[PATCH] drm/amd/display: Fix BUG_ON during CRTC atomic check update

[sunpeng.li at amd.com]

From: "Leo (Sunpeng) Li" <sunpeng.li at amd.com>

For cases where the CRTC is inactive (DPMS off), where a modeset is not
required, yet the CRTC is still in the atomic state, we should not
attempt to update anything on it.

Previously, we were relying on the modereset_required() helper to check
the above condition. However, the function returns false immediatly if
a modeset is not required, ignoring the CRTC's enable/active state
flags. The correct way to filter is by looking at these flags instead.

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com>
Reviewed-by: Harry Wentland <harry.wentland at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 72f9a46..16d0bf7 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4823,15 +4823,16 @@ static int dm_update_crtcs_state(struct amdgpu_display_manager *dm,
 		 * We want to do dc stream updates that do not require a
 		 * full modeset below.
 		 */
-		if (!enable || !aconnector || modereset_required(new_crtc_state))
+		if (!(enable && aconnector && new_crtc_state->enable &&
+		      new_crtc_state->active))
 			continue;
 		/*
 		 * Given above conditions, the dc state cannot be NULL because:
-		 * 1. We're attempting to enable a CRTC. Which has a...
-		 * 2. Valid connector attached, and
-		 * 3. User does not want to reset it (disable or mark inactive,
-		 *    which can happen on a CRTC that's already disabled).
-		 * => It currently exists.
+		 * 1. We're in the process of enabling CRTCs (just been added
+		 *    to the dc context, or already is on the context)
+		 * 2. Has a valid connector attached, and
+		 * 3. Is currently active and enabled.
+		 * => The dc stream state currently exists.
 		 */
 		BUG_ON(dm_new_crtc_state->stream == NULL);
 
-- 
2.7.4