linux-kernel - [PATCH 2/6] drm/mgag200: move format check to drm_plane_helper.atomic_needs

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Message-Id: <20250124-atomic-needs-modeset-v1-2-b0c05c9eda0f@linaro.org>
Date: Fri, 24 Jan 2025 13:14:20 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Dave Airlie <airlied@...hat.com>, Jocelyn Falempe <jfalempe@...hat.com>, 
 Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
 Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
 Kalyan Thota <quic_kalyant@...cinc.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org
Subject: [PATCH 2/6] drm/mgag200: move format check to
 drm_plane_helper.atomic_needs_modeset

For the mgag200 driver if the format of the plane changes, then the PLL
rate needs to be changed. This requires performing a full CRTC modeset.
Current code sets drm_crtc_state.mode_changed from the plane's
atomic_check() callback and then doesn't call drm_atomic_helper_check()
again. It works for the mgag200 driver, but it breaks calling convention
of the drm_atomic_helper_check() function.

Move the check to the new atomic_needs_modeset() callback, removing the
need to set the flag in the atomic_check().

Note: this also checks the check to compare format to the
old_plane_state->fb->format instead of using plane->state->fb->format.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/gpu/drm/mgag200/mgag200_drv.h  |  2 ++
 drivers/gpu/drm/mgag200/mgag200_mode.c | 27 ++++++++++++++++++++-------
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
index 0608fc63e588bb60f1b087d263a34cfd11624b52..42cf0826ed14e0e9e4ed1b7920486bda008a0f99 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.h
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
@@ -354,6 +354,8 @@ extern const uint32_t mgag200_primary_plane_formats[];
 extern const size_t   mgag200_primary_plane_formats_size;
 extern const uint64_t mgag200_primary_plane_fmtmods[];
 
+bool mgag200_primary_plane_helper_atomic_needs_modeset(struct drm_plane *plane,
+						       struct drm_atomic_state *new_state);
 int mgag200_primary_plane_helper_atomic_check(struct drm_plane *plane,
 					      struct drm_atomic_state *new_state);
 void mgag200_primary_plane_helper_atomic_update(struct drm_plane *plane,
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index fb71658c3117b25311f19276d6f4ffdee157ac17..63285b356326a13b465387e5d7ac90ec9fe867cf 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -463,12 +463,31 @@ const uint64_t mgag200_primary_plane_fmtmods[] = {
 	DRM_FORMAT_MOD_INVALID
 };
 
+bool mgag200_primary_plane_helper_atomic_needs_modeset(struct drm_plane *plane,
+						       struct drm_atomic_state *new_state)
+{
+	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
+	struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(new_state, plane);
+	struct drm_framebuffer *new_fb = new_plane_state->fb;
+	struct drm_framebuffer *fb = NULL;
+
+	if (old_plane_state)
+		fb = old_plane_state->fb;
+
+	if (!new_fb)
+		return false;
+
+	if (!fb || (fb->format != new_fb->format))
+		return true;
+
+	return false;
+}
+
 int mgag200_primary_plane_helper_atomic_check(struct drm_plane *plane,
 					      struct drm_atomic_state *new_state)
 {
 	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
 	struct drm_framebuffer *new_fb = new_plane_state->fb;
-	struct drm_framebuffer *fb = NULL;
 	struct drm_crtc *new_crtc = new_plane_state->crtc;
 	struct drm_crtc_state *new_crtc_state = NULL;
 	struct mgag200_crtc_state *new_mgag200_crtc_state;
@@ -486,12 +505,6 @@ int mgag200_primary_plane_helper_atomic_check(struct drm_plane *plane,
 	else if (!new_plane_state->visible)
 		return 0;
 
-	if (plane->state)
-		fb = plane->state->fb;
-
-	if (!fb || (fb->format != new_fb->format))
-		new_crtc_state->mode_changed = true; /* update PLL settings */
-
 	new_mgag200_crtc_state = to_mgag200_crtc_state(new_crtc_state);
 	new_mgag200_crtc_state->format = new_fb->format;
 

-- 
2.39.5