On Xe-HP and later devices, we use dedicated compression control state (CCS) stored in local memory for each surface, to support the 3D and media compression formats.
The memory required for the CCS of the entire local memory is 1/256 of the local memory size. So before the kernel boot, the required memory is reserved for the CCS data and a secure register will be programmed with the CCS base address
So when we allocate a object in local memory we dont need to explicitly allocate the space for ccs data. But when we evict the obj into the smem to hold the compression related data along with the obj we need smem space of obj_size + (obj_size/256).
Hence when we create smem for an obj with lmem placement possibility we create with the extra space.
When we are swapping out the local memory obj on flat-ccs capable platform, we need to capture the ccs data too along with main meory and we need to restore it when we are swapping in the content.
When lmem object is swapped into a smem obj, smem obj will have the extra pages required to hold the ccs data corresponding to the lmem main memory. So main memory of lmem will be copied into the initial pages of the smem and then ccs data corresponding to the main memory will be copied to the subsequent pages of smem.
Swapin happens exactly in reverse order. First main memory of lmem is restored from the smem's initial pages and the ccs data will be restored from the subsequent pages of smem.
Extracting and restoring the CCS data is done through a special cmd called XY_CTRL_SURF_COPY_BLT
v8 and v9: New patch for return value fix Fix a return error code
Test-with: 20220405141050.16037-1-ramalingam.c@intel.com
Ramalingam C (9): drm/i915/gt: use engine instance directly for offset drm/i915/gt: Use XY_FAST_COLOR_BLT to clear obj on graphics ver 12+ drm/i915/gt: Optimize the migration and clear loop drm/i915/gt: Pass the -EINVAL when emit_pte doesn't update any PTE drm/i915/gt: Clear compress metadata for Flat-ccs objects drm/i915/selftest_migrate: Consider the possible roundup of size drm/i915/selftest_migrate: Check CCS meta data clear drm/i915/gem: Add extra pages in ttm_tt for ccs data drm/i915/migrate: Evict and restore the flatccs capable lmem obj
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 30 +- drivers/gpu/drm/i915/gt/intel_gpu_commands.h | 21 + drivers/gpu/drm/i915/gt/intel_migrate.c | 387 +++++++++++++++++-- drivers/gpu/drm/i915/gt/selftest_migrate.c | 253 ++++++++++-- 4 files changed, 631 insertions(+), 60 deletions(-)