Way back in January this patchset: http://lists.freedesktop.org/archives/dri-devel/2011-January/006905.html was merged in, but pieces of it had to be reverted b/c they did not work properly under PowerPC, ARM, and when swapping out pages to disk.
After a bit of discussion on the mailing list http://marc.info/?i=4D769726.2030307@shipmail.org I started working on it, but got waylaid by other things .. and finally I am able to post the RFC patches.
There was a lot of discussion about it and I am not sure if I captured everybody's thoughts - if I did not - that is _not_ intentional - it has just been quite some time..
Anyhow .. the patches explore what the "lib/dmapool.c" does - which is to have a DMA pool that the device has associated with. I kind of married that code along with drivers/gpu/drm/ttm/ttm_page_alloc.c to create a TTM DMA pool code. The end result is DMA pool with extra features: can do write-combine, uncached, writeback (and tracks them and sets back to WB when freed); tracks "cached" pages that don't really need to be returned to a pool; and hooks up to the shrinker code so that the pools can be shrunk.
If you guys think this set of patches make sense - my future plans were to move a bulk of this in the lib/dmapool.c (I spoke with Matthew Wilcox about it and he is OK as long as I don't introduce performance regressions).
As I mentioned, in the past, the patches I introduced broke certain scenarios so I've been running compile/runtime tests to make sure I don't repeat my past mistakes. Both nouveau and radeon - IGP, PCI-e, and with various IOMMUs - Calgary, GART, SWIOTLB, Xen SWIOTLB, AMD-VI work correctly (still need to test Intel VT-d).
My PowerPC has issues with booting a virgin 3.0 kernel (something about "ELF image not correct") so I don't have that yet covered.
The patches are also located in a git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git devel/ttm.dma_pool.v1.5
And the full diffstat is:
drivers/gpu/drm/nouveau/nouveau_mem.c | 3 +- drivers/gpu/drm/nouveau/nouveau_sgdma.c | 3 +- drivers/gpu/drm/radeon/radeon_gart.c | 4 +- drivers/gpu/drm/radeon/radeon_ttm.c | 3 +- drivers/gpu/drm/ttm/Makefile | 3 + drivers/gpu/drm/ttm/ttm_bo.c | 4 +- drivers/gpu/drm/ttm/ttm_memory.c | 5 + drivers/gpu/drm/ttm/ttm_page_alloc.c | 63 ++- drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 1311 ++++++++++++++++++++++++++++++ drivers/gpu/drm/ttm/ttm_tt.c | 5 +- drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 4 +- drivers/xen/swiotlb-xen.c | 2 +- include/drm/ttm/ttm_bo_driver.h | 7 +- include/drm/ttm/ttm_page_alloc.h | 100 +++- include/linux/swiotlb.h | 7 +- lib/swiotlb.c | 5 +- 16 files changed, 1499 insertions(+), 30 deletions(-)