The ARM Mali T-series and G-series of GPUs do support compute (OpenCL), the drivers are a different story.
Let's just start out by saying that the GPU designer, ARM, does not support the Open Source driver. Most likely due to their IP-licensing scheme relying on charging customers for the hardware IP and then again charging them for the drivers that they are going to need. Previously the rumors went that they charged customers a 3rd time if they wanted OpenCL support.
This is part of the reason why OpenCL on mobile is dead.
As for actual OpenCL support for Mali GPUs using the Open Source stack, work is progressing, but we (the Mesa & Clover) project aren't there yet.
Regarding the RPi, I don't think it has ever had OpenCL support. Proprietary or otherwise.
About the RPi, Broadcom (the SOC designer) recently lost their very talented GPU driver engineer, due to not being serious enough about pushing the Open Source driver forward.
To answer your question about OpenCL on the RPi in practical terms, it's not possible to use the GPU. But you can use POCL for CPU-backed OpenCL support.
Thanks for the detailed comment! Regarding OpenCL on RPi, what about something like this: https://hackaday.com/2019/01/24/running-opencl-on-a-raspberr...
Do you think it could support ML training/inference on a Pi GPU (albeit very slowly obviously), or even OpenCV?
Let's just start out by saying that the GPU designer, ARM, does not support the Open Source driver. Most likely due to their IP-licensing scheme relying on charging customers for the hardware IP and then again charging them for the drivers that they are going to need. Previously the rumors went that they charged customers a 3rd time if they wanted OpenCL support. This is part of the reason why OpenCL on mobile is dead.
As for actual OpenCL support for Mali GPUs using the Open Source stack, work is progressing, but we (the Mesa & Clover) project aren't there yet.
Regarding the RPi, I don't think it has ever had OpenCL support. Proprietary or otherwise. About the RPi, Broadcom (the SOC designer) recently lost their very talented GPU driver engineer, due to not being serious enough about pushing the Open Source driver forward.
To answer your question about OpenCL on the RPi in practical terms, it's not possible to use the GPU. But you can use POCL for CPU-backed OpenCL support.