[Mesa-dev] [PATCH v6 4/5] loader/dri3: Enable adaptive_sync via _VARIABLE_REFRESH property

[Michel Dänzer]

On 2018-10-19 6:41 p.m., Nicholas Kazlauskas wrote:
> The DDX driver can be notified of adaptive sync suitability by
> flagging the application's window with the _VARIABLE_REFRESH property.
> 
> This property is set on the first swap the application performs
> when adaptive_sync is set to true in the drirc.
> 
> It's performed here instead of when the loader is initialized for
> two reasons:
> 
> (1) The window's drawable can be missing during loader init.
>     This can be observed during the Unigine Superposition benchmark.
> 
> (2) Adaptive sync will only be enabled closer to when the application
>     actually begins rendering.
> 
> If adaptive_sync is false then the _VARIABLE_REFRESH property
> is deleted on loader init.
> 
> The property is only managed on the glx DRI3 backend for now. This
> should cover most common applications and games on modern hardware.
> 
> Vulkan support can be implemented in a similar manner but would likely
> require splitting the function out into a common helper function.
> 
> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> 
> [...]
>  
> @@ -318,6 +344,7 @@ loader_dri3_drawable_init(xcb_connection_t *conn,
>     xcb_get_geometry_reply_t *reply;
>     xcb_generic_error_t *error;
>     GLint vblank_mode = DRI_CONF_VBLANK_DEF_INTERVAL_1;
> +   unsigned char adaptive_sync;
>     int swap_interval;
>  
>     draw->conn = conn;
> @@ -331,16 +358,28 @@ loader_dri3_drawable_init(xcb_connection_t *conn,
>     draw->have_back = 0;
>     draw->have_fake_front = 0;
>     draw->first_init = true;
> +   draw->adaptive_sync = false;
> +   draw->adaptive_sync_active = false;
>  
>     draw->cur_blit_source = -1;
>     draw->back_format = __DRI_IMAGE_FORMAT_NONE;
>     mtx_init(&draw->mtx, mtx_plain);
>     cnd_init(&draw->event_cnd);
>  
> -   if (draw->ext->config)
> +   if (draw->ext->config) {
>        draw->ext->config->configQueryi(draw->dri_screen,
>                                        "vblank_mode", &vblank_mode);
>  
> +      draw->ext->config->configQueryb(draw->dri_screen,
> +                                      "adaptive_sync",
> +                                      &adaptive_sync);
> +
> +      draw->adaptive_sync = adaptive_sync;
> +   }
> +
> +   if (!adaptive_sync)
> +      set_adaptive_sync_property(conn, draw->drawable, false);

If !draw->ext->config, the local variable adaptive_sync is uninitialized
here. There are multiple ways to solve this, but I think the cleanest
might be to move its definition inside the block, and test
draw->adaptive_sync outside of it.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer