifdef TRIPLE_BUFFER
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+static const int BUFFER_COUNT = 3;
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+#else
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static const int BUFFER_COUNT = 2;
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+#endif
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class QLinuxFbDevice : public QKmsDevice
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{
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@@ -75,12 +81,12 @@ public:
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};
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struct Output {
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- Output() : backFb(0), flipped(false) { }
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+ Output() : backFb(0), flipPending(false) { }
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QKmsOutput kmsOutput;
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Framebuffer fb[BUFFER_COUNT];
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QRegion dirty[BUFFER_COUNT];
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int backFb;
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- bool flipped;
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+ bool flipPending;
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QSize currentRes() const {
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const drmModeModeInfo &modeInfo(kmsOutput.modes[kmsOutput.mode]);
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return QSize(modeInfo.hdisplay, modeInfo.vdisplay);
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@@ -97,6 +103,7 @@ public:
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void setMode();
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void swapBuffers(Output *output);
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+ void waitForFlip(Output *output);
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int outputCount() const { return m_outputs.count(); }
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Output *output(int idx) { return &m_outputs[idx]; }
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@@ -301,7 +308,7 @@ void QLinuxFbDevice::createFramebuffers()
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return;
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}
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output.backFb = 0;
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- output.flipped = false;
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+ output.flipPending = false;
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}
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}
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@@ -355,19 +362,18 @@ void QLinuxFbDevice::pageFlipHandler(int fd, unsigned int sequence,
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Q_UNUSED(tv_usec);
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Output *output = static_cast<Output *>(user_data);
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+
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+#ifndef TRIPLE_BUFFER
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+ // The next buffer would be available after flipped
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output->backFb = (output->backFb + 1) % BUFFER_COUNT;
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+#endif
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+
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+ output->flipPending = false;
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}
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-void QLinuxFbDevice::swapBuffers(Output *output)
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+void QLinuxFbDevice::waitForFlip(Output *output)
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{
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- Framebuffer &fb(output->fb[output->backFb]);
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- if (drmModePageFlip(fd(), output->kmsOutput.crtc_id, fb.fb, DRM_MODE_PAGE_FLIP_EVENT, output) == -1) {
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- qErrnoWarning(errno, "Page flip failed");
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- return;
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- }
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-
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- const int fbIdx = output->backFb;
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- while (output->backFb == fbIdx) {
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+ while (output->flipPending) {
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drmEventContext drmEvent;
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memset(&drmEvent, 0, sizeof(drmEvent));
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drmEvent.version = 2;
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@@ -379,6 +385,27 @@ void QLinuxFbDevice::swapBuffers(Output *output)
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}
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}
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+void QLinuxFbDevice::swapBuffers(Output *output)
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+{
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+#ifdef TRIPLE_BUFFER
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+ // Wait flip to make sure last buffer displayed
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+ waitForFlip(output);
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+#endif
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+
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+ Framebuffer &fb(output->fb[output->backFb]);
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+ if (drmModePageFlip(fd(), output->kmsOutput.crtc_id, fb.fb, DRM_MODE_PAGE_FLIP_EVENT, output) == -1) {
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+ qErrnoWarning(errno, "Page flip failed");
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+ return;
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+ }
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+
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+ output->flipPending = true;
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+
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+#ifdef TRIPLE_BUFFER
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+ // The next buffer should always available in triple buffer case.
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+ output->backFb = (output->backFb + 1) % BUFFER_COUNT;
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+#endif
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+}
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+
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QLinuxFbDrmScreen::QLinuxFbDrmScreen(const QStringList &args)
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: m_screenConfig(nullptr),
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m_device(nullptr)
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@@ -436,6 +463,11 @@ QRegion QLinuxFbDrmScreen::doRedraw()
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for (int i = 0; i < BUFFER_COUNT; ++i)
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output->dirty[i] += dirty;
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+#ifndef TRIPLE_BUFFER
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+ // Wait flip before accessing new buffer
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+ m_device->waitForFlip(output);
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+#endif
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+
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if (output->fb[output->backFb].wrapper.isNull())
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return dirty;
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--
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2.20.1
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