Freedreno DRM/Gallium3D Shines Well For ARM
The reverse-engineered Freedreno driver for open-source Qualcomm Adreno graphics support is quickly taking shape as the leading ARM Linux graphics driver for the (non-Android) Linux desktop.
Rob Clark of Red Hat (formerly with Texas Instruments) has been working on Freedreno the past year and he's made a ton of progress for doing most things single-handedly and as a hobbyist project. His Freedreno Gallium3D driver is the first mainline ARM Mesa/Gallium3D driver and that's running well and in good shape for Mesa 9.2.
Earlier this month he then published a Qualcomm KMS/DRM driver rather than having to rely upon Qualcomm's low-quality open-source kernel driver primarily designed around Android's needs. He also has his xf86-video-freedreno driver for providing the X.Org driver support and 2D acceleration is being leveraged over the XA state tracker in Gallium3D.
For explaining where things are today, Rob wrote a new blog post concerning Freedreno Gallium3D and the new DRM/KMS driver.
While Qualcomm's kernel driver for Adreno display/graphics is open-source, the code quality is terrible, according to Rob. He says he ended up writing his own code to trace all the register read/writes to the hardware rather than simply porting the code to the DRM/KMS interfaces. (Qualcomm continues to refrain from publicly disclosing any hardware specifications / programming guides and they do not support the Freedreno project.)
Rob said, "Unfortunately, the msm android fbdev driver code is a real mess (at least the mdp4 parts). Even by android / vendor kernel standards, which are pretty low to begin with. And I don't have any docs on the display controller. In the end, I ended up instrumenting the code to trace all the register reads/writes, etc, wrote a small parser tool using envytools/librnn, and starting writing rnndb register database for the display controller registers. It was a lot easier to get a general picture of how the hardware works that way! Plus I can generate register level headers from rnndb in the same way I do for the gallium driver."
He also says in today's blog post that he expects his next revision of the MSM DRM/KMS driver to be in good shape and hopefully the final "RFC" round, which would mean this new driver could potentially premiere in the Linux 3.12 kernel.
Embedded below is the Freedreno driver stack (with the new kernel driver) running on the IFC6410 ARM development board with quad-core Krait SoC and Adreno A320 graphics.
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