linux-kernel - [PATCH] drm/atomic: Handling the case when setting old crtc for plane

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Message-Id: <1525326572-25854-1-git-send-email-satendra.t@samsung.com>
Date:   Thu,  3 May 2018 11:19:32 +0530
From:   Satendra Singh Thakur <satendra.t@...sung.com>
To:     Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Satendra Singh Thakur <satendra.t@...sung.com>,
        Madhur Verma <madhur.verma@...sung.com>,
        Hemanshu Srivastava <hemanshu.s@...sung.com>
Subject: [PATCH] drm/atomic: Handling the case when setting old crtc for
 plane

In the func drm_atomic_set_crtc_for_plane, with the current code,
if crtc of the plane_state and crtc passed as argument to the func
are same, entire func will executed in vein.
It will get state of crtc and clear and set the bits in plane_mask.
All these steps are not required for same old crtc.
Ideally, we should do nothing in this case, this patch handles the same,
and causes the program to return without doing anything in such scenario.

Signed-off-by: Satendra Singh Thakur <satendra.t@...sung.com>
Cc: Madhur Verma <madhur.verma@...sung.com>
Cc: Hemanshu Srivastava <hemanshu.s@...sung.com>
---
 drivers/gpu/drm/drm_atomic.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 7d25c42..5bd3365 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1421,7 +1421,9 @@ drm_atomic_set_crtc_for_plane(struct drm_plane_state *plane_state,
 {
 	struct drm_plane *plane = plane_state->plane;
 	struct drm_crtc_state *crtc_state;
-
+	/* Nothing to do for same crtc*/
+	if (plane_state->crtc == crtc)
+		return 0;
 	if (plane_state->crtc) {
 		crtc_state = drm_atomic_get_crtc_state(plane_state->state,
 						       plane_state->crtc);
-- 
2.7.4