[Mesa-dev] [PATCH 14/30] intel/isl: Add an enum for describing auxiliary compression state

Nanley Chery nanleychery at gmail.com
Fri Jun 2 21:31:01 UTC 2017


On Fri, Jun 02, 2017 at 01:05:47PM -0700, Jason Ekstrand wrote:
> On Fri, Jun 2, 2017 at 12:57 PM, Nanley Chery <nanleychery at gmail.com> wrote:
> 
> > On Fri, May 26, 2017 at 04:30:18PM -0700, Jason Ekstrand wrote:
> > > This enum describes all of the states that a auxiliary compressed
> >                                              ^
> >                                              an
> > > 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
> >          ^
> >          6
> > > + *       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:
> > > + *
> >
> > I'm not sure why Fast Clear is described as a "resolve" operation.  To
> > me, "resolve" operations are those which make data in one buffer match
> > the data in another buffer. Perhaps you can clarify this?
> >
> 
> How about "auxiliary compression operation"?  Yeah, resolve is a bit of a
> bad name.
> 
> --Jason
> 
> 

That's better. With those 3 issues fixed, this patch is
Reviewed-by: Nanley Chery <nanley.g.chery at intel.com>

> > > + *    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,
> > > + *       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.
> > > + */
> >
> > This comment is very helpful.
> >


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