Documents the Flat-CCS feature and kernel handling required along with modifiers used.
Signed-off-by: Ramalingam C ramalingam.c@intel.com cc: Simon Ser contact@emersion.fr cc: Pekka Paalanen ppaalanen@gmail.com --- drivers/gpu/drm/i915/gt/intel_migrate.c | 47 +++++++++++++++++++++++++ 1 file changed, 47 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c index 0bed01750884..ad5a28da1c6a 100644 --- a/drivers/gpu/drm/i915/gt/intel_migrate.c +++ b/drivers/gpu/drm/i915/gt/intel_migrate.c @@ -491,6 +491,53 @@ intel_context_migrate_copy(struct intel_context *ce, return err; }
+/** + * DOC: Flat-CCS - Memory compression for Local memory + * + * 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. + * + * Flat CCS data needs to be cleared when a lmem object is allocated. + * And CCS data can be copied in and out of CCS region through + * XY_CTRL_SURF_COPY_BLT. CPU can't access the CCS data directly. + * + * When we exaust the lmem, if the object's placements support smem, then we can + * directly decompress the compressed lmem object into smem and start using it + * from smem itself. + * + * But when we need to swapout the compressed lmem object into a smem region + * though objects' placement doesn't support smem, then we copy the lmem content + * as it is into smem region along with ccs data (using XY_CTRL_SURF_COPY_BLT). + * When the object is referred, lmem content will be swaped in along with + * restoration of the CCS data (using XY_CTRL_SURF_COPY_BLT) at corresponding + * location. + * + * + * Flat-CCS Modifiers for different compression formats + * ---------------------------------------------------- + * + * I915_FORMAT_MOD_F_TILED_DG2_RC_CCS - used to indicate the buffers of Flat CCS + * render compression formats. Though the general layout is same as + * I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS, new hashing/compression algorithm is + * used. Render compression uses 128 byte compression blocks + * + * I915_FORMAT_MOD_F_TILED_DG2_MC_CCS -used to indicate the buffers of Flat CCS + * media compression formats. Though the general layout is same as + * I915_FORMAT_MOD_Y_TILED_GEN12_MC_CCS, new hashing/compression algorithm is + * used. Media compression uses 256 byte compression blocks. + * + * I915_FORMAT_MOD_F_TILED_DG2_RC_CCS_CC - used to indicate the buffers of Flat + * CCS clear color render compression formats. Unified compression format for + * clear color render compression. The genral layout is a tiled layout using + * 4Kb tiles i.e Tile4 layout. + */ + static inline u32 *i915_flush_dw(u32 *cmd, u64 dst, u32 flags) { /* Mask the 3 LSB to use the PPGTT address space */