On Tue, Feb 13, 2018 at 8:34 AM, Qiang Yu <yuq825@xxxxxxxxx> wrote: > Hi guys, > > I'm working on the Lima project for ARM mali400/450 GPU. Now lima > kernel driver uses CMA for all buffers, but mali400/450 GPU has MMU > for each vertex/fragment shader processor, so I want to refine the lima > kernel driver for non-contiguous memory support. > > After some investigation on current available MM method used by > several linux kernel DRM driver, I can't find an exactly match one for > lima. So I'd like to hear some advise from you and see if I have some > miss understanding on current MMs and if there's better approach. > If can't use existing MM, I may have to write one for lima. > > About Mali400/450 GPU: > 1. it has separate vertex and fragment shader processors, 1 vertex > processor and 1~4 fragment processors are grouped to process an > OpenGL draw > 2. each processor has an MMU work independently > 3. Mali400/450 will work with different display DRM driver, some > display DRM driver support non-contiguous framebuffer and some > not > > My requirement: > 1. support non-contiguous memory allocation as GPU buffer > 2. support contiguous memory allocation too for exporting to some > display DRM driver as framebuffer btw, I think etnaviv deals w/ contiguous scanout buffer by just importing the scanout buffer from the other display drm driver. So I think you could avoid having to allocate these buffers. (iirc, etnaviv does need contiguous buffers internally for a few things, like cmdstream (?) and mmu pagetables) BR, -R > 3. no GPU page fault for better performance and avoid multi MMU > page fault handling, CPU page fault is OK > 4. better have buffer swap to disk feature when memory is full > > Current MM: > 1. drm_gem_cma_object, only support contiguous memory > 2. drm_gem_get_pages > 1) need to combine with cma method for contiguous memory > 2) when shrink is needed, swap some idle buffer to disk and put > pages, need implement by myself > 3) additional shmem layer introduced > 3. TTM TTM_PL_SYSTEM only > 1) no contiguous memory support > 2) too complicated as we don't need other functions of TTM > 3) need GPU page fault to populate memory? > 4) no page pool for cached memory > > My plan: > 1. for contiguous memory allocation use dma_alloc_* > 2. for non-contiguous memory allocation, use a page pool from > alloc_page > 3. buffer is not really allocated when GEM_CREATE, but in CPU > page fault handler and task submit buffer validation which make > sure no GPU page fault > 4. in shrinker handler, free un-used page in the pool, if still not > enough, swap some idle buffer to disk > > 3&4 apply to both dma_alloc buffer and alloc_page buffer. > > Thanks, > Qiang > > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
