vc4: Add a debug flag for flushing after every draw.

It was useful on i965, but it's even more useful for debugging tiled
renderers.

src/gallium/drivers/vc4/vc4_draw.c

@@ -193,6 +193,9 @@ vc4_draw_vbo(struct pipe_context *pctx, const struct pipe_draw_info *info)
         vc4->resolve |= PIPE_CLEAR_COLOR0;
 
         vc4->shader_rec_count++;
+
+        if (vc4_debug & VC4_DEBUG_ALWAYS_FLUSH)
+                vc4_flush(pctx);
 }
 
 static uint32_t

src/gallium/drivers/vc4/vc4_screen.c

@@ -50,6 +50,8 @@ static const struct debug_named_value debug_options[] = {
           "Print during performance-related events" },
         { "norast",   VC4_DEBUG_NORAST,
           "Skip actual hardware execution of commands" },
+        { "always_flush", VC4_DEBUG_ALWAYS_FLUSH,
+          "Flush after each draw call" },
         { NULL }
 };
 

src/gallium/drivers/vc4/vc4_screen.h

@@ -36,6 +36,7 @@ struct vc4_bo;
 #define VC4_DEBUG_SHADERDB  0x0010
 #define VC4_DEBUG_PERF      0x0020
 #define VC4_DEBUG_NORAST    0x0040
+#define VC4_DEBUG_ALWAYS_FLUSH 0x0080
 
 #define VC4_MAX_MIP_LEVELS 12
 #define VC4_MAX_TEXTURE_SAMPLERS 16