[Mesa-dev] [PATCH 14/30] intel/isl: Add an enum for describing auxiliary compression state
Pohjolainen, Topi
topi.pohjolainen at gmail.com
Tue May 30 08:43:31 UTC 2017
On Fri, May 26, 2017 at 04:30:18PM -0700, Jason Ekstrand wrote:
> This enum describes all of the states that a auxiliary compressed
> surface can have. All of the states as well as normative language for
> referring to each of the compression operations is provided in the
> truly colossal comment for the new isl_aux_state enum. There is also
> a diagram showing how surfaces move between the different states.
> ---
> src/intel/isl/isl.h | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 142 insertions(+)
>
> diff --git a/src/intel/isl/isl.h b/src/intel/isl/isl.h
> index b9d8fa8..df6d3e3 100644
> --- a/src/intel/isl/isl.h
> +++ b/src/intel/isl/isl.h
> @@ -560,6 +560,148 @@ enum isl_aux_usage {
> ISL_AUX_USAGE_CCS_E,
> };
>
> +/**
> + * Enum for keeping track of the state an auxiliary compressed surface.
> + *
> + * For any given auxiliary surface compression format (HiZ, CCS, or MCS), any
> + * given slice (lod + array layer) can be in one of the six states described
> + * by this enum. Draw and resolve operations may cause the slice to change
> + * from one state to another. The six valid states are:
> + *
> + * 1) Clear: In this state, each block in the auxiliary surface contains a
> + * magic value that indicates that the block is in the clear state. If
> + * a block is in the clear state, it's values in the primary surface are
> + * ignored and the color of the samples in the block is taken either the
> + * RENDER_SURFACE_STATE packet for color or 3DSTATE_CLEAR_PARAMS for
> + * depth. Since neither the primary surface nor the auxiliary surface
> + * contains the clear value, the surface can be cleared to a different
> + * color by simply changing the clear color without modifying either
> + * surface.
> + *
> + * 2) Compressed w/ Clear: In this state, neither the auxiliary surface
> + * nor the primary surface has a complete representation of the data.
> + * Instead, both surfaces must be used together or else rendering
> + * corruption may occur. Depending on the auxiliary compression format
> + * and the data, any given block in the primary surface may contain all,
> + * some, or none of the data required to reconstruct the actual sample
> + * values. Blocks may also be in the clear state (see Clear) and have
> + * their value taken from outside the surface.
> + *
> + * 3) Compressed w/o Clear: This state is identical to the state above
> + * except that no blocks are in the clear state. In this state, all of
> + * the data required to reconstruct the final sample values is contained
> + * in the auxiliary and primary surface and the clear value is not
> + * considered.
> + *
> + * 4) Resolved: In this state, the primary surface contains 100% of the
> + * data. The auxiliary surface is also valid so the surface can be
> + * validly used with or without aux enabled. The auxiliary surface may,
> + * however, contain non-trivial data and any update to the primary
> + * surface with aux disabled will cause the two to get out of sync.
> + *
> + * 5) Pass-through: In this state, the primary surface contains 100% of the
> + * data and every block in the auxiliary surface contains a magic value
> + * which indicates that the auxiliary surface should be ignored and the
> + * only the primary surface should be considered. Updating the primary
> + * surface without aux works fine and can be done repeatedly in this
> + * mode. Writing to a surface in pass-through mode with aux enabled may
> + * cause the auxiliary buffer to contain non-trivial data and no longer
> + * be in the pass-through state.
> + *
> + * 5) Aux Invalid: In this state, the primary surface contains 100% of the
> + * data and the auxiliary surface is completely bogus. Any attempt to
> + * use the auxiliary surface is liable to result in rendering
> + * corruption. The only thing that one can do to re-enable aux once
> + * this state is reached is to use an ambiguate pass to transition into
> + * the pass-through state.
> + *
> + * Drawing with or without aux enabled may implicitly cause the surface to
> + * transition between these states. There are also four types of "resolve"
> + * operations which cause an explicit transition:
> + *
> + * 1) Fast Clear: This operation writes the magic "clear" value to the
> + * auxiliary surface. This operation will safely transition any slice
> + * of a surface from any state to the clear state so long as the entire
> + * slice is fast cleared at once.
> + *
> + * 2) Full Resolve: This operation combines the auxiliary surface data
> + * with the primary surface data and writes the result to the primary.
> + * For CCS resolves, this operation is destructive in the sense that it
> + * also sets the auxiliary surface to the pass-through mode. For HiZ,
In the diagram below this ends up in "Resolved" state which in the diagram
is not the same as "Passthrough". It stroke me odd that "Draw w/o Aux"
transitions it to "Aux Invalid". This is true for HIZ but not for CCS. In case
of CCS one should actually be in "Passthrough" where "Draw w/o Aux" maintains
the state.
Other than that this is really nice piece of documentation!!
> + * it is not destructive.
> + *
> + * 3) Partial Resolve: This operation considers blocks which are in the
> + * "clear" state and writes the clear value directly into the primary or
> + * auxiliary surface. Once this operation completes, the surface is
> + * still compressed but no longer references the clear color. This
> + * operation is only available for CCS.
> + *
> + * 4) Ambiguate: This operation throws away the current auxiliary data and
> + * replaces it with the magic pass-through value. If an ambiguate
> + * operation is performed when the primary surface does not contain 100%
> + * of the data, data will be lost. This operation is only implemented
> + * in hardware for depth where it is called a HiZ resolve.
> + *
> + * Not all operations are valid or useful in all states. The diagram below
> + * contains a complete description of the states and all valid and useful
> + * transitions except clear.
> + *
> + * Draw w/ Aux
> + * +----------+
> + * | |
> + * | +-------------+ Draw w/ Aux +-------------+
> + * +------>| Compressed |<---------------------| Clear |
> + * | w/ Clear | | |
> + * +-------------+ +-------------+
> + * | | |
> + * Partial | | |
> + * Resolve | | Full Resolve |
> + * | +----------------------------+ | Full
> + * | | | Resolve
> + * Draw w/ aux | | |
> + * +----------+ | | |
> + * | | \|/ \|/ \|/
> + * | +-------------+ Full Resolve +-------------+
> + * +------>| Compressed |--------------------->| Resolved |
> + * | w/o Clear |<---------------------| |
> + * +-------------+ Draw w/ Aux +-------------+
> + * /|\ | |
> + * | Draw | | Draw
> + * | w/ Aux | | w/o Aux
> + * | Ambiguate | |
> + * | +----------------------------+ |
> + * Draw w/o Aux | | | Draw w/o Aux
> + * +----------+ | | | +----------+
> + * | | | \|/ \|/ | |
> + * | +-------------+ Ambiguate +-------------+ |
> + * +------>| Pass- |<---------------------| Aux |<------+
> + * | through | | Invalid |
> + * +-------------+ +-------------+
> + *
> + *
> + * As referenced in the description of the different operations above, not all
> + * auxiliary surface formats actually support all of the above modes. With
> + * HiZ, for instance, does not have a partial resolve operation so the two
> + * "compressed" modes are the same. With CCS, the resolve operation is
> + * destructive and takes you directly to passthrough so the "resolved" state
> + * doesn't really exist. However, if you consider the CCS resolve operation
> + * as doing a resolve and then an ambiguate, the diagram is still accurate.
> + */
> +enum isl_aux_state {
> + /** Describes the Clear state */
> + ISL_AUX_STATE_CLEAR = 0,
> + /** Describes the Compressed w/ Clear state */
> + ISL_AUX_STATE_COMPRESSED_CLEAR,
> + /** Describes the Compressed w/o Clear state */
> + ISL_AUX_STATE_COMPRESSED_NO_CLEAR,
> + /** Describes the Resolved state */
> + ISL_AUX_STATE_RESOLVED,
> + /** Describes the Pass-through state */
> + ISL_AUX_STATE_PASS_THROUGH,
> + /** Describes the Aux Invalid state */
> + ISL_AUX_STATE_AUX_INVALID,
> +};
> +
> /* TODO(chadv): Explain */
> enum isl_array_pitch_span {
> ISL_ARRAY_PITCH_SPAN_FULL,
> --
> 2.5.0.400.gff86faf
>
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