Re: [PATCH v5 00/19] R-Car DU display writeback support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Brian,

On Fri, Feb 22, 2019 at 02:04:10PM +0000, Brian Starkey wrote:
> On Thu, Feb 21, 2019 at 12:31:53PM +0200, Laurent Pinchart wrote:
> > Hello everybody,
> > 
> > This patch series implements display writeback support for the R-Car
> > Gen3 platforms in the VSP1 and DU drivers.
> > 
> > Patches 01/19 to 11/19 prepare the VSP1 driver for writeback support
> > with all the necessary plumbing, including extensions of the API between
> > the VSP1 and DU drivers.
> > 
> > Compared to v4 the major change is the move from V4L2 to DRM writeback
> > connectors for the userspace API. This has caused a few issues with
> > writeback support to be uncovered, and they are addressed by patches
> > 12/19 to 14/19. Patch 15/19 is an unrelated drive-by fix.
> > 
> > Patches 16/19 to 18/19 then perform refactoring of the DU driver, to
> > finally add writeback support in patch 19/19.
> > 
> > The writeback pixel format is restricted to RGB, due to the VSP1
> > outputting RGB to the display and lacking a separate colour space
> > conversion unit for writeback. The resolution can be freely picked by
> > will result in cropping or composing, not scaling.
> 
> I think this sentence about cropping doesn't match the implementation,
> as you're checking the framebuffer size against the mode.

That's true, it was different when using V4L2, but now the resolution is
fixed.

> We want to enable scaling/composing on writeback (which our HW can
> do). I thought we'd add WRITEBACK_X/Y/W/H properties to set the
> destination buffer coordinates. One of our team is working on that
> now.
> 
> We don't have cropping, but I thought that could be achieved by
> exposing CRTC_X/Y/W/H on writeback connectors.

I don't have a use case from cropping or composing writeback at the
moment, but such an API would likely work.

> > Writeback requests are queued to the hardware on page flip (atomic
> > flush), and complete at the next vblank. This means that a queued
> > writeback buffer will not be processed until the next page flip, but
> > once it starts being written to by the VSP, it will complete at the next
> > vblank regardless of whether another page flip occurs at that time.
> > 
> > The code is based on a merge of the media master branch, the drm-next
> > branch and the R-Car DT next branch. For convenience patches can be
> > found at
> > 
> >         git://linuxtv.org/pinchartl/media.git v4l2/vsp1/writeback
> > 
> > Kieran Bingham (1):
> >   Revert "[media] v4l: vsp1: Supply frames to the DU continuously"
> > 
> > Laurent Pinchart (18):
> >   media: vsp1: wpf: Fix partition configuration for display pipelines
> >   media: vsp1: Replace leftover occurrence of fragment with body
> >   media: vsp1: Fix addresses of display-related registers for VSP-DL
> >   media: vsp1: Refactor vsp1_video_complete_buffer() for later reuse
> >   media: vsp1: Replace the display list internal flag with a flags field
> >   media: vsp1: dl: Support one-shot entries in the display list
> >   media: vsp1: wpf: Add writeback support
> >   media: vsp1: drm: Split RPF format setting to separate function
> >   media: vsp1: drm: Extend frame completion API to the DU driver
> >   media: vsp1: drm: Implement writeback support
> >   drm: writeback: Cleanup job ownership handling when queuing job
> >   drm: writeback: Fix leak of writeback job
> >   drm: writeback: Add job prepare and cleanup operations
> >   drm/msm: Remove prototypes for non-existing functions
> >   drm: rcar-du: Fix rcar_du_crtc structure documentation
> >   drm: rcar-du: Store V4L2 fourcc in rcar_du_format_info structure
> >   drm: rcar-du: vsp: Extract framebuffer (un)mapping to separate
> >     functions
> >   drm: rcar-du: Add writeback support for R-Car Gen3
> > 
> >  drivers/gpu/drm/arm/malidp_mw.c             |   3 +-
> >  drivers/gpu/drm/drm_atomic_helper.c         |  11 ++
> >  drivers/gpu/drm/drm_atomic_state_helper.c   |   4 +
> >  drivers/gpu/drm/drm_atomic_uapi.c           |  31 +--
> >  drivers/gpu/drm/drm_writeback.c             |  71 ++++++-
> >  drivers/gpu/drm/msm/msm_drv.h               |   2 -
> >  drivers/gpu/drm/rcar-du/Kconfig             |   4 +
> >  drivers/gpu/drm/rcar-du/Makefile            |   3 +-
> >  drivers/gpu/drm/rcar-du/rcar_du_crtc.h      |   9 +-
> >  drivers/gpu/drm/rcar-du/rcar_du_kms.c       |  37 ++++
> >  drivers/gpu/drm/rcar-du/rcar_du_kms.h       |   1 +
> >  drivers/gpu/drm/rcar-du/rcar_du_vsp.c       | 121 ++++++------
> >  drivers/gpu/drm/rcar-du/rcar_du_vsp.h       |  17 ++
> >  drivers/gpu/drm/rcar-du/rcar_du_writeback.c | 203 ++++++++++++++++++++
> >  drivers/gpu/drm/rcar-du/rcar_du_writeback.h |  39 ++++
> >  drivers/gpu/drm/vc4/vc4_txp.c               |   2 +-
> >  drivers/media/platform/vsp1/vsp1_dl.c       | 127 ++++++++++--
> >  drivers/media/platform/vsp1/vsp1_dl.h       |   8 +-
> >  drivers/media/platform/vsp1/vsp1_drm.c      |  92 ++++++---
> >  drivers/media/platform/vsp1/vsp1_drm.h      |   2 +-
> >  drivers/media/platform/vsp1/vsp1_drv.c      |  15 ++
> >  drivers/media/platform/vsp1/vsp1_pipe.c     |   5 +
> >  drivers/media/platform/vsp1/vsp1_pipe.h     |   1 +
> >  drivers/media/platform/vsp1/vsp1_regs.h     |   6 +-
> >  drivers/media/platform/vsp1/vsp1_rwpf.h     |   2 +
> >  drivers/media/platform/vsp1/vsp1_video.c    |  49 +++--
> >  drivers/media/platform/vsp1/vsp1_wpf.c      |  68 +++++--
> >  include/drm/drm_modeset_helper_vtables.h    |   7 +
> >  include/drm/drm_writeback.h                 |  30 ++-
> >  include/media/vsp1.h                        |  19 +-
> >  30 files changed, 790 insertions(+), 199 deletions(-)
> >  create mode 100644 drivers/gpu/drm/rcar-du/rcar_du_writeback.c
> >  create mode 100644 drivers/gpu/drm/rcar-du/rcar_du_writeback.h

-- 
Regards,

Laurent Pinchart
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