Mesa (gles3): r300g: add a workaround for the AA colorbuffer addressing bug on R500

[Ian Romanick]

Module: Mesa
Branch: gles3
Commit: 4a1af434e6bfc80fceab2a472e7a79de59aca823
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4a1af434e6bfc80fceab2a472e7a79de59aca823

Author: Marek Olšák <maraeo at gmail.com>
Date:   Sun Jan 20 18:09:58 2013 +0100

r300g: add a workaround for the AA colorbuffer addressing bug on R500

---

 src/gallium/drivers/r300/r300_state.c        |   18 +++++++++------
 src/gallium/drivers/r300/r300_texture_desc.c |   31 ++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/src/gallium/drivers/r300/r300_state.c b/src/gallium/drivers/r300/r300_state.c
index e5d9beb..fd02f82 100644
--- a/src/gallium/drivers/r300/r300_state.c
+++ b/src/gallium/drivers/r300/r300_state.c
@@ -839,14 +839,18 @@ static unsigned r300_get_num_samples(struct r300_context *r300)
 {
     struct pipe_framebuffer_state* fb =
             (struct pipe_framebuffer_state*)r300->fb_state.state;
-    unsigned num_samples;
+    unsigned i, num_samples;
 
-    if (fb->nr_cbufs)
-        num_samples = fb->cbufs[0]->texture->nr_samples;
-    else if (fb->zsbuf)
-        num_samples = fb->zsbuf->texture->nr_samples;
-    else
-        num_samples = 1;
+    if (!fb->nr_cbufs && !fb->zsbuf)
+        return 1;
+
+    num_samples = 6;
+
+    for (i = 0; i < fb->nr_cbufs; i++)
+        num_samples = MIN2(num_samples, fb->cbufs[i]->texture->nr_samples);
+
+    if (fb->zsbuf)
+        num_samples = MIN2(num_samples, fb->zsbuf->texture->nr_samples);
 
     if (!num_samples)
         num_samples = 1;
diff --git a/src/gallium/drivers/r300/r300_texture_desc.c b/src/gallium/drivers/r300/r300_texture_desc.c
index c5636ca..6d64528 100644
--- a/src/gallium/drivers/r300/r300_texture_desc.c
+++ b/src/gallium/drivers/r300/r300_texture_desc.c
@@ -542,6 +542,37 @@ void r300_texture_desc_init(struct r300_screen *rscreen,
     tex->tex.height0 = base->height0;
     tex->tex.depth0 = base->depth0;
 
+    /* There is a CB memory addressing hardware bug that limits the width
+     * of the MSAA buffer in some cases in R520. In order to get around it,
+     * the following code lowers the sample count depending on the format and
+     * the width.
+     *
+     * The only catch is that all MSAA colorbuffers and a zbuffer which are
+     * supposed to be used together should always be bound together. Only
+     * then the correct minimum sample count of all bound buffers is used
+     * for rendering. */
+    if (rscreen->caps.is_r500) {
+        /* FP16 6x MSAA buffers are limited to a width of 1360 pixels. */
+        if (tex->b.b.format == PIPE_FORMAT_R16G16B16A16_FLOAT &&
+            tex->b.b.nr_samples == 6 && tex->b.b.width0 > 1360) {
+            tex->b.b.nr_samples = 4;
+        }
+
+        /* FP16 4x MSAA buffers are limited to a width of 2048 pixels. */
+        if (tex->b.b.format == PIPE_FORMAT_R16G16B16A16_FLOAT &&
+            tex->b.b.nr_samples == 4 && tex->b.b.width0 > 2048) {
+            tex->b.b.nr_samples = 2;
+        }
+    }
+
+    /* 32-bit 6x MSAA buffers are limited to a width of 2720 pixels.
+     * This applies to all R300-R500 cards. */
+    if (util_format_get_blocksizebits(tex->b.b.format) == 32 &&
+        !util_format_is_depth_or_stencil(tex->b.b.format) &&
+        tex->b.b.nr_samples == 6 && tex->b.b.width0 > 2720) {
+        tex->b.b.nr_samples = 4;
+    }
+
     r300_setup_flags(tex);
 
     /* Align a 3D NPOT texture to POT. */