[RFC PATCH v2 0/9] Introduce writeback connectors

From: Brian Starkey
Date: Wed Oct 26 2016 - 04:56:12 EST


Hi,

This is an updated RFC series introducing a new connector type:
DRM_MODE_CONNECTOR_WRITEBACK
See v1 here: [1]

Writeback connectors are used to expose the memory writeback engines
found in some display controllers, which can write a CRTC's
composition result to a memory buffer.
This is useful e.g. for testing, screen-recording, screenshots,
wireless display, display cloning, memory-to-memory composition.

Writeback connectors are given a WRITEBACK_FB_ID property (which acts
slightly differently to FB_ID, so gets a new name), as well as
PIXEL_FORMATS and PIXEL_FORMATS_SIZE to list the supported writeback
formats, and OUT_FENCE_PTR to be used for out-fences.

The semantics of writeback connectors have been changed significantly
since v1, based largely on Daniel's feedback. Now, a writeback
connector can only be attached to a CRTC if it has a framebuffer
attached and vice-versa. The writeback framebuffer applies only to a
single atomic commit, and userspace can never read back the value of
WRITEBACK_FB_ID. This makes writeback a "one-shot" operation, it must
be re-armed every time it is to be used.

Patch 1 introduces the actual connector type and the infrastructure
around it. Patches 2-6 add a writeback connector for mali-dp.

Patches 7-9 add support for writeback out-fences, based on Gustavo
Padovan's v5 series [2] for adding explicit fencing.

As always, I look forward to any comments.

Thanks,
Brian

[1] http://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1247574.html
[2] http://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1253822.html

Changes since v1, based on Daniel and Eric's comments:
- The writeback framebuffer is no longer persistent across commits
- Removed the client cap, made the connector report disconnected
instead
- Added drm_writeback.c for central connector initialization and
documentation
- Added support for out-fences
- Added core checks for writeback connectors, e.g. disallowing
a framebuffer with no CRTC
- Mali-DP doesn't require a full modeset to enable/disable the
writeback connector

---

Brian Starkey (8):
drm: Add writeback connector type
drm: mali-dp: Clear CVAL when leaving config mode
drm: mali-dp: Rename malidp_input_format
drm: mali-dp: Add RGB writeback formats for DP550/DP650
drm: mali-dp: Add writeback connector
drm: atomic: factor out common out-fence operations
drm: writeback: Add out-fences for writeback connectors
drm: mali-dp: Add writeback out-fence support

Liviu Dudau (1):
drm: mali-dp: Add support for writeback on DP550/DP650

Documentation/gpu/drm-kms.rst | 9 +
drivers/gpu/drm/Makefile | 2 +-
drivers/gpu/drm/arm/Makefile | 1 +
drivers/gpu/drm/arm/malidp_crtc.c | 21 +++
drivers/gpu/drm/arm/malidp_drv.c | 28 +++-
drivers/gpu/drm/arm/malidp_drv.h | 7 +
drivers/gpu/drm/arm/malidp_hw.c | 149 +++++++++++++----
drivers/gpu/drm/arm/malidp_hw.h | 27 ++-
drivers/gpu/drm/arm/malidp_mw.c | 313 +++++++++++++++++++++++++++++++++++
drivers/gpu/drm/arm/malidp_mw.h | 28 ++++
drivers/gpu/drm/arm/malidp_planes.c | 8 +-
drivers/gpu/drm/arm/malidp_regs.h | 15 ++
drivers/gpu/drm/drm_atomic.c | 218 +++++++++++++++++++++---
drivers/gpu/drm/drm_atomic_helper.c | 8 +
drivers/gpu/drm/drm_connector.c | 4 +-
drivers/gpu/drm/drm_writeback.c | 237 ++++++++++++++++++++++++++
include/drm/drm_atomic.h | 3 +
include/drm/drm_connector.h | 26 +++
include/drm/drm_crtc.h | 20 +++
include/drm/drm_writeback.h | 21 +++
include/uapi/drm/drm_mode.h | 1 +
21 files changed, 1076 insertions(+), 70 deletions(-)
create mode 100644 drivers/gpu/drm/arm/malidp_mw.c
create mode 100644 drivers/gpu/drm/arm/malidp_mw.h
create mode 100644 drivers/gpu/drm/drm_writeback.c
create mode 100644 include/drm/drm_writeback.h

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1.7.9.5