Mesa (master): amd/common/gfx9: workaround DCC corruption more conservatively

[Nicolai Hähnle]

Module: Mesa
Branch: master
Commit: f9ccfda9bc8166f833fdb64adf1eca5b8ee69251
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f9ccfda9bc8166f833fdb64adf1eca5b8ee69251

Author: Nicolai Hähnle <nicolai.haehnle at amd.com>
Date:   Thu Oct 12 11:21:26 2017 +0200

amd/common/gfx9: workaround DCC corruption more conservatively

Fixes KHR-GL45.texture_swizzle.smoke and others on Vega.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102809
Cc: mesa-stable at lists.freedesktop.org
Reviewed-by: Marek Olšák <marek.olsak at amd.com>

---

 src/amd/common/ac_surface.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/amd/common/ac_surface.c b/src/amd/common/ac_surface.c
index f956c14a10..ec37d37698 100644
--- a/src/amd/common/ac_surface.c
+++ b/src/amd/common/ac_surface.c
@@ -927,9 +927,11 @@ static int gfx9_compute_miptree(ADDR_HANDLE addrlib,
 		    in->numSamples == 1) {
 			ADDR2_COMPUTE_DCCINFO_INPUT din = {0};
 			ADDR2_COMPUTE_DCCINFO_OUTPUT dout = {0};
+			ADDR2_META_MIP_INFO meta_mip_info[RADEON_SURF_MAX_LEVELS] = {};
 
 			din.size = sizeof(ADDR2_COMPUTE_DCCINFO_INPUT);
 			dout.size = sizeof(ADDR2_COMPUTE_DCCINFO_OUTPUT);
+			dout.pMipInfo = meta_mip_info;
 
 			din.dccKeyFlags.pipeAligned = 1;
 			din.dccKeyFlags.rbAligned = 1;
@@ -955,21 +957,37 @@ static int gfx9_compute_miptree(ADDR_HANDLE addrlib,
 			surf->dcc_alignment = dout.dccRamBaseAlign;
 			surf->num_dcc_levels = in->numMipLevels;
 
-			/* Disable DCC for the smallest levels. It seems to be
-			 * required for DCC readability between CB and shaders
-			 * when TC L2 isn't flushed. This was guessed.
+			/* Disable DCC for levels that are in the mip tail.
+			 *
+			 * There are two issues that this is intended to
+			 * address:
+			 *
+			 * 1. Multiple mip levels may share a cache line. This
+			 *    can lead to corruption when switching between
+			 *    rendering to different mip levels because the
+			 *    RBs don't maintain coherency.
+			 *
+			 * 2. Texturing with metadata after rendering sometimes
+			 *    fails with corruption, probably for a similar
+			 *    reason.
+			 *
+			 * Working around these issues for all levels in the
+			 * mip tail may be overly conservative, but it's what
+			 * Vulkan does.
 			 *
 			 * Alternative solutions that also work but are worse:
-			 * - Disable DCC.
+			 * - Disable DCC entirely.
 			 * - Flush TC L2 after rendering.
 			 */
-			for (unsigned i = 1; i < in->numMipLevels; i++) {
-				if (mip_info[i].pitch *
-				    mip_info[i].height * surf->bpe < 1024) {
+			for (unsigned i = 0; i < in->numMipLevels; i++) {
+				if (meta_mip_info[i].inMiptail) {
 					surf->num_dcc_levels = i;
 					break;
 				}
 			}
+
+			if (!surf->num_dcc_levels)
+				surf->dcc_size = 0;
 		}
 
 		/* FMASK */