[Mesa-dev] [PATCH 2/2] swr: Report format max_samples=1 to maintain support for "fake" msaa.

[Kyriazis, George]

Discussed with Bruce.

Reviewed-By: George Kyriazis <george.kyriazis at intel.com<mailto:george.kyriazis at intel.com>>

On Aug 31, 2017, at 11:09 PM, Brian Paul <brianp at vmware.com<mailto:brianp at vmware.com>> wrote:

I'm not familiar with this driver so I'll give this an

Acked-by: Brian Paul <brianp at vmware.com<mailto:brianp at vmware.com>>

Roland gave me his R-b for the state tracker patch off-list.

I'll commit that and you can take care of this one.  Feel free to close the bug then.

-Brian


On 08/25/2017 01:59 PM, Bruce Cherniak wrote:
Accompanying patch "st/mesa: only try to create 1x msaa surfaces for
'fake' msaa" requires driver to report max_samples=1 to enable "fake"
msaa. Previously, 0 and 1 were treated equivalently in st_init_extensions()
and either could enable "fake" msaa.

This patch raises the swr default msaa_max_count from 0 to 1, so that
swr_is_format_supported will report max_samples=1.

Real msaa can still be enabled by exporting SWR_MSAA_MAX_COUNT with a
pow2 value between 2 and 16.

This patch is necessary to prevent an OpenSWR regression resulting from
the st/mesa patch.

Bugzilla: https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D102038&d=DwIBAg&c=uilaK90D4TOVoH58JNXRgQ&r=Ie7_encNUsqxbSRbqbNgofw0ITcfE8JKfaUjIQhncGA&m=qdD02tm0IRZ3cDM-14sDyg5PjXgN7HpvqxwdIKPKG_0&s=Lfh53G7s15bwea6KD_n-r5t38aWcMLmz8Dp-k0TfKbA&e=
---
 src/gallium/drivers/swr/swr_screen.cpp | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/gallium/drivers/swr/swr_screen.cpp b/src/gallium/drivers/swr/swr_screen.cpp
index 3287bc6fee..cc8d9955b8 100644
--- a/src/gallium/drivers/swr/swr_screen.cpp
+++ b/src/gallium/drivers/swr/swr_screen.cpp
@@ -255,13 +255,13 @@ swr_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return 1;

    /* MSAA support
-    * If user has explicitly set max_sample_count = 0 (via SWR_MSAA_MAX_COUNT)
-    * then disable all MSAA support and go back to old caps. */
+    * If user has explicitly set max_sample_count = 1 (via SWR_MSAA_MAX_COUNT)
+    * then disable all MSAA support and go back to old (FAKE_SW_MSAA) caps. */
    case PIPE_CAP_TEXTURE_MULTISAMPLE:
    case PIPE_CAP_MULTISAMPLE_Z_RESOLVE:
-      return swr_screen(screen)->msaa_max_count ? 1 : 0;
+      return (swr_screen(screen)->msaa_max_count > 1) ? 1 : 0;
    case PIPE_CAP_FAKE_SW_MSAA:
-      return swr_screen(screen)->msaa_max_count ? 0 : 1;
+      return (swr_screen(screen)->msaa_max_count > 1) ? 0 : 1;

       /* unsupported features */
    case PIPE_CAP_ANISOTROPIC_FILTER:
@@ -1079,22 +1079,22 @@ swr_validate_env_options(struct swr_screen *screen)
       screen->client_copy_limit = client_copy_limit;

    /* XXX msaa under development, disable by default for now */
-   screen->msaa_max_count = 0; /* was SWR_MAX_NUM_MULTISAMPLES; */
+   screen->msaa_max_count = 1; /* was SWR_MAX_NUM_MULTISAMPLES; */

    /* validate env override values, within range and power of 2 */
-   int msaa_max_count = debug_get_num_option("SWR_MSAA_MAX_COUNT", 0);
-   if (msaa_max_count) {
-      if ((msaa_max_count < 0) || (msaa_max_count > SWR_MAX_NUM_MULTISAMPLES)
+   int msaa_max_count = debug_get_num_option("SWR_MSAA_MAX_COUNT", 1);
+   if (msaa_max_count != 1) {
+      if ((msaa_max_count < 1) || (msaa_max_count > SWR_MAX_NUM_MULTISAMPLES)
             || !util_is_power_of_two(msaa_max_count)) {
          fprintf(stderr, "SWR_MSAA_MAX_COUNT invalid: %d\n", msaa_max_count);
          fprintf(stderr, "must be power of 2 between 1 and %d" \
-                         " (or 0 to disable msaa)\n",
+                         " (or 1 to disable msaa)\n",
                SWR_MAX_NUM_MULTISAMPLES);
-         msaa_max_count = 0;
+         msaa_max_count = 1;
       }

       fprintf(stderr, "SWR_MSAA_MAX_COUNT: %d\n", msaa_max_count);
-      if (!msaa_max_count)
+      if (msaa_max_count == 1)
          fprintf(stderr, "(msaa disabled)\n");

       screen->msaa_max_count = msaa_max_count;


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