LdB wrote: ↑
Sun May 02, 2021 9:59 am
Usually same deal in user-space FPU mode would typically be disabled (unless Raspbian is unusal).. you would need to install a device driver.
Indeed i must do a lot of reading...
I found the solution... and its not a kernel or Raspbian problem.
I will try to summarize:
1- VFPU is enable by default in raspbian and users can access without problem (default mode is scalar, which means no SIMD - single instruction multiple data).
2- PI's like 2, 3 and 4 ARM CPU use NEON for vfp (vector floating point which allows SIMD), yet they still have the VFPU (v3/v4 compatibility reasons i guess?) but only for scalar mode (yeah i should check the cpu's datasheet to confirm this)
3-PI's like 1 and zero ARM CPU doesn't have NEON and since both use an ARM1176JZF-S which has a VPFU v2, it has to support vfp... and guess what? it does i just tried the code in my pi zero and it works.
Conclusion for vfp:
-Pi 0/1 set len and stride in fpscr.
-Pi 2/3/4 use neon instructions.
So it goes to trash my idea of writing vfp code (SIMD) for pi 0 and use it in both my pi 0 and 3.