[PATCH v3 0/7] drm: Move vmap out of commit tail for SHMEM-based drivers

[Thomas Zimmermann]

Several SHMEM-based drivers use the BO as shadow buffer for the real
framebuffer memory. Damage handling requires a vmap of the BO memory.
But vmap/vunmap can acquire the dma-buf reservation lock, which is not
allowed in commit tails.

This patchset introduces a set of helpers that implement vmap/vunmap
in the plane's prepare_fb and cleanup_fb; and provide the mapping's
address to commit-tail functions. Wrappers for simple KMS are provides,
as all of the involved drivers are built upon simple-KMS helpers.

All patches have been acked already. v3 only fixes a few typos in the
documentation.

Patch 1 adds the support for private plane state to the simple-KMS
helper library.

Patches 2 and 3 provide plane state for shadow-buffered planes. It's a
DRM plane with BO mappings into kernel address space. The involved
helpers take care of the details. The code is independent from GEM
SHMEM and can be used with other shadow-buffered planes. I put all
this in a new file. In a later patch, drm_gem_fb_prepare_fb() et al
could be moved there as well.

Patches 4 to 7 convert each involved driver to the new helpers. The
vmap operations are being removed from commit-tail functions. An
additional benefit is that vmap errors are now detected before the
commit starts. The original commit-tail functions could not
handle failed vmap operations.

I smoke-tested the code by running fbdev, Xorg and weston with the
converted mgag200 driver.

v3:
	* documentation fixes
v2:
	* export drm_gem_vmap()/_vunmap() (kernel test robot)
	* make duplicate_state interface compatible with
	  struct drm_plane_funcs

Thomas Zimmermann (7):
  drm/simple-kms: Add plane-state helpers
  drm/gem: Export drm_gem_vmap() and drm_gem_vunmap()
  drm: Add additional atomic helpers for shadow-buffered planes
  drm/mgag200: Move vmap out of commit tail
  drm/cirrus: Move vmap out of commit tail
  drm/gm12u320: Move vmap out of commit tail
  drm/udl: Move vmap out of commit tail

 Documentation/gpu/drm-kms-helpers.rst   |  12 ++
 drivers/gpu/drm/Makefile                |   3 +-
 drivers/gpu/drm/drm_gem.c               |   2 +
 drivers/gpu/drm/drm_gem_atomic_helper.c | 208 ++++++++++++++++++++++++
 drivers/gpu/drm/drm_simple_kms_helper.c |  40 ++++-
 drivers/gpu/drm/mgag200/mgag200_mode.c  |  23 +--
 drivers/gpu/drm/tiny/cirrus.c           |  43 ++---
 drivers/gpu/drm/tiny/gm12u320.c         |  28 ++--
 drivers/gpu/drm/udl/udl_modeset.c       |  34 ++--
 include/drm/drm_gem_atomic_helper.h     |  73 +++++++++
 include/drm/drm_simple_kms_helper.h     |  27 +++
 11 files changed, 412 insertions(+), 81 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_gem_atomic_helper.c
 create mode 100644 include/drm/drm_gem_atomic_helper.h


base-commit: efb1b1293b064512f7c47537e35ad14a05a05c84
prerequisite-patch-id: c2b2f08f0eccc9f5df0c0da49fa1d36267deb11d
--
2.30.0