[PATCH 0/5] Unmappable DRM client buffers for fbdev emulation

[Noralf Trønnes]

Den 03.07.2019 10.32, skrev Thomas Zimmermann:
> DRM client buffers are permanently mapped throughout their lifetime. This
> prevents us from using generic framebuffer emulation for devices with
> small dedicated video memory, such as ast or mgag200. With fb buffers
> permanently mapped, such devices often won't have enougth space left to
> display other content (e.g., X11).
> 
> This patch set introduces unmappable DRM client buffers for framebuffer
> emulation with shadow buffers. While the shadow buffer remains in system
> memory permanently, the respective buffer object will only be mapped briefly
> during updates from the shadow buffer. Hence, the driver can relocate he
> buffer object among memory regions as needed.
> 
> The default behoviour for DRM client buffers is still to be permanently
> mapped.
> 
> The patch set converts ast and mgag200 to generic framebuffer emulation
> and removes a large amount of framebuffer code from these drivers. For
> bochs, a problem was reported where the driver could not display the console
> because it was pinned in system memory. [1] The patch set fixes this bug
> by converting bochs to use the shadow fb.
> 
> The patch set has been tested on ast and mga200 HW.
> 

I've been thinking, this enables dirty tracking in DRM userspace for
these drivers since the dirty callback is now set on all framebuffers.
Is this OK? Should we add a drm_fbdev_generic_shadow_setup() that sets a
flag enabling the shadow buffer instead?

Really nice diffstat by the way :-)

Noralf.

> [1] https://lists.freedesktop.org/archives/dri-devel/2019-June/224423.html
> 
> Thomas Zimmermann (5):
>   drm/client: Support unmapping of DRM client buffers
>   drm/fb-helper: Unmap BO for shadow-buffered framebuffer console
>   drm/ast: Replace struct ast_fbdev with generic framebuffer emulation
>   drm/bochs: Use shadow buffer for bochs framebuffer console
>   drm/mgag200: Replace struct mga_fbdev with generic framebuffer
>     emulation
> 
>  drivers/gpu/drm/ast/Makefile           |   2 +-
>  drivers/gpu/drm/ast/ast_drv.c          |  22 +-
>  drivers/gpu/drm/ast/ast_drv.h          |  17 --
>  drivers/gpu/drm/ast/ast_fb.c           | 341 -------------------------
>  drivers/gpu/drm/ast/ast_main.c         |  30 ++-
>  drivers/gpu/drm/ast/ast_mode.c         |  21 --
>  drivers/gpu/drm/bochs/bochs_kms.c      |   2 +-
>  drivers/gpu/drm/drm_client.c           |  71 ++++-
>  drivers/gpu/drm/drm_fb_helper.c        |  14 +-
>  drivers/gpu/drm/mgag200/Makefile       |   2 +-
>  drivers/gpu/drm/mgag200/mgag200_drv.h  |  19 --
>  drivers/gpu/drm/mgag200/mgag200_fb.c   | 309 ----------------------
>  drivers/gpu/drm/mgag200/mgag200_main.c |  61 +++--
>  drivers/gpu/drm/mgag200/mgag200_mode.c |  27 --
>  include/drm/drm_client.h               |   3 +
>  15 files changed, 154 insertions(+), 787 deletions(-)
>  delete mode 100644 drivers/gpu/drm/ast/ast_fb.c
>  delete mode 100644 drivers/gpu/drm/mgag200/mgag200_fb.c
> 
> --
> 2.21.0
>