iris: Wire up EGL_IMG_context_priority

Add the missing PIPE_CAP_CONTEXT_PRIORITY_MASK and parsing of the context
construction flags.

Testcase: piglit/egl-context-priority

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/gallium/drivers/iris/iris_batch.c

                 struct pipe_debug_callback *dbg,
                 struct iris_batch *all_batches,
                 enum iris_batch_name name,
-                uint8_t engine)
+                uint8_t engine,
+                int priority)
 {
    batch->screen = screen;
    batch->vtbl = vtbl;
    batch->hw_ctx_id = iris_create_hw_context(screen->bufmgr);
    assert(batch->hw_ctx_id);
 
+   iris_hw_context_set_priority(screen->bufmgr, batch->hw_ctx_id, priority);
+
    util_dynarray_init(&batch->exec_fences, ralloc_context(NULL));
    util_dynarray_init(&batch->syncpts, ralloc_context(NULL));
 

src/gallium/drivers/iris/iris_batch.h

                      struct pipe_debug_callback *dbg,
                      struct iris_batch *all_batches,
                      enum iris_batch_name name,
-                     uint8_t ring);
+                     uint8_t ring,
+                     int priority);
 void iris_chain_to_new_batch(struct iris_batch *batch);
 void iris_batch_free(struct iris_batch *batch);
 void iris_batch_maybe_flush(struct iris_batch *batch, unsigned estimate);

src/gallium/drivers/iris/iris_context.c

 #include "iris_context.h"
 #include "iris_resource.h"
 #include "iris_screen.h"
+#include "common/gen_defines.h"
 #include "common/gen_sample_positions.h"
 
 /**
    genX_call(devinfo, init_state, ice);
    genX_call(devinfo, init_blorp, ice);
 
+   int priority = 0;
+   if (flags & PIPE_CONTEXT_HIGH_PRIORITY)
+      priority = GEN_CONTEXT_HIGH_PRIORITY;
+   if (flags & PIPE_CONTEXT_LOW_PRIORITY)
+      priority = GEN_CONTEXT_LOW_PRIORITY;
+
    for (int i = 0; i < IRIS_BATCH_COUNT; i++) {
       iris_init_batch(&ice->batches[i], screen, &ice->vtbl, &ice->dbg,
                       ice->batches, (enum iris_batch_name) i,
-                      I915_EXEC_RENDER);
+                      I915_EXEC_RENDER, priority);
    }
 
    ice->vtbl.init_render_context(screen, &ice->batches[IRIS_BATCH_RENDER],

src/gallium/drivers/iris/iris_screen.c

        */
       return devinfo->has_llc;
 
+   case PIPE_CAP_CONTEXT_PRIORITY_MASK:
+      return PIPE_CONTEXT_PRIORITY_LOW |
+             PIPE_CONTEXT_PRIORITY_MEDIUM |
+             PIPE_CONTEXT_PRIORITY_HIGH;
+
    // XXX: don't hardcode 00:00:02.0 PCI here
    case PIPE_CAP_PCI_GROUP:
       return 0;