[PATCH 1/2] drm/panel: Allow powering on panel follower after panel is enabled

[Pin-Yen Lin]

Some touch controllers have to be powered on after the panel's backlight
is enabled. To support these controllers, introduce after_panel_enabled
flag to the panel follower and power on the device after the panel and
its backlight are enabled.

Signed-off-by: Pin-Yen Lin <treapk...@google.com>
---

 drivers/gpu/drm/drm_panel.c | 47 +++++++++++++++++++++++++++++++++----
 include/drm/drm_panel.h     |  8 +++++++
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 650de4da08537..58125f8418f37 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -133,6 +133,9 @@ void drm_panel_prepare(struct drm_panel *panel)
        panel->prepared = true;
 
        list_for_each_entry(follower, &panel->followers, list) {
+               if (follower->after_panel_enabled)
+                       continue;
+
                ret = follower->funcs->panel_prepared(follower);
                if (ret < 0)
                        dev_info(panel->dev, "%ps failed: %d\n",
@@ -178,6 +181,9 @@ void drm_panel_unprepare(struct drm_panel *panel)
        mutex_lock(&panel->follower_lock);
 
        list_for_each_entry(follower, &panel->followers, list) {
+               if (follower->after_panel_enabled)
+                       continue;
+
                ret = follower->funcs->panel_unpreparing(follower);
                if (ret < 0)
                        dev_info(panel->dev, "%ps failed: %d\n",
@@ -208,6 +214,7 @@ EXPORT_SYMBOL(drm_panel_unprepare);
  */
 void drm_panel_enable(struct drm_panel *panel)
 {
+       struct drm_panel_follower *follower;
        int ret;
 
        if (!panel)
@@ -218,10 +225,12 @@ void drm_panel_enable(struct drm_panel *panel)
                return;
        }
 
+       mutex_lock(&panel->follower_lock);
+
        if (panel->funcs && panel->funcs->enable) {
                ret = panel->funcs->enable(panel);
                if (ret < 0)
-                       return;
+                       goto exit;
        }
        panel->enabled = true;
 
@@ -229,6 +238,18 @@ void drm_panel_enable(struct drm_panel *panel)
        if (ret < 0)
                DRM_DEV_INFO(panel->dev, "failed to enable backlight: %d\n",
                             ret);
+
+       list_for_each_entry(follower, &panel->followers, list) {
+               if (!follower->after_panel_enabled)
+                       continue;
+
+               ret = follower->funcs->panel_prepared(follower);
+               if (ret < 0)
+                       dev_info(panel->dev, "%ps failed: %d\n",
+                                follower->funcs->panel_prepared, ret);
+       }
+exit:
+       mutex_unlock(&panel->follower_lock);
 }
 EXPORT_SYMBOL(drm_panel_enable);
 
@@ -242,6 +263,7 @@ EXPORT_SYMBOL(drm_panel_enable);
  */
 void drm_panel_disable(struct drm_panel *panel)
 {
+       struct drm_panel_follower *follower;
        int ret;
 
        if (!panel)
@@ -261,6 +283,18 @@ void drm_panel_disable(struct drm_panel *panel)
                return;
        }
 
+       mutex_lock(&panel->follower_lock);
+
+       list_for_each_entry(follower, &panel->followers, list) {
+               if (!follower->after_panel_enabled)
+                       continue;
+
+               ret = follower->funcs->panel_unpreparing(follower);
+               if (ret < 0)
+                       dev_info(panel->dev, "%ps failed: %d\n",
+                                follower->funcs->panel_unpreparing, ret);
+       }
+
        ret = backlight_disable(panel->backlight);
        if (ret < 0)
                DRM_DEV_INFO(panel->dev, "failed to disable backlight: %d\n",
@@ -269,9 +303,12 @@ void drm_panel_disable(struct drm_panel *panel)
        if (panel->funcs && panel->funcs->disable) {
                ret = panel->funcs->disable(panel);
                if (ret < 0)
-                       return;
+                       goto exit;
        }
        panel->enabled = false;
+
+exit:
+       mutex_unlock(&panel->follower_lock);
 }
 EXPORT_SYMBOL(drm_panel_disable);
 
@@ -537,7 +574,8 @@ int drm_panel_add_follower(struct device *follower_dev,
        mutex_lock(&panel->follower_lock);
 
        list_add_tail(&follower->list, &panel->followers);
-       if (panel->prepared) {
+       if ((panel->prepared && !follower->after_panel_enabled) ||
+           (panel->enabled && follower->after_panel_enabled)) {
                ret = follower->funcs->panel_prepared(follower);
                if (ret < 0)
                        dev_info(panel->dev, "%ps failed: %d\n",
@@ -566,7 +604,8 @@ void drm_panel_remove_follower(struct drm_panel_follower 
*follower)
 
        mutex_lock(&panel->follower_lock);
 
-       if (panel->prepared) {
+       if ((panel->prepared && !follower->after_panel_enabled) ||
+           (panel->enabled && follower->after_panel_enabled)) {
                ret = follower->funcs->panel_unpreparing(follower);
                if (ret < 0)
                        dev_info(panel->dev, "%ps failed: %d\n",
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 843fb756a2950..aa9b6218702fd 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -183,6 +183,14 @@ struct drm_panel_follower {
         * The panel we're dependent on; set by drm_panel_add_follower().
         */
        struct drm_panel *panel;
+
+       /**
+        * @after_panel_enabled
+        *
+        * If true then this panel follower should be powered after the panel
+        * and the backlight are enabled, instead of after panel is prepared.
+        */
+       bool after_panel_enabled;
 };
 
 /**
-- 
2.50.1.552.g942d659e1b-goog