drm/amd/display: Check otg_master pointer before use it

Coverity highlighted that the parameter otg_master is referenced before
the if condition that validates it, which means that the code might have
some attempt to access a null pointer. This commit addresses this issue
by moving the pointer verification to the beginning of the function and
initializing all the values right after it.
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -2077,15 +2077,23 @@ int resource_get_odm_slice_index(const struct pipe_ctx *pipe_ctx)
 int resource_get_odm_slice_dst_width(struct pipe_ctx *otg_master,
 		bool is_last_segment)
 {
-	const struct dc_crtc_timing *timing = &otg_master->stream->timing;
-	int count = resource_get_odm_slice_count(otg_master);
-	int h_active = timing->h_addressable +
-			timing->h_border_left +
-			timing->h_border_right;
-	int width = h_active / count;
+	const struct dc_crtc_timing *timing;
+	int count;
+	int h_active;
+	int width;
 	bool two_pixel_alignment_required = false;
 
-	if (otg_master && otg_master->stream_res.tg && otg_master->stream)
+	if (!otg_master || !otg_master->stream)
+		return 0;
+
+	timing = &otg_master->stream->timing;
+	count = resource_get_odm_slice_count(otg_master);
+	h_active = timing->h_addressable +
+		   timing->h_border_left +
+		   timing->h_border_right;
+	width = h_active / count;
+
+	if (otg_master->stream_res.tg && otg_master->stream)
 		two_pixel_alignment_required = otg_master->stream_res.tg->funcs->is_two_pixels_per_container(timing);
 
 	if ((width % 2) && two_pixel_alignment_required)