eglfs/kms: Add framebuffer scaling ability with KMS atomic

This commit will add the possibility to have a different sizes between
framebuffer and videomode using DRM atomic, which is not possible with
DRM legacy.

The main goal of this change is to allow to get decent performance on
embedded devices which can support high resolution display (ie UHD),
and which don't have a GPU able to achieve decent framerate in such
resolutions.

This patch adds a "size" member to the output configuration in KMS
configuration file. The GBM framebuffer will be created with that
size and the GBM screen will report that size so that EGLFS can do
everything normally.

Scaling planes with different size than the video mode size is not
something supported consistently with DRM legacy, so that feature
will be only available when using the DRM atomic API.

This was tested on Rock64 device, both with drm legacy and atomic.

Change-Id: I8ba5bae35e61fcb7d9fc58234504bdfd647b43f6
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Lionel CHAZALLON <longchair@hotmail.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/platformsupport/kmsconvenience/qkmsdevice.cpp b/src/platformsupport/kmsconvenience/qkmsdevice.cpp
index 99297c8a3c..c383f51472 100644
--- a/src/platformsupport/kmsconvenience/qkmsdevice.cpp
+++ b/src/platformsupport/kmsconvenience/qkmsdevice.cpp
@@ -366,6 +366,25 @@ QPlatformScreen *QKmsDevice::createScreenForConnector(drmModeResPtr resources,
     if (!cloneSource.isEmpty())
         qCDebug(qLcKmsDebug) << "Output" << connectorName << " clones output " << cloneSource;
 
+    const QByteArray fbsize = userConnectorConfig.value(QStringLiteral("size")).toByteArray().toLower();
+    QSize framebufferSize;
+    framebufferSize.setWidth(modes[selected_mode].hdisplay);
+    framebufferSize.setHeight(modes[selected_mode].vdisplay);
+
+#if QT_CONFIG(drm_atomic)
+    if (hasAtomicSupport()) {
+        if (sscanf(fbsize.constData(), "%dx%d", &framebufferSize.rwidth(), &framebufferSize.rheight()) != 2) {
+            qWarning("Framebuffer size format is invalid.");
+        }
+    } else {
+        qWarning("Setting framebuffer size is only available with DRM atomic API");
+    }
+#else
+    if (fbsize.size())
+        qWarning("Setting framebuffer size is only available with DRM atomic API");
+#endif
+    qCDebug(qLcKmsDebug) << "Output" << connectorName << "framebuffer size is " << framebufferSize;
+
     QKmsOutput output;
     output.name = QString::fromUtf8(connectorName);
     output.connector_id = connector->connector_id;
@@ -385,6 +404,7 @@ QPlatformScreen *QKmsDevice::createScreenForConnector(drmModeResPtr resources,
     output.forced_plane_set = false;
     output.drm_format = drmFormat;
     output.clone_source = cloneSource;
+    output.size = framebufferSize;
 
 #if QT_CONFIG(drm_atomic)
     if (drmModeCreatePropertyBlob(m_dri_fd, &modes[selected_mode], sizeof(drmModeModeInfo),
@@ -788,6 +808,14 @@ void QKmsDevice::discoverPlanes()
                 plane.crtcPropertyId = prop->prop_id;
             } else if (!strcasecmp(prop->name, "fb_id")) {
                 plane.framebufferPropertyId = prop->prop_id;
+            } else if (!strcasecmp(prop->name, "src_w")) {
+                plane.srcwidthPropertyId = prop->prop_id;
+            } else if (!strcasecmp(prop->name, "src_h")) {
+                plane.srcheightPropertyId = prop->prop_id;
+            } else if (!strcasecmp(prop->name, "crtc_w")) {
+                plane.crtcwidthPropertyId = prop->prop_id;
+            } else if (!strcasecmp(prop->name, "crtc_h")) {
+                plane.crtcheightPropertyId = prop->prop_id;
             }
         });