freedreno: add env var to override GMEM size

Sometimes it is useful to force a smaller size while debugging.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6461>

src/gallium/drivers/freedreno/freedreno_screen.c

@@ -879,7 +879,7 @@ fd_screen_create(struct fd_device *dev, struct renderonly *ro)
 		DBG("could not get GMEM size");
 		goto fail;
 	}
-	screen->gmemsize_bytes = val;
+	screen->gmemsize_bytes = env_var_as_unsigned("FD_MESA_GMEM", val);
 
 	if (fd_device_version(dev) >= FD_VERSION_GMEM_BASE) {
 		fd_pipe_get_param(screen->pipe, FD_GMEM_BASE, &screen->gmem_base);

src/gallium/drivers/freedreno/freedreno_screen.h

@@ -32,6 +32,7 @@
 #include "perfcntrs/freedreno_perfcntr.h"
 
 #include "pipe/p_screen.h"
+#include "util/debug.h"
 #include "util/u_memory.h"
 #include "util/slab.h"
 #include "util/simple_mtx.h"