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authorLinus Torvalds <torvalds@linux-foundation.org>2021-03-11 17:38:49 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-03-11 17:38:49 -0800
commitf78d76e72a4671ea52d12752d92077788b4f5d50 (patch)
tree766ddd53e87c813fdaa935b11a30638928f8bd5e /Documentation
parent28806e4d9b97865b450d72156e9ad229f2067f0b (diff)
parent4042160c2e5433e0759782c402292a90b5bf458d (diff)
Merge tag 'drm-fixes-2021-03-12-1' of git://anongit.freedesktop.org/drm/drm
Pull drm fixes from Dave Airlie: "Regular fixes for rc3. The i915 pull was based on the rc1 tag so I just cherry-picked the single fix from there to avoid it. The misc and amd trees seem to be on okay bases. It's a bunch of fixes across the tree, amdgpu has most of them a few ttm fixes around qxl, and nouveau. core: - Clear holes when converting compat ioctl's between 32-bits and 64-bits. docs: - Use gitlab for drm bugzilla now. ttm: - Fix ttm page pool accounting. fbdev: - Fix oops in drm_fbdev_cleanup() shmem: - Assorted fixes for shmem helpers. qxl: - unpin qxl bos created as pinned when freeing them, and make ttm only warn once on this behavior. - Zero head.surface_id correctly in qxl. atyfb: - Use LCD management for atyfb on PPC_MAC. meson: - Shutdown kms poll helper in meson correctly. nouveau: - fix regression in bo syncing i915: - Wedge the GPU if command parser setup fails amdgpu: - Fix aux backlight control - Add a backlight override parameter - Various display fixes - PCIe DPM fix for vega - Polaris watermark fixes - Additional S0ix fix radeon: - Fix GEM regression - Fix AGP dependency handling" * tag 'drm-fixes-2021-03-12-1' of git://anongit.freedesktop.org/drm/drm: (33 commits) drm/nouveau: fix dma syncing for loops (v2) drm/i915: Wedge the GPU if command parser setup fails drm/compat: Clear bounce structures drm/shmem-helpers: vunmap: Don't put pages for dma-buf drm: meson_drv add shutdown function drm/shmem-helper: Don't remove the offset in vm_area_struct pgoff drm/shmem-helper: Check for purged buffers in fault handler qxl: Fix uninitialised struct field head.surface_id drm/ttm: Fix TTM page pool accounting drm/ttm: soften TTM warnings drm: Use USB controller's DMA mask when importing dmabufs MAINTAINERS: update drm bug reporting URL fbdev: atyfb: use LCD management functions for PPC_PMAC also fbdev: atyfb: always declare aty_{ld,st}_lcd() drm/qxl: fix lockdep issue in qxl_alloc_release_reserved drm/qxl: unpin release objects drm/fb-helper: only unmap if buffer not null drm/amdgpu: fix S0ix handling when the CONFIG_AMD_PMC=m drm/radeon: fix AGP dependency drm/radeon: also init GEM funcs in radeon_gem_prime_import_sg_table ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/gpu/todo.rst21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 40ccac61137e..22ce801e3a8d 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -613,6 +613,27 @@ Some of these date from the very introduction of KMS in 2008 ...
Level: Intermediate
+Remove automatic page mapping from dma-buf importing
+----------------------------------------------------
+
+When importing dma-bufs, the dma-buf and PRIME frameworks automatically map
+imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and
+drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach()
+even if they never do actual device DMA, but only CPU access through
+dma_buf_vmap(). This is a problem for USB devices, which do not support DMA
+operations.
+
+To fix the issue, automatic page mappings should be removed from the
+buffer-sharing code. Fixing this is a bit more involved, since the import/export
+cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over
+this problem for USB devices by fishing out the USB host controller device, as
+long as that supports DMA. Otherwise importing can still needlessly fail.
+
+Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
+
+Level: Advanced
+
+
Better Testing
==============