Mesa (staging/20.2): st/pbo: fix pbo uploads without PIPE_CAP_TGSI_VS_LAYER_VIEWPORT

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Module: Mesa
Branch: staging/20.2
Commit: 5ac08afcfc7a3bef254c4ef608f37d24b8aa07b6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=5ac08afcfc7a3bef254c4ef608f37d24b8aa07b6

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Fri Dec 11 19:00:23 2020 -0500

st/pbo: fix pbo uploads without PIPE_CAP_TGSI_VS_LAYER_VIEWPORT

the code here tries to be too smart and only use a geometry shader if there's
actually multiple layers being uploaded, but the fragment shader also unconditionally
reads gl_Layer as long as the pipe cap for gs is set, which means that
in the case when the gs is dynamically disabled due to uploading a
single-layer surface, the fs has no input to read for gl_Layer and everything breaks

always using a gs isn't ideal, but it's considerably more work to manage multiple
fs variants based on layer usage

Fixes: c99f2fe70ec ("st/mesa: implement PBO upload for multiple layers")
Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8067>
(cherry picked from commit 614c77772ac2f48955537efcfefaf0609d6c03e5)

---

 .pick_status.json               | 2 +-
 src/mesa/state_tracker/st_pbo.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index c2b359156e8..b8de47a28fa 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -157,7 +157,7 @@
         "description": "st/pbo: fix pbo uploads without PIPE_CAP_TGSI_VS_LAYER_VIEWPORT",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": "c99f2fe70ec6a9273786d123fa4ac9924b5911b2"
     },
diff --git a/src/mesa/state_tracker/st_pbo.c b/src/mesa/state_tracker/st_pbo.c
index ee5ee2df598..f6abffd7454 100644
--- a/src/mesa/state_tracker/st_pbo.c
+++ b/src/mesa/state_tracker/st_pbo.c
@@ -202,7 +202,7 @@ st_pbo_draw(struct st_context *st, const struct st_pbo_addresses *addr,
          return false;
    }
 
-   if (addr->depth != 1 && st->pbo.use_gs && !st->pbo.gs) {
+   if (st->pbo.use_gs && !st->pbo.gs) {
       st->pbo.gs = st_pbo_create_gs(st);
       if (!st->pbo.gs)
          return false;