The display controller found on Rockchip SoCs supported by Rockchip DRM driver (VOP) is a bit problematic, because it does not provide hardware vblank counter. Because vblank interrupt is used to feed the software counter, the driver had custom code to wait for flip completion to avoid race between atomic flush and vblank interrupt handler.
This, however, brought a different set of issues. In fact, even with the custom wait code, there is stil a race between the handler and driver state update (of the values used to compare with registers to determine if flip has completed). On top of that, legacy cursor updates are not implemented properly and have to wait for vblank to complete, which is against the API specification.
This series attempts to clean up the driver from this custom waiting code, eliminating related races and bringing correct handling of legacy cursor plane. It also gives a nice effect of more than 100 lines of code removed.
This is a forward port of patches from 4.4 kernel used by ChromiumOS and tested there. Even though the code base has not changed significantly, it would be nice if someone with proper testing environment could give them a try.
Based on for-next branch of Sean Paul's dogwood tree: https://cgit.freedesktop.org/~seanpaul/dogwood/log/?h=for-next git://people.freedesktop.org/~seanpaul/dogwood
Tomasz Figa (8): drm/rockchip: Clear interrupt status bits before enabling drm/rockchip: Get rid of some unnecessary code drm/rockchip: Avoid race with vblank count increment drm/rockchip: Unreference framebuffers from flip work drm/rockchip: Replace custom wait_for_vblanks with helper drm/rockchip: Do not enable vblank without event drm/rockchip: Always signal event in next vblank after cfg_done drm/rockchip: Kill vop_plane_state
drivers/gpu/drm/rockchip/rockchip_drm_drv.h | 1 - drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 64 +------ drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 247 +++++++++++----------------- 3 files changed, 95 insertions(+), 217 deletions(-)