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.
I have done my best to bring simpledrm up to speed. However I was unable to loose drm_legacy_mmap() in sdrm_drm_mmap() since I don't understand much of the gem code.
I was left with some questions after doing this:
- Is there any reason why simpledrm can't use drm_gem_cma_helper? One obvious difference is that of contiguous memory allocation:
sdrm_gem_get_pages(): obj->pages = drm_malloc_ab(num, sizeof(*obj->pages)); for (i = 0; i < num; ++i) { obj->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO); obj->vmapping = vmap(obj->pages, num, 0, PAGE_KERNEL);
drm_gem_cma_create(): cma_obj->vaddr = dma_alloc_wc(drm->dev, size, &cma_obj->paddr, GFP_KERNEL | __GFP_NOWARN);
- Could we set this range to the actual width/height of the native framebuffer?
sdrm_drm_modeset_init(): ddev->mode_config.min_width = 1; ddev->mode_config.min_height = 1; ddev->mode_config.max_width = 8192; ddev->mode_config.max_height = 8192;
- Is there a usecase for offsetting the dumb buffer when blitted onto the native buffer?
sdrm_blit(): /* get scanout offsets */ xoff = 0; yoff = 0; if (sdrm->pipe.plane.fb == fb) { xoff = sdrm->pipe.crtc.x; yoff = sdrm->pipe.crtc.y; }
I have tested simpledrm on a Raspberry Pi B+ with U-boot setting up the framebuffer and producing this node:
framebuffer@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 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 (2): drm: add SimpleDRM driver drm: simpledrm: add fbdev fallback support
drivers/gpu/drm/Kconfig | 2 + drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/simpledrm/Kconfig | 22 ++ drivers/gpu/drm/simpledrm/Makefile | 5 + drivers/gpu/drm/simpledrm/simpledrm.h | 111 ++++++++++ drivers/gpu/drm/simpledrm/simpledrm_damage.c | 314 +++++++++++++++++++++++++++ drivers/gpu/drm/simpledrm/simpledrm_drv.c | 298 +++++++++++++++++++++++++ drivers/gpu/drm/simpledrm/simpledrm_fbdev.c | 160 ++++++++++++++ drivers/gpu/drm/simpledrm/simpledrm_gem.c | 276 +++++++++++++++++++++++ drivers/gpu/drm/simpledrm/simpledrm_kms.c | 288 ++++++++++++++++++++++++ 10 files changed, 1477 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
-- 2.8.2