Den 04.07.2019 13.10, skrev Thomas Zimmermann: > Hi > > Am 04.07.19 um 12:18 schrieb Noralf Trønnes: >> >> >> Den 04.07.2019 09.43, skrev Thomas Zimmermann: >>> Hi >>> >>> Am 03.07.19 um 21:27 schrieb 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? >>> >>> Fbdev emulation is special wrt framebuffer setup and there's no way to >>> distinguish a regular FB from the fbdev's FB. I've been trying >>> drm_fbdev_generic_shadow_setup(), but ended up duplicating >>> functionality. The problem was that we cannot get state-flag arguments >>> into drm_fb_helper_generic_probe(). >>> >>> There already is struct mode_config.prefer_shadow. It signals shadow FB >>> rendering to userspace. The easiest solution is to add >>> prefer_shadow_fbdev as well. If either flag is true, fbdev emulation >>> would enable shadow buffering. >> >> How about something like this: > > I had something like that in mind, but maybe without a separate > function. I'll post my variant as part of the patch set's next iteration. > <snip> >>> >>> I'm not sure if we should check for the dirty() callback at all. >>> >> >> Hm, why do you think that? > > Drivers may already come with their own shadow buffer. Cirrus is an > example of that. It uses shmem buffer objects as shadow fbs and > internally updates the device frame buffer in its dirty callback. Using > dirty() to select the shadow fbdev adds another buffer (and another > memcpy) for no reason. Cirruc uses shmem buffers and they won't work with fbdev defio (both use page->lru). shmem is the reason I added shadow buffering to generic fbdev in the first place. It will now work with whatever backing buffer the driver uses, as long as it can provide a virtual address on the dumb buffer (not the case with rockchip for instance, due to limited virtual address space). Noralf. > > Best regards > Thomas > >> The thing with fbdev defio is that it only supports kmalloc and vmalloc >> allocated memory (page->lru is avail.). This means that only the CMA >> drivers can use defio without shadow memory. To keep things simple >> everyone with a dirty() callback gets a shadow buffer. >> >> Noralf. >> >>> Best regards >>> Thomas >>> >>>> 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 >>>>> >>>> _______________________________________________ >>>> dri-devel mailing list >>>> dri-devel@xxxxxxxxxxxxxxxxxxxxx >>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel >>>> >>> > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
