[PATCH] drm/exynos/dsi: simplify hotplug code

[Andrzej Hajda]

Exynos DSI driver uses DSI bus attach/detach callbacks to implement
panel hotplug mechanism. The patch moves panel attachment code
from .detect callback to DSI bus callbacks. It makes the code
simpler and more straightforward.
The patch removes also redundant and lock unprotected dpms_off call
from unbind code.

Signed-off-by: Andrzej Hajda <a.hajda at samsung.com>
---
Hi,

This patch simplifies drm part of hotplug mechanism in dsi attach/detach callbacks.
It also fixes minor bug with unprotected dpms_off call, which is unneccesary anyway.

But the main reason I have looked at this code again is to show that
we do not need zombie panels, we can kill panels properly if we have hot plug/unplug
callbacks. And it is quite simple: we just need to take mode_config.mutex locks
to synchronize dsi callbacks with drm, nothing more.
It works nicely because of two things:
- panel callbacks are called always under this lock,
- callbacks are installed after drmdev creation and deinstalled before drmdev destroy - 
this way we assure drmdev is always present in callbacks.

Regards
Andrzej

 drivers/gpu/drm/exynos/exynos_drm_dsi.c | 61 ++++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
index 5e38d15..60306c1 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
@@ -271,7 +271,6 @@ struct exynos_dsi {
 	struct exynos_drm_display display;
 	struct mipi_dsi_host dsi_host;
 	struct drm_connector connector;
-	struct device_node *panel_node;
 	struct drm_panel *panel;
 	struct device *dev;
 
@@ -1147,9 +1146,10 @@ static int exynos_dsi_init(struct exynos_dsi *dsi)
 
 static int exynos_dsi_register_te_irq(struct exynos_dsi *dsi)
 {
+	struct device_node *panel_node = dsi->panel->dev->of_node;
 	int ret;
 
-	dsi->te_gpio = of_get_named_gpio(dsi->panel_node, "te-gpios", 0);
+	dsi->te_gpio = of_get_named_gpio(panel_node, "te-gpios", 0);
 	if (!gpio_is_valid(dsi->te_gpio)) {
 		dev_err(dsi->dev, "no te-gpios specified\n");
 		ret = dsi->te_gpio;
@@ -1194,14 +1194,28 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
 				  struct mipi_dsi_device *device)
 {
 	struct exynos_dsi *dsi = host_to_dsi(host);
+	struct drm_device *drm_dev = dsi->connector.dev;
+	bool changed = false;
 
 	dsi->lanes = device->lanes;
 	dsi->format = device->format;
 	dsi->mode_flags = device->mode_flags;
-	dsi->panel_node = device->dev.of_node;
 
-	if (dsi->connector.dev)
-		drm_helper_hpd_irq_event(dsi->connector.dev);
+	mutex_lock(&drm_dev->mode_config.mutex);
+
+	dsi->panel = of_drm_find_panel(device->dev.of_node);
+	if (dsi->panel) {
+		drm_panel_attach(dsi->panel, &dsi->connector);
+		if (drm_dev->mode_config.poll_enabled) {
+			dsi->connector.status = connector_status_connected;
+			changed = true;
+		}
+	}
+
+	mutex_unlock(&drm_dev->mode_config.mutex);
+
+	if (changed)
+		drm_kms_helper_hotplug_event(drm_dev);
 
 	/*
 	 * This is a temporary solution and should be made by more generic way.
@@ -1223,13 +1237,29 @@ static int exynos_dsi_host_detach(struct mipi_dsi_host *host,
 				  struct mipi_dsi_device *device)
 {
 	struct exynos_dsi *dsi = host_to_dsi(host);
+	struct drm_device *drm_dev = dsi->connector.dev;
+	struct exynos_drm_display *display = dev_get_drvdata(dsi->dev);
+	bool changed = false;
 
 	exynos_dsi_unregister_te_irq(dsi);
 
-	dsi->panel_node = NULL;
+	mutex_lock(&drm_dev->mode_config.mutex);
+
+	display->ops->dpms(display, DRM_MODE_DPMS_OFF);
+
+	if (dsi->panel) {
+		drm_panel_detach(dsi->panel);
+		dsi->panel = NULL;
+		if (drm_dev->mode_config.poll_enabled) {
+			dsi->connector.status = connector_status_disconnected;
+			changed = true;
+		}
+	}
+
+	mutex_unlock(&drm_dev->mode_config.mutex);
 
-	if (dsi->connector.dev)
-		drm_helper_hpd_irq_event(dsi->connector.dev);
+	if (changed)
+		drm_kms_helper_hotplug_event(drm_dev);
 
 	return 0;
 }
@@ -1425,19 +1455,6 @@ exynos_dsi_detect(struct drm_connector *connector, bool force)
 {
 	struct exynos_dsi *dsi = connector_to_dsi(connector);
 
-	if (!dsi->panel) {
-		dsi->panel = of_drm_find_panel(dsi->panel_node);
-		if (dsi->panel)
-			drm_panel_attach(dsi->panel, &dsi->connector);
-	} else if (!dsi->panel_node) {
-		struct exynos_drm_display *display;
-
-		display = platform_get_drvdata(to_platform_device(dsi->dev));
-		exynos_dsi_dpms(display, DRM_MODE_DPMS_OFF);
-		drm_panel_detach(dsi->panel);
-		dsi->panel = NULL;
-	}
-
 	if (dsi->panel)
 		return connector_status_connected;
 
@@ -1660,8 +1677,6 @@ static void exynos_dsi_unbind(struct device *dev, struct device *master,
 	struct exynos_drm_display *display = dev_get_drvdata(dev);
 	struct exynos_dsi *dsi = display_to_dsi(display);
 
-	exynos_dsi_dpms(display, DRM_MODE_DPMS_OFF);
-
 	mipi_dsi_host_unregister(&dsi->dsi_host);
 }
 
-- 
1.9.1