Mesa (master): freedreno/a6xx: document LRZ flag buffer
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Fri May 29 01:08:50 UTC 2020
Module: Mesa
Branch: master
Commit: 6f391262003e2d58395dd17d2cf1e1a6807f7a0a
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=6f391262003e2d58395dd17d2cf1e1a6807f7a0a
Author: Rob Clark <robdclark at chromium.org>
Date: Wed May 27 13:50:05 2020 -0700
freedreno/a6xx: document LRZ flag buffer
Doesn't seem to be a big win, although I could still be missing
something in my implementation. But might as well add the
documentation.
Signed-off-by: Rob Clark <robdclark at chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5217>
---
src/freedreno/registers/a6xx.xml | 33 ++++++++++++++++++++++++++-
src/gallium/drivers/freedreno/a6xx/fd6_gmem.c | 2 +-
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/src/freedreno/registers/a6xx.xml b/src/freedreno/registers/a6xx.xml
index a718b24149f..72c0c384fca 100644
--- a/src/freedreno/registers/a6xx.xml
+++ b/src/freedreno/registers/a6xx.xml
@@ -1973,7 +1973,7 @@ to upconvert to 32b float internally?
<bitfield name="LRZ_WRITE" pos="1" type="boolean"/>
<doc>update MAX instead of MIN value, ie. GL_GREATER/GL_GEQUAL</doc>
<bitfield name="GREATER" pos="2" type="boolean"/>
- <bitfield name="UNK3" pos="3" type="boolean"/>
+ <bitfield name="FC_ENABLE" pos="3" type="boolean"/>
<!-- set when depth-test + depth-write enabled -->
<bitfield name="Z_TEST_ENABLE" pos="4" type="boolean"/>
</reg32>
@@ -1988,6 +1988,37 @@ to upconvert to 32b float internally?
<bitfield name="PITCH" low="0" high="10" shr="5" type="uint"/>
<bitfield name="ARRAY_PITCH" low="11" high="21" shr="5" type="uint"/> <!-- ??? -->
</reg32>
+
+ <!--
+ The LRZ "fast clear" buffer is initialized to zero's by blob, and
+ read/written when GRAS_LRZ_CNTL.FC_ENABLE (b3) is set. It appears
+ to store 1b/block. It appears that '0' means block has original
+ depth clear value, and '1' means that the corresponding block in
+ LRZ has been modified. Ignoring alignment/padding, the size is
+ given by the formula:
+
+ // calculate LRZ size from depth size:
+ if (nr_samples == 4) {
+ width *= 2;
+ height *= 2;
+ } else if (nr_samples == 2) {
+ height *= 2;
+ }
+
+ lrz_width = div_round_up(width, 8);
+ lrz_heigh = div_round_up(height, 8);
+
+ // calculate # of blocks:
+ nblocksx = div_round_up(lrz_width, 16);
+ nblocksy = div_round_up(lrz_height, 4);
+
+ // fast-clear buffer is 1bit/block:
+ fc_sz = div_round_up(nblocksx * nblocksy, 8);
+
+ In practice the blob seems to switch off FC_ENABLE once the size
+ increases beyond 1 page. Not sure if that is an actual limit or
+ not.
+ -->
<reg32 offset="0x8106" name="GRAS_LRZ_FAST_CLEAR_BUFFER_BASE_LO"/>
<reg32 offset="0x8107" name="GRAS_LRZ_FAST_CLEAR_BUFFER_BASE_HI"/>
<reg32 offset="0x8106" name="GRAS_LRZ_FAST_CLEAR_BUFFER_BASE" type="waddress"/>
diff --git a/src/gallium/drivers/freedreno/a6xx/fd6_gmem.c b/src/gallium/drivers/freedreno/a6xx/fd6_gmem.c
index b71c77ddc6c..790215dbc0b 100644
--- a/src/gallium/drivers/freedreno/a6xx/fd6_gmem.c
+++ b/src/gallium/drivers/freedreno/a6xx/fd6_gmem.c
@@ -1381,7 +1381,7 @@ fd6_emit_tile_fini(struct fd_batch *batch)
fd6_emit_ib(batch->gmem, batch->epilogue);
OUT_PKT4(ring, REG_A6XX_GRAS_LRZ_CNTL, 1);
- OUT_RING(ring, A6XX_GRAS_LRZ_CNTL_ENABLE | A6XX_GRAS_LRZ_CNTL_UNK3);
+ OUT_RING(ring, A6XX_GRAS_LRZ_CNTL_ENABLE | A6XX_GRAS_LRZ_CNTL_FC_ENABLE);
fd6_emit_lrz_flush(ring);
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