Rework the fbdev deferred-I/O to not interfere with fields of struct page. Make the code more flexible and implement GEM SHMEM mmap on top of it.
This patchset removes the need for a special shadow framebuffer for fbdev mmap when using GEM SHMEM. SHMEM pages are now mmap'ed from /dev/fb directly.
Patches 2 and 3 rework the fbdev deferred I/O code. It now allows drivers to have better control of the mmap operations. All references to fields in struct page are gone. The rsp state is help in a separate pageref structure.
Patches 4 to 7 provide callbacks an helpers to implement deferred I/O with DRM drivers. Specifically, patch 6 introduces a callback to create a dumb buffer for fbdev. This will be useful for many drivers that currently cannot use generic fbdev emulation because of special placement needs of the BO, such as amdgpu or radeon. The drivers can handle the differences to regular dumb buffers in their new callback implementation.
Patch 8 extends the GEM SHMEM memory manager with a new helper for fbdev dumb-buffer creation. The returned BO has it's mmap set up to implement deferred I/O with SHMEM pages. No additional shadow buffer is requires any longer. Many drivers can immediatelly benefit from this change.
Patch 9 extends virtgpu to support fbdev dumb buffers. It's build on top of GEM SHMEM, but has some modifications that need to be implemented for fbdev as well.
There's no immediate fbdev performance improvement from this patchset. Most of all, it removes unnecessary shadow framebuffers and rsp memcpys. A shadow fb for a FullHD display is ~8 MiB, which we now save. The patches do reduce latency between drawing to the fbdev buffer to displaying on the screen. Watching a video on the fbdev console felt smoother and had less flickering.
Thomas Zimmermann (9): drm/simpledrm: Use fbdev defaults for shadow buffering fbdev: Put mmap for deferred I/O into drivers fbdev: Track deferred-I/O pages in pageref struct fbdev: Export helper for implementing page_mkwrite drm/fb-helper: Separate deferred I/O from shadow buffers drm/fb-helper: Provide callback to create fbdev dumb buffers drm/fb-helper: Provide fbdev deferred-I/O helpers drm/gem-shmem: Implement fbdev dumb buffer and mmap helpers drm/virtio: Implement dumb_create_fbdev with GEM SHMEM helpers
drivers/gpu/drm/drm_client.c | 14 +- drivers/gpu/drm/drm_crtc_internal.h | 3 + drivers/gpu/drm/drm_dumb_buffers.c | 36 +++- drivers/gpu/drm/drm_fb_helper.c | 79 +++++++-- drivers/gpu/drm/drm_gem_shmem_helper.c | 204 ++++++++++++++++++++--- drivers/gpu/drm/gud/gud_drv.c | 2 +- drivers/gpu/drm/hyperv/hyperv_drm_drv.c | 2 +- drivers/gpu/drm/mgag200/mgag200_drv.c | 2 +- drivers/gpu/drm/tiny/cirrus.c | 2 +- drivers/gpu/drm/tiny/gm12u320.c | 2 +- drivers/gpu/drm/tiny/simpledrm.c | 3 +- drivers/gpu/drm/udl/udl_drv.c | 2 +- drivers/gpu/drm/virtio/virtgpu_drv.c | 2 + drivers/gpu/drm/virtio/virtgpu_drv.h | 2 + drivers/gpu/drm/virtio/virtgpu_object.c | 54 +++++- drivers/gpu/drm/vkms/vkms_drv.c | 2 +- drivers/gpu/drm/vmwgfx/vmwgfx_fb.c | 6 +- drivers/hid/hid-picolcd_fb.c | 1 + drivers/staging/fbtft/fbtft-core.c | 6 +- drivers/video/fbdev/broadsheetfb.c | 6 +- drivers/video/fbdev/core/fb_defio.c | 211 +++++++++++++++++------- drivers/video/fbdev/core/fbmem.c | 19 +-- drivers/video/fbdev/hecubafb.c | 1 + drivers/video/fbdev/hyperv_fb.c | 6 +- drivers/video/fbdev/metronomefb.c | 6 +- drivers/video/fbdev/sh_mobile_lcdcfb.c | 12 +- drivers/video/fbdev/smscufx.c | 8 +- drivers/video/fbdev/ssd1307fb.c | 1 + drivers/video/fbdev/udlfb.c | 8 +- drivers/video/fbdev/xen-fbfront.c | 6 +- include/drm/drm_client.h | 3 +- include/drm/drm_drv.h | 27 +++ include/drm/drm_fb_helper.h | 9 + include/drm/drm_gem_shmem_helper.h | 63 ++++++- include/linux/fb.h | 12 +- 35 files changed, 668 insertions(+), 154 deletions(-)
base-commit: 710a019ad85e96e66f7d75ee7f4733cdd8a2b0d0 prerequisite-patch-id: c2b2f08f0eccc9f5df0c0da49fa1d36267deb11d prerequisite-patch-id: c67e5d886a47b7d0266d81100837557fda34cb24 prerequisite-patch-id: 6e1032c6302461624f33194c8b8f37103a3fa6ef