On Mon, Jan 21, 2019 at 9:46 AM Lubomir Rintel lkundrak@v3.sk wrote:
On Mon, 2019-01-21 at 09:35 -0600, Rob Herring wrote:
On Sun, Jan 20, 2019 at 11:26 AM Lubomir Rintel lkundrak@v3.sk wrote:
The Marvell Armada DRM master device is a virtual device needed to list all nodes that comprise the graphics subsystem.
Signed-off-by: Lubomir Rintel lkundrak@v3.sk
.../display/armada/marvell-armada-drm.txt | 24 +++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/Documentation/devicetree/bindings/display/armada/marvell-armada-drm.txt b/Documentation/devicetree/bindings/display/armada/marvell-armada-drm.txt index de4cca9432c8..3dbfa8047f0b 100644 --- a/Documentation/devicetree/bindings/display/armada/marvell-armada-drm.txt +++ b/Documentation/devicetree/bindings/display/armada/marvell-armada-drm.txt @@ -1,3 +1,27 @@ +Marvell Armada DRM master device +================================
+The Marvell Armada DRM master device is a virtual device needed to list all +nodes that comprise the graphics subsystem.
+Required properties:
- compatible: value should be "marvell,dove-display-subsystem",
- "marvell,armada-display-subsystem"
- ports: a list of phandles pointing to display interface ports of CRTC
- devices
- memory-region: phandle to a node describing memory to be used for the
- framebuffer
+Example:
display-subsystem {compatible = "marvell,dove-display-subsystem","marvell,armada-display-subsystem";memory-region = <&display_reserved>;ports = <&lcd0_port>;If there is only one device, you don't need this virtual node.
By "one device" you mean one LCD controller (CRTC)?
Yes.
I suppose in the (single CRTC) example case, the display-subsystem node used to associate it with the memory region reserved for allocating the frame buffers from. Could that be done differently?
Move memory-region to the LCD controller node.
Also, if the node is indeed made optional, then it's going to complicate things on the DRM side. Currently the driver that binds to the node creates the DRM device once it sees all the components connected to the ports appear. If we loose it, then the LCD controller driver would somehow need to find out that it's alone and create the DRM device itself.
DT is not the only way to create devices. The DRM driver can bind to the LCDC node and then create a child CRTC device (or even multiple ones for h/w with multiple pipelines).
You'll also notice that there are only 3 cases of this virtual node in the tree: STi, i.MX IPU, and Rockchip. That's because we've deprecated doing these virtual nodes for some time now. IOW, there are several examples of how to do this without a virtual node.
Rob