[Mesa-dev] Broadcom VideoCore IV

[Rob Clark]

On Sat, Apr 19, 2014 at 9:32 AM, Mohamed MEDIOUNI
<mohamedmediouni91 at gmail.com> wrote:
> The VideoCore IV GPU has 14 cores:
>
> - 2 VPU Cores : Full-blown cores which run the ThreadX RTOS.
> There is an experimental LLVM port to it and also the VBCC C89
> compiler(which has'nt time support so classic benchmarks run indefinitely).
> The binary blob run on that.
> 5 GFlops
>
> - 12 QPU Cores : 3D cores officially documented by Broadcom and using a
> tile-mode rendering architecture.
> The full Android driver for that was open-sourced at the end of February.
>
> 24Gflops
>
> Questions:
>
> Can Gallium3D run with tile-mode rendering architecture ?

yes, adreno (freedreno) is a tiler

> Is it better using Mesa and  the Broadcom shader compiler ?

Allegedly it may be easier to shoehorn in the blob compiler with a
mesa/dri driver vs mesa/gallium driver.  That probably shouldn't be
too much of a concern in the long run.  Overall I think a gallium
driver would be much easier to implement... gallium plus helpers
provide a lot to the driver writer.

> Is it better using the VPU and an adapted LLVMpipe ?

I guess you are talking about keeping the driver-on-videocore
approach?  That may have some advantages when it comes to handling
security (lack of mmu) on r-pi.  But other than that, I suspect
everything else will be easier to develop/debug on the arm side.  And
I suspect avoiding round trips to the coprocessor will help
performance in a lot of cases.

so if you can figure out a way to deal with security aspect with arm
side driver, then I'd go for arm side gallium driver as my first
choice.

BR,
-R

>
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