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uapi/drm/i915: Document memory residency and Flat-CCS capability of obj 

Capture the impact of memory region preference list of the objects, on
their memory residency and Flat-CCS capability.

v2:
  Fix the Flat-CCS capability of an obj with {lmem, smem} preference
  list [Thomas]
v3:
  Reworded the doc [Matt]
v4:
  Fixed Typos and spelling mistakes [Tvrtko, Joonas]

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
cc: Matthew Auld <matthew.auld@intel.com>
cc: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
cc: Daniel Vetter <daniel.vetter@ffwll.ch>
cc: Jon Bloomfield <jon.bloomfield@intel.com>
cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
cc: Kenneth Graunke <kenneth@whitecape.org>
cc: mesa-dev@lists.freedesktop.org
cc: Jordan Justen <jordan.l.justen@intel.com>
cc: Tony Ye <tony.ye@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220502141508.2327-1-ramalingam.c@intel.com
This commit is contained in:
Ramalingam C 2022-05-02 19:45:08 +05:30
parent e180a7b218
commit a50794f26f
1 changed files with 16 additions and 0 deletions
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16
include/uapi/drm/i915_drm.h
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@ -3443,6 +3443,22 @@ struct drm_i915_gem_create_ext {
* At which point we get the object handle in &drm_i915_gem_create_ext.handle,
* along with the final object size in &drm_i915_gem_create_ext.size, which
* should account for any rounding up, if required.
*
* Note that userspace has no means of knowing the current backing region
* for objects where @num_regions is larger than one. The kernel will only
* ensure that the priority order of the @regions array is honoured, either
* when initially placing the object, or when moving memory around due to
* memory pressure
*
* On Flat-CCS capable HW, compression is supported for the objects residing
* in I915_MEMORY_CLASS_DEVICE. When such objects (compressed) have other
* memory class in @regions and migrated (by i915, due to memory
* constraints) to the non I915_MEMORY_CLASS_DEVICE region, then i915 needs to
* decompress the content. But i915 doesn't have the required information to
* decompress the userspace compressed objects.
*
* So i915 supports Flat-CCS, on the objects which can reside only on
* I915_MEMORY_CLASS_DEVICE regions.
*/
struct drm_i915_gem_create_ext_memory_regions {
/** @base: Extension link. See struct i915_user_extension. */