The i.MX6 Q/D has a 3D GPU, a 2D GPU and a Vector Graphic Unit.
The i.MX 6DL/S has 3D GPU with less performance, the same 2D GPU and no Vector Graphic Unit.
The Vector Graphic Unit is used to provide OpenVG, on the i.MX 6DL/S the OpenVG driver emulates the Vector Graphic Unit by using the 3D GPU.
The fact that the i.MX 6DL/S driver has no clock by the name “openvg_axi_clk” makes the driver not configuring that not existing hardware and it outputs the informational message “galcore: clk_get vg clock failed, disable vg!”.
Since the clock tree is different between dual light and quad in some places but the clock code is common for both i.MX 6 flavours that leads to some strange sounding clock names.
Note that that code is part of the NXP downstream kernel, so comparing it with the different GPU implementation in mainline does not really help. There is also nothing new with this clock definitions in the 4.1 kernel used for 2.7b3, it has been like this starting with the 3.10.17 kernel and it is still present in the 4.9 kernel which NXP has just released (and we did not yet port to our modules).
