[PATCH] drm: do not call detect for connectors which are forced on

[Michael Rodin]

"detect" should not be called and its return value shall not be used when a
connector is forced as hinted in the commit d50ba256b5f1 ("drm/kms: start
adding command line interface using fb.") and the commit 6fe14acd496e
("drm: Document drm_connector_funcs"). One negative side effect of doing
this is observed on the RCar3 SoCs which use the dw-hdmi driver. It
continues executing drm_helper_hpd_irq_event even if its connector is
forced to ON. As consequence drm_helper_hpd_irq_event calls "detect" so the
connector status is updated to "disconnected":

[  420.201527] [drm:drm_helper_hpd_irq_event] [CONNECTOR:76:HDMI-A-1] status updated from connected to disconnected

This status is corrected by drm_helper_probe_single_connector_modes shortly
after this because this function checks if a connector is forced:

[  420.218703] [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:76:HDMI-A-1] status updated from disconnected to connected

To avoid similar issues this commit adapts functions which call "detect"
so they check if a connector is forced and return the correct status.

Fixes: 949f08862d66 ("drm: Make the connector .detect() callback optional")
Signed-off-by: Michael Rodin <mrodin at de.adit-jv.com>
---
 drivers/gpu/drm/drm_probe_helper.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index bb427c5a4f1f..1691047d0472 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -289,7 +289,12 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
 retry:
 	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
 	if (!ret) {
-		if (funcs->detect_ctx)
+		if (connector->force == DRM_FORCE_ON ||
+		    connector->force == DRM_FORCE_ON_DIGITAL)
+			ret = connector_status_connected;
+		else if (connector->force == DRM_FORCE_OFF)
+			ret = connector_status_disconnected;
+		else if (funcs->detect_ctx)
 			ret = funcs->detect_ctx(connector, &ctx, force);
 		else if (connector->funcs->detect)
 			ret = connector->funcs->detect(connector, force);
@@ -340,7 +345,14 @@ drm_helper_probe_detect(struct drm_connector *connector,
 	if (ret)
 		return ret;
 
-	if (funcs->detect_ctx)
+	if (connector->force == DRM_FORCE_ON ||
+	    connector->force == DRM_FORCE_ON_DIGITAL)
+		ret = connector_status_connected;
+	else if (connector->force == DRM_FORCE_OFF)
+		ret = connector_status_disconnected;
+	else if (funcs->detect_ctx)
+		ret = funcs->detect_ctx(connector, ctx, force);
+	else if (funcs->detect_ctx)
 		ret = funcs->detect_ctx(connector, ctx, force);
 	else if (connector->funcs->detect)
 		ret = connector->funcs->detect(connector, force);
-- 
2.25.1