Am 22.02.21 um 13:43 schrieb Thomas Zimmermann:
USB-based drivers cannot use DMA, so the importing of dma-buf attachments
currently fails for udl and gm12u320. This breaks joining/mirroring of
displays.
The fix is now a little series. To solve the issue on the importer
side (i.e., the affected USB-based driver), patch 1 introduces a new
PRIME callback, struct drm_driver.gem_prime_create_object, which creates
an object and gives more control to the importing driver. Specifically,
udl and gm12u320 can now avoid the creation of a scatter/gather table
for the imported pages. Patch 1 is self-contained in the sense that it
can be backported into older kernels.
Mhm, that sounds like a little overkill to me.
Drivers can already import the DMA-bufs all by them selves without the
help of the DRM functions. See amdgpu for an example.
Daniel also already noted to me that he sees the DRM helper as a bit
questionable middle layer.
Have you thought about doing that instead?
Christian.
Patches 2 and 3 update SHMEM and CMA helpers to use the new callback.
Effectively this moves the sg table setup from the PRIME helpers into
the memory managers. SHMEM now supports devices without DMA support,
so custom code can be removed from udl and g12u320.
Tested by joining/mirroring displays of udl and radeon under Gnome/X11.
v2:
* move fix to importer side (Christian, Daniel)
* update SHMEM and CMA helpers for new PRIME callbacks
Thomas Zimmermann (3):
drm: Support importing dmabufs into drivers without DMA
drm/shmem-helper: Implement struct drm_driver.gem_prime_create_object
drm/cma-helper: Implement struct drm_driver.gem_prime_create_object
drivers/gpu/drm/drm_gem_cma_helper.c | 62 ++++++++++++++-----------
drivers/gpu/drm/drm_gem_shmem_helper.c | 38 ++++++++++-----
drivers/gpu/drm/drm_prime.c | 43 +++++++++++------
drivers/gpu/drm/lima/lima_drv.c | 2 +-
drivers/gpu/drm/panfrost/panfrost_drv.c | 2 +-
drivers/gpu/drm/panfrost/panfrost_gem.c | 6 +--
drivers/gpu/drm/panfrost/panfrost_gem.h | 4 +-
drivers/gpu/drm/pl111/pl111_drv.c | 8 ++--
drivers/gpu/drm/v3d/v3d_bo.c | 6 +--
drivers/gpu/drm/v3d/v3d_drv.c | 2 +-
drivers/gpu/drm/v3d/v3d_drv.h | 5 +-
include/drm/drm_drv.h | 12 +++++
include/drm/drm_gem_cma_helper.h | 12 ++---
include/drm/drm_gem_shmem_helper.h | 6 +--
14 files changed, 120 insertions(+), 88 deletions(-)
--
2.30.1
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