[RFC PATCH 1/2] drm: Introduce drm_panel_prepare_for_mode callback

[Val Packett <val@packett.cool>]

Modern OLED panels often need to vary their prepare commands based on the
mode being set (resolution and refresh rate). Introduce a new variant of
the drm_panel_prepare callback that passes the chosen mode as an argument
to allow for this.

Signed-off-by: Val Packett <val@packett.cool>
---
 drivers/gpu/drm/bridge/panel.c |  8 ++++++--
 drivers/gpu/drm/drm_panel.c    | 15 +++++++++++++--
 include/drm/drm_panel.h        | 12 ++++++++++++
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 184a8b7049a7..58c9d9c44363 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -116,7 +116,7 @@ static void panel_bridge_atomic_pre_enable(struct drm_bridge *bridge,
 	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	struct drm_encoder *encoder = bridge->encoder;
 	struct drm_crtc *crtc;
-	struct drm_crtc_state *old_crtc_state;
+	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
 
 	crtc = drm_atomic_get_new_crtc_for_encoder(atomic_state, encoder);
 	if (!crtc)
@@ -126,7 +126,11 @@ static void panel_bridge_atomic_pre_enable(struct drm_bridge *bridge,
 	if (old_crtc_state && old_crtc_state->self_refresh_active)
 		return;
 
-	drm_panel_prepare(panel_bridge->panel);
+	new_crtc_state = drm_atomic_get_new_crtc_state(atomic_state, crtc);
+	if (!new_crtc_state)
+		return;
+
+	drm_panel_prepare_for_mode(panel_bridge->panel, &new_crtc_state->mode);
 }
 
 static void panel_bridge_atomic_enable(struct drm_bridge *bridge,
diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index d1e6598ea3bc..cc313f778253 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -112,6 +112,13 @@ EXPORT_SYMBOL(drm_panel_remove);
  * drm_panel_disable() afterwards.
  */
 void drm_panel_prepare(struct drm_panel *panel)
+{
+	drm_panel_prepare_for_mode(panel, NULL);
+}
+EXPORT_SYMBOL(drm_panel_prepare);
+
+void drm_panel_prepare_for_mode(struct drm_panel *panel,
+                                struct drm_display_mode *mode)
 {
 	struct drm_panel_follower *follower;
 	int ret;
@@ -126,7 +133,11 @@ void drm_panel_prepare(struct drm_panel *panel)
 
 	mutex_lock(&panel->follower_lock);
 
-	if (panel->funcs && panel->funcs->prepare) {
+	if (panel->funcs && panel->funcs->prepare_for_mode && mode) {
+		ret = panel->funcs->prepare_for_mode(panel, mode);
+		if (ret < 0)
+			goto exit;
+	} else if (panel->funcs && panel->funcs->prepare) {
 		ret = panel->funcs->prepare(panel);
 		if (ret < 0)
 			goto exit;
@@ -146,7 +157,7 @@ void drm_panel_prepare(struct drm_panel *panel)
 exit:
 	mutex_unlock(&panel->follower_lock);
 }
-EXPORT_SYMBOL(drm_panel_prepare);
+EXPORT_SYMBOL(drm_panel_prepare_for_mode);
 
 /**
  * drm_panel_unprepare - power off a panel
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 2407bfa60236..0c2e5232ab20 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -80,6 +80,16 @@ struct drm_panel_funcs {
 	 */
 	int (*prepare)(struct drm_panel *panel);
 
+	/**
+	 * @prepare_for_mode:
+	 *
+	 * Turn on panel and perform set up, with awareness of the mode being set.
+	 *
+	 * This function is optional.
+	 */
+	int (*prepare_for_mode)(struct drm_panel *panel,
+	                        struct drm_display_mode *mode);
+
 	/**
 	 * @enable:
 	 *
@@ -331,6 +341,8 @@ void drm_panel_add(struct drm_panel *panel);
 void drm_panel_remove(struct drm_panel *panel);
 
 void drm_panel_prepare(struct drm_panel *panel);
+void drm_panel_prepare_for_mode(struct drm_panel *panel,
+                                struct drm_display_mode *mode);
 void drm_panel_unprepare(struct drm_panel *panel);
 
 void drm_panel_enable(struct drm_panel *panel);
-- 
2.53.0