src/gallium/drivers/r300/r300_hyperz.c

   1 /*
   2  * Copyright 2008 Corbin Simpson <MostAwesomeDude@gmail.com>
   3  * Copyright 2009 Marek Olšák <maraeo@gmail.com>
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * on the rights to use, copy, modify, merge, publish, distribute, sub
   9  * license, and/or sell copies of the Software, and to permit persons to whom
  10  * the Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the next
  13  * paragraph) shall be included in all copies or substantial portions of the
  14  * Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
  20  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  21  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  22  * USE OR OTHER DEALINGS IN THE SOFTWARE. */
  23
  24
  25 #include "r300_hyperz.h"
  26 #include "r300_context.h"
  27 #include "r300_reg.h"
  28 #include "r300_fs.h"
  29
  30 /*****************************************************************************/
  31 /* The ZTOP state                                                            */
  32 /*****************************************************************************/
  33
  34 static boolean r300_dsa_writes_depth_stencil(struct r300_dsa_state* dsa)
  35 {
  36     /* We are interested only in the cases when a new depth or stencil value
  37      * can be written and changed. */
  38
  39     /* We might optionally check for [Z func: never] and inspect the stencil
  40      * state in a similar fashion, but it's not terribly important. */
  41     return (dsa->z_buffer_control & R300_Z_WRITE_ENABLE) ||
  42            (dsa->stencil_ref_mask & R300_STENCILWRITEMASK_MASK) ||
  43            ((dsa->z_buffer_control & R500_STENCIL_REFMASK_FRONT_BACK) &&
  44             (dsa->stencil_ref_bf & R300_STENCILWRITEMASK_MASK));
  45 }
  46
  47 static boolean r300_dsa_alpha_test_enabled(struct r300_dsa_state* dsa)
  48 {
  49     /* We are interested only in the cases when alpha testing can kill
  50      * a fragment. */
  51     uint32_t af = dsa->alpha_function;
  52
  53     return (af & R300_FG_ALPHA_FUNC_ENABLE) &&
  54            (af & R300_FG_ALPHA_FUNC_ALWAYS) != R300_FG_ALPHA_FUNC_ALWAYS;
  55 }
  56
  57 static void r300_update_ztop(struct r300_context* r300)
  58 {
  59     struct r300_ztop_state* ztop_state =
  60         (struct r300_ztop_state*)r300->ztop_state.state;
  61
  62     /* This is important enough that I felt it warranted a comment.
  63      *
  64      * According to the docs, these are the conditions where ZTOP must be
  65      * disabled:
  66      * 1) Alpha testing enabled
  67      * 2) Texture kill instructions in fragment shader
  68      * 3) Chroma key culling enabled
  69      * 4) W-buffering enabled
  70      *
  71      * The docs claim that for the first three cases, if no ZS writes happen,
  72      * then ZTOP can be used.
  73      *
  74      * (3) will never apply since we do not support chroma-keyed operations.
  75      * (4) will need to be re-examined (and this comment updated) if/when
  76      * Hyper-Z becomes supported.
  77      *
  78      * Additionally, the following conditions require disabled ZTOP:
  79      * 5) Depth writes in fragment shader
  80      * 6) Outstanding occlusion queries
  81      *
  82      * This register causes stalls all the way from SC to CB when changed,
  83      * but it is buffered on-chip so it does not hurt to write it if it has
  84      * not changed.
  85      *
  86      * ~C.
  87      */
  88
  89     /* ZS writes */
  90     if (r300_dsa_writes_depth_stencil(r300->dsa_state.state) &&
  91            (r300_dsa_alpha_test_enabled(r300->dsa_state.state) ||  /* (1) */
  92             r300_fs(r300)->shader->info.uses_kill)) {              /* (2) */
  93         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
  94     } else if (r300_fragment_shader_writes_depth(r300_fs(r300))) { /* (5) */
  95         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
  96     } else if (r300->query_current) {                              /* (6) */
  97         ztop_state->z_buffer_top = R300_ZTOP_DISABLE;
  98     } else {
  99         ztop_state->z_buffer_top = R300_ZTOP_ENABLE;
 100     }
 101
 102     r300->ztop_state.dirty = TRUE;
 103 }
 104
 105 void r300_update_hyperz_state(struct r300_context* r300)
 106 {
 107     r300_update_ztop(r300);
 108 }