[PATCH v1 14/16] drm/panel: call prepare/enable only once

[Sam Ravnborg]

Many panel drivers duplicate logic to prevent prepare to be called
for a panel that is already prepared.
Likewise for enable.

Implement this logic in drm_panel so the individual drivers
no longer needs this.
A panel is considered prepared/enabled only if the prepare/enable call
succeeds.
For disable/unprepare it is unconditionally considered
disabled/unprepared.

This allows calls to prepare/enable again, even if there were
some issue disabling a regulator or similar during disable/unprepare.

Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <maxime.ripard at bootlin.com>
Cc: Sean Paul <sean at poorly.run>
Cc: Thierry Reding <thierry.reding at gmail.com>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
---
 drivers/gpu/drm/drm_panel.c | 66 ++++++++++++++++++++++++++++++-------
 include/drm/drm_panel.h     | 21 ++++++++++++
 2 files changed, 75 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index da19d5b4a2f4..0853764040de 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -66,10 +66,21 @@ EXPORT_SYMBOL(drm_panel_init);
  */
 int drm_panel_prepare(struct drm_panel *panel)
 {
-	if (panel && panel->funcs && panel->funcs->prepare)
-		return panel->funcs->prepare(panel);
+	int ret = -ENOSYS;
 
-	return panel ? -ENOSYS : -EINVAL;
+	if (!panel)
+		return -EINVAL;
+
+	if (panel->prepared)
+		return 0;
+
+	if (panel->funcs && panel->funcs->prepare)
+		ret = panel->funcs->prepare(panel);
+
+	if (ret >= 0)
+		panel->prepared = true;
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_panel_prepare);
 
@@ -85,10 +96,21 @@ EXPORT_SYMBOL(drm_panel_prepare);
  */
 int drm_panel_enable(struct drm_panel *panel)
 {
-	if (panel && panel->funcs && panel->funcs->enable)
-		return panel->funcs->enable(panel);
+	int ret = -ENOSYS;
 
-	return panel ? -ENOSYS : -EINVAL;
+	if (!panel)
+		return -EINVAL;
+
+	if (panel->enabled)
+		return 0;
+
+	if (panel->funcs && panel->funcs->enable)
+		ret = panel->funcs->enable(panel);
+
+	if (ret >= 0)
+		panel->enabled = true;
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_panel_enable);
 
@@ -104,10 +126,20 @@ EXPORT_SYMBOL(drm_panel_enable);
  */
 int drm_panel_disable(struct drm_panel *panel)
 {
-	if (panel && panel->funcs && panel->funcs->disable)
-		return panel->funcs->disable(panel);
+	int ret = -ENOSYS;
 
-	return panel ? -ENOSYS : -EINVAL;
+	if (!panel)
+		return -EINVAL;
+
+	if (!panel->enabled)
+		return 0;
+
+	if (panel->funcs && panel->funcs->disable)
+		ret = panel->funcs->disable(panel);
+
+	panel->enabled = false;
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_panel_disable);
 
@@ -124,10 +156,20 @@ EXPORT_SYMBOL(drm_panel_disable);
  */
 int drm_panel_unprepare(struct drm_panel *panel)
 {
-	if (panel && panel->funcs && panel->funcs->unprepare)
-		return panel->funcs->unprepare(panel);
+	int ret = -ENOSYS;
 
-	return panel ? -ENOSYS : -EINVAL;
+	if (!panel)
+		return -EINVAL;
+
+	if (!panel->prepared)
+		return 0;
+
+	if (panel->funcs && panel->funcs->unprepare)
+		ret = panel->funcs->unprepare(panel);
+
+	panel->prepared = false;
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_panel_unprepare);
 
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 624bd15ecfab..7493500fc9bd 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -65,6 +65,9 @@ struct drm_panel_funcs {
 	 * @prepare:
 	 *
 	 * Turn on panel and perform set up.
+	 * When the panel is successfully prepared the prepare() function
+	 * will not be called again until the panel has been unprepared.
+	 *
 	 */
 	int (*prepare)(struct drm_panel *panel);
 
@@ -72,6 +75,8 @@ struct drm_panel_funcs {
 	 * @enable:
 	 *
 	 * Enable panel (turn on back light, etc.).
+	 * When the panel is successfully enabled the enable() function
+	 * will not be called again until the panel has been disabled.
 	 */
 	int (*enable)(struct drm_panel *panel);
 
@@ -79,6 +84,7 @@ struct drm_panel_funcs {
 	 * @disable:
 	 *
 	 * Disable panel (turn off back light, etc.).
+	 * If the panel is already disabled the disable() function is not called.
 	 */
 	int (*disable)(struct drm_panel *panel);
 
@@ -86,6 +92,7 @@ struct drm_panel_funcs {
 	 * @unprepare:
 	 *
 	 * Turn off panel.
+	 * If the panel is already unprepared the unprepare() function is not called.
 	 */
 	int (*unprepare)(struct drm_panel *panel);
 
@@ -145,6 +152,20 @@ struct drm_panel {
 	 * Panel entry in registry.
 	 */
 	struct list_head list;
+
+	/**
+	 * @prepared:
+	 *
+	 * Set to true when the panel is successfully prepared.
+	 */
+	bool prepared;
+
+	/**
+	 * @enabled:
+	 *
+	 * Set to true when the panel is successfully enabled.
+	 */
+	bool enabled;
 };
 
 void drm_panel_init(struct drm_panel *panel);
-- 
2.20.1