Rework of my previous patchset which added support for GEM buffers backed by non-coherent memory to the ingenic-drm driver.
Having GEM buffers backed by non-coherent memory is interesting in the particular case where it is faster to render to a non-coherent buffer then sync the data cache, than to render to a write-combine buffer, and (by extension) much faster than using a shadow buffer. This is true for instance on some Ingenic SoCs, where even simple blits (e.g. memcpy) are about three times faster using this method.
For the record, the previous patchset was accepted for 5.10 then had to be reverted, as it conflicted with some changes made to the DMA API.
This new patchset is pretty different as it adds the functionality to the DRM core. The first three patches add variants to existing functions but with the "non-coherent memory" twist, exported as GPL symbols. The fourth patch adds a function to be used with the damage helpers. Finally, the last patch adds support for non-coherent GEM buffers to the ingenic-drm driver. The functionality is enabled through a module parameter, and is disabled by default.
Cheers, -Paul
Paul Cercueil (5): drm: Add and export function drm_gem_cma_create_noncoherent drm: Add and export function drm_gem_cma_dumb_create_noncoherent drm: Add and export function drm_gem_cma_mmap_noncoherent drm: Add and export function drm_gem_cma_sync_data drm/ingenic: Add option to alloc cached GEM buffers
drivers/gpu/drm/drm_gem_cma_helper.c | 223 +++++++++++++++++++--- drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 49 ++++- drivers/gpu/drm/ingenic/ingenic-drm.h | 4 + drivers/gpu/drm/ingenic/ingenic-ipu.c | 14 +- include/drm/drm_gem_cma_helper.h | 13 ++ 5 files changed, 273 insertions(+), 30 deletions(-)