drm/crtc-helper: Add a drm_crtc_helper_atomic_check() helper

Provides a default CRTC state check handler for CRTCs that only have one
primary plane attached.

There are some drivers that duplicate this logic in their helpers, such as
simpledrm and ssd130x. Factor out this common code into a CRTC helper and
make drivers use it.
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20221011165136.469750-5-javierm@redhat.com

drivers/gpu/drm/drm_crtc_helper.c

@@ -421,6 +421,32 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
 }
 EXPORT_SYMBOL(drm_crtc_helper_set_mode);
 
+/**
+ * drm_crtc_helper_atomic_check() - Helper to check CRTC atomic-state
+ * @crtc: CRTC to check
+ * @state: atomic state object
+ *
+ * Provides a default CRTC-state check handler for CRTCs that only have
+ * one primary plane attached to it.
+ *
+ * This is often the case for the CRTC of simple framebuffers. See also
+ * drm_plane_helper_atomic_check() for the respective plane-state check
+ * helper function.
+ *
+ * RETURNS:
+ * Zero on success, or an errno code otherwise.
+ */
+int drm_crtc_helper_atomic_check(struct drm_crtc *crtc, struct drm_atomic_state *state)
+{
+	struct drm_crtc_state *new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+
+	if (!new_crtc_state->enable)
+		return 0;
+
+	return drm_atomic_helper_check_crtc_primary_plane(new_crtc_state);
+}
+EXPORT_SYMBOL(drm_crtc_helper_atomic_check);
+
 static void
 drm_crtc_helper_disable(struct drm_crtc *crtc)
 {

drivers/gpu/drm/drm_plane_helper.c

@@ -298,7 +298,9 @@ EXPORT_SYMBOL(drm_plane_helper_destroy);
  * scale and positioning are not expected to change since the plane is always
  * a fullscreen scanout buffer.
  *
- * This is often the case for the primary plane of simple framebuffers.
+ * This is often the case for the primary plane of simple framebuffers. See
+ * also drm_crtc_helper_atomic_check() for the respective CRTC-state check
+ * helper function.
  *
  * RETURNS:
  * Zero on success, or an errno code otherwise.

drivers/gpu/drm/solomon/ssd130x.c

@@ -20,6 +20,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_crtc_helper.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_fb_helper.h>
@@ -645,17 +646,6 @@ static enum drm_mode_status ssd130x_crtc_helper_mode_valid(struct drm_crtc *crtc
 	return MODE_OK;
 }
 
-static int ssd130x_crtc_helper_atomic_check(struct drm_crtc *crtc,
-					    struct drm_atomic_state *new_state)
-{
-	struct drm_crtc_state *new_crtc_state = drm_atomic_get_new_crtc_state(new_state, crtc);
-
-	if (!new_crtc_state->enable)
-		return 0;
-
-	return drm_atomic_helper_check_crtc_primary_plane(new_crtc_state);
-}
-
 /*
  * The CRTC is always enabled. Screen updates are performed by
  * the primary plane's atomic_update function. Disabling clears
@@ -663,7 +653,7 @@ static int ssd130x_crtc_helper_atomic_check(struct drm_crtc *crtc,
  */
 static const struct drm_crtc_helper_funcs ssd130x_crtc_helper_funcs = {
 	.mode_valid = ssd130x_crtc_helper_mode_valid,
-	.atomic_check = ssd130x_crtc_helper_atomic_check,
+	.atomic_check = drm_crtc_helper_atomic_check,
 };
 
 static void ssd130x_crtc_reset(struct drm_crtc *crtc)

drivers/gpu/drm/tiny/simpledrm.c

@@ -11,6 +11,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_connector.h>
+#include <drm/drm_crtc_helper.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
@@ -545,17 +546,6 @@ static enum drm_mode_status simpledrm_crtc_helper_mode_valid(struct drm_crtc *cr
 	return drm_crtc_helper_mode_valid_fixed(crtc, mode, &sdev->mode);
 }
 
-static int simpledrm_crtc_helper_atomic_check(struct drm_crtc *crtc,
-					      struct drm_atomic_state *new_state)
-{
-	struct drm_crtc_state *new_crtc_state = drm_atomic_get_new_crtc_state(new_state, crtc);
-
-	if (!new_crtc_state->enable)
-		return 0;
-
-	return drm_atomic_helper_check_crtc_primary_plane(new_crtc_state);
-}
-
 /*
  * The CRTC is always enabled. Screen updates are performed by
  * the primary plane's atomic_update function. Disabling clears
@@ -563,7 +553,7 @@ static int simpledrm_crtc_helper_atomic_check(struct drm_crtc *crtc,
  */
 static const struct drm_crtc_helper_funcs simpledrm_crtc_helper_funcs = {
 	.mode_valid = simpledrm_crtc_helper_mode_valid,
-	.atomic_check = simpledrm_crtc_helper_atomic_check,
+	.atomic_check = drm_crtc_helper_atomic_check,
 };
 
 static const struct drm_crtc_funcs simpledrm_crtc_funcs = {

include/drm/drm_crtc_helper.h

@@ -50,6 +50,8 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
 			      struct drm_display_mode *mode,
 			      int x, int y,
 			      struct drm_framebuffer *old_fb);
+int drm_crtc_helper_atomic_check(struct drm_crtc *crtc,
+				 struct drm_atomic_state *state);
 bool drm_helper_crtc_in_use(struct drm_crtc *crtc);
 bool drm_helper_encoder_in_use(struct drm_encoder *encoder);