[PATCH v2 0/3] drm: add SimpleDRM driver

[Noralf Trønnes]

This patchset adds the simpledrm driver by David Herrmann based on a
patchset[1] from 2014. That patchset also included patches for kicking
out simpledrm by real drivers. I have stayed away from that since it
involves another subsystem and I would probably be unable to answer any
questions about the implementation.

Two major changes in this version:

I have tried to address Daniel Vetter's concern that there's no way to
kick out/handover simpledrm to the real hw-driver. My solution relies
on the fb notifier, so I don't know how robust that actually is. I've
read that there's lot's of problems with it, at least in the drm context.
A test using the vc4 driver on Raspberry Pi successfully removed simpledrm.

Luc Verhaegen alerted me to the fact that I missed support for clocks, and
in fact more additions to the Device Tree binding document that has happen
after David wrote this driver. I lifted the code verbatim from simplefb.c.
I have not tested the functionality, but I assume it will work since I
didn't make any functional changes, only changed function and variable names.


I have tested simpledrm on a Raspberry Pi B+ with U-boot setting up the
framebuffer and producing this node (legacy, not under /chosen):

/ {
        framebuffer at 1e887000 {
                compatible = "simple-framebuffer";
                reg = <0x1e887000 0x36c600>;
                format = "r5g6b5";
                width = <1824>;
                height = <984>;
                stride = <3648>;
                status = "okay";
        };

I have only tested with fbcon and modetest (XR24,RG16).


Noralf.


Changes from version 1:
- Move platform_set_drvdata() before drm_dev_register()
- Remove drm_legacy_mmap() call.
- Set mode_config.{min,max}_{width,height} to the actual dimensions
  of the native framebuffer
- Remove plane positioning since it won't work with the simple display pipe,
  meaning sdrm_display_pipe_check() isn't necessary either
- Support the additions to the Device Tree binding document, including
  clocks, regulators and having the node under /chosen
fbdev:
- Honour remove_conflicting_framebuffers()

Changes from previous version[2]:
- Remove FB_SIMPLE=n dependency to avoid kconfig recursive error
- Changed module name to match kconfig help text: sdrm -> simpledrm
- Use drm_simple_display_pipe
- Replace deprecated drm_platform_init()
- sdrm_dumb_create(): drm_gem_object_unreference() -> *_unlocked()
- sdrm_dumb_map_offset(): drm_gem_object_lookup() remove drm_device parameter
- sdrm_drm_mmap() changes:
  Remove struct_mutex locking
  Add drm_vma_offset_{lock,unlock}_lookup()
  drm_mmap() -> drm_legacy_mmap()
- dma_buf_begin_cpu_access() doesn't require start and length anymore
- Use drm_cvt_mode() instead of open coding a mode
- Fix format conversion. In the intermediate step, store the 8/6/5 bit color
  value in the upper part of the 16-bit color variable, not the lower.
- Support clips == NULL in sdrm_dirty()
- Set mode_config.preferred_depth
- Attach mode_config.dirty_info_property to connector
fbdev:
- Remove the DRM_SIMPLEDRM_FBDEV kconfig option and use DRM_FBDEV_EMULATION
- Suspend fbcon/fbdev when the pipeline is enabled, resume in lastclose
- Add FBINFO_CAN_FORCE_OUTPUT flag so we get oops'es on the console

[1] https://lists.freedesktop.org/archives/dri-devel/2014-January/052584.html
[2] https://lists.freedesktop.org/archives/dri-devel/2014-January/052594.html


Further history:

[PATCH v4 0/6] SimpleDRM Driver
https://lists.freedesktop.org/archives/dri-devel/2013-September/044638.html

[PATCH v2 00/14] Platform Framebuffers and SimpleDRM
https://lists.freedesktop.org/archives/dri-devel/2013-July/041090.html

[RFC 0/6] SimpleDRM Driver (was: dvbe driver)
https://lists.freedesktop.org/archives/dri-devel/2013-June/040386.html

[PATCH 0/9] System Framebuffer Bus (sysfb)
https://lists.freedesktop.org/archives/dri-devel/2013-February/035013.html


Noralf Trønnes (3):
  drm: add SimpleDRM driver
  drm: simpledrm: add fbdev fallback support
  drm: simpledrm: honour remove_conflicting_framebuffers()

 drivers/gpu/drm/Kconfig                      |   2 +
 drivers/gpu/drm/Makefile                     |   1 +
 drivers/gpu/drm/simpledrm/Kconfig            |  27 ++
 drivers/gpu/drm/simpledrm/Makefile           |   5 +
 drivers/gpu/drm/simpledrm/simpledrm.h        | 129 +++++++
 drivers/gpu/drm/simpledrm/simpledrm_damage.c | 304 +++++++++++++++
 drivers/gpu/drm/simpledrm/simpledrm_drv.c    | 545 +++++++++++++++++++++++++++
 drivers/gpu/drm/simpledrm/simpledrm_fbdev.c  | 200 ++++++++++
 drivers/gpu/drm/simpledrm/simpledrm_gem.c    | 273 ++++++++++++++
 drivers/gpu/drm/simpledrm/simpledrm_kms.c    | 267 +++++++++++++
 10 files changed, 1753 insertions(+)
 create mode 100644 drivers/gpu/drm/simpledrm/Kconfig
 create mode 100644 drivers/gpu/drm/simpledrm/Makefile
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm.h
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm_damage.c
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm_drv.c
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm_fbdev.c
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm_gem.c
 create mode 100644 drivers/gpu/drm/simpledrm/simpledrm_kms.c

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