[PATCH 0/6 RFC] drm: Move vmap out of commit tail for SHMEM 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.
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. Wrapper sfor simple KMS are provides,
as all of the involved drivers are built upon simple-KMS helpers.

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

Patch 2 provides plane state for SHMEM-based shadow planes. It's a
DRM plane with BO mappings into kernel address space. The involved
helpers take care of the details.

Patches 3 to 6 convert each involved driver to the new shadow-plane
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.

Thomas Zimmermann (6):
  drm/simple-kms: Add plane-state helpers
  drm/shmem-helper: Add additional KMS helpers
  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

 drivers/gpu/drm/Kconfig                    |   7 +
 drivers/gpu/drm/Makefile                   |   1 +
 drivers/gpu/drm/drm_gem_shmem_kms_helper.c | 159 +++++++++++++++++++++
 drivers/gpu/drm/drm_simple_kms_helper.c    |  40 +++++-
 drivers/gpu/drm/mgag200/Kconfig            |   1 +
 drivers/gpu/drm/mgag200/mgag200_mode.c     |  25 ++--
 drivers/gpu/drm/tiny/Kconfig               |   6 +-
 drivers/gpu/drm/tiny/cirrus.c              |  45 +++---
 drivers/gpu/drm/tiny/gm12u320.c            |  30 ++--
 drivers/gpu/drm/udl/Kconfig                |   1 +
 drivers/gpu/drm/udl/udl_modeset.c          |  36 ++---
 include/drm/drm_gem_shmem_kms_helper.h     |  56 ++++++++
 include/drm/drm_simple_kms_helper.h        |  28 ++++
 13 files changed, 353 insertions(+), 82 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_gem_shmem_kms_helper.c
 create mode 100644 include/drm/drm_gem_shmem_kms_helper.h


base-commit: 1e37c3960fd3910f3f65cd6927a6ebab8e8efc26
--
2.30.0