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GPU LED blinking

Posted: Sat Oct 14, 2017 9:40 am
by Gavinmc42
Lots of baremetal is about booting the VC4 and then switching the ARM on and doing stuff on the ARM.

OpenCL on VC4 has got me thinking about the GPU/QPU

Has anyone blinked a GPIO LED with QPU code?
Activity led is initially under VPU control on boot?

Been wondering if the QPU's could be used as real time controllers
Nanokernel's in QPU?
I have not seen QPU specific timers, VPU's have any?

I assume the ThreedX OS is running in one VPU after bootcode.bin is running.
This would leave the other VPU free, unless the ThreadX is running multicores :o

Re: GPU LED blinking

Posted: Sat Oct 14, 2017 10:01 am
by Akane
Dom, who is an engineer at Pi Towers, said QPU cannot access the peripheral bus: viewtopic.php?f=72&t=128309. So it's unlikely I think.

Re: GPU LED blinking

Posted: Sat Oct 14, 2017 10:16 am
by Gavinmc42
Thanks.
Unlikely unless QPU's can access memory directly?

So probably need to stick to just the VPU.
Start with the alternative bootloaders for examples.
Is there a VPU C compiler? google time.
GCC on Videocore :D probably better to use LLVM?
Time to learn something new LLVM :D