[PATCH 6.1 151/223] drm/amd/display: add a NULL pointer check

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Sung-huai Wang <danny.wang@xxxxxxx>

commit 0f48a4b83610cb0e4e0bc487800ab69f51b4aca6 upstream.

[Why & How]

We have to check if stream is properly initialized before calling
find_matching_pll(), otherwise we might end up trying to deferecence a
NULL pointer.

Cc: stable@xxxxxxxxxxxxxxx # 6.1+
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Acked-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
Signed-off-by: Sung-huai Wang <danny.wang@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/dc/dce112/dce112_resource.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/dce112/dce112_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dce112/dce112_resource.c
@@ -970,10 +970,12 @@ enum dc_status resource_map_phy_clock_re
 		|| dc_is_virtual_signal(pipe_ctx->stream->signal))
 		pipe_ctx->clock_source =
 				dc->res_pool->dp_clock_source;
-	else
-		pipe_ctx->clock_source = find_matching_pll(
-			&context->res_ctx, dc->res_pool,
-			stream);
+	else {
+		if (stream && stream->link && stream->link->link_enc)
+			pipe_ctx->clock_source = find_matching_pll(
+				&context->res_ctx, dc->res_pool,
+				stream);
+	}
 
 	if (pipe_ctx->clock_source == NULL)
 		return DC_NO_CLOCK_SOURCE_RESOURCE;