There were some small rounding errors in when clamping with 1.0001 and 0.9999 scaling, solve these and add a testcase for drm helpers, which can be used to prevent more of these errors in the future.
The new handling in drm_rect_clip_scaled rounds scaling towards 1.0x but because the rounding error is only 1 pixel with the new math, we won't ever get in a situation where we go from 1.001 to .999
Maarten Lankhorst (5): drm/rect: Round above 1 << 16 upwards to correct scale calculation functions. drm/rect: Handle rounding errors in drm_rect_clip_scaled, v3. drm/i915: Do not adjust scale when out of bounds, v2. drm/selftests: Rename the Kconfig option to CONFIG_DRM_DEBUG_SELFTEST drm/selftests: Add drm helper selftest
drivers/gpu/drm/Kconfig | 9 +- drivers/gpu/drm/Makefile | 2 +- drivers/gpu/drm/drm_atomic_helper.c | 2 +- drivers/gpu/drm/drm_rect.c | 62 ++++- drivers/gpu/drm/i915/intel_sprite.c | 144 +++------- drivers/gpu/drm/selftests/Makefile | 2 +- .../gpu/drm/selftests/drm_helper_selftests.h | 9 + drivers/gpu/drm/selftests/test-drm-helper.c | 247 ++++++++++++++++++ include/drm/drm_rect.h | 3 +- 9 files changed, 348 insertions(+), 132 deletions(-) create mode 100644 drivers/gpu/drm/selftests/drm_helper_selftests.h create mode 100644 drivers/gpu/drm/selftests/test-drm-helper.c