Qiang Yu <yuq...@gmail.com> writes: > - Mali 4xx GPUs have two kinds of processors GP and PP. GP is for > OpenGL vertex shader processing and PP is for fragment shader > processing. Each processor has its own MMU so prcessors work in > virtual address space. > - There's only one GP but multiple PP (max 4 for mali 400 and 8 > for mali 450) in the same mali 4xx GPU. All PPs are grouped > togather to handle a single fragment shader task divided by > FB output tiled pixels. Mali 400 user space driver is > responsible for assign target tiled pixels to each PP, but mali > 450 has a HW module called DLBU to dynamically balance each > PP's load. > - User space driver allocate buffer object and map into GPU > virtual address space, upload command stream and draw data with > CPU mmap of the buffer object, then submit task to GP/PP with > a register frame indicating where is the command stream and misc > settings. > - There's no command stream validation/relocation due to each user > process has its own GPU virtual address space. GP/PP's MMU switch > virtual address space before running two tasks from different > user process. Error or evil user space code just get MMU fault > or GP/PP error IRQ, then the HW/SW will be recovered. > - Use GEM+shmem for MM. Currently just alloc and pin memory when > gem object creation. GPU vm map of the buffer is also done in > the alloc stage in kernel space. We may delay the memory > allocation and real GPU vm map to command submission stage in the > furture as improvement. > - Use drm_sched for GPU task schedule. Each OpenGL context should > have a lima context object in the kernel to distinguish tasks > from different user. drm_sched gets task from each lima context > in a fair way. > > mesa driver can be found here before upstreamed: > https://gitlab.freedesktop.org/lima/mesa > > v7: > - remove lima_fence_ops with default value > - move fence slab create to device probe > - check pad ioctl args to be zero > - add comments for user/kernel interface
Thanks for adding the comments! That helps a lot. I feel pretty good about the ABI at this point. Reviewed-by: Eric Anholt <e...@anholt.net>
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