[PATCH v6 1/6] drm: sun4i: dsi: Drop DRM bind race with bridge attach

[Jagan Teki]

Existing host driver will keep looking for DRM pointer in
sun6i_dsi_attach and defers even if the particular DSI device
is found for the first time. Meanwhile it triggers the bind
callback and gets the DRM pointer and then continues the
sun6i_dsi_attach.

This makes a deadlock situation if sun6i_dsi_attach is trying
to find the bridge.

If interface bridge is trying to call host attach, then host
sun6i_dsi_attach is trying to find bridge and defers the
interface bridge even if it found the bridge as bind callback
does not complete at the movement. So, this sun6i_dsi_attach
defers interface bridge and triggers the bind callback and
tries to attach the bridge with a bridge pointer which is not
available at the moment.

Eventually these callbacks are triggered recursively, as
sun6i_dsi_attach defers interface bridge and bind callback
defers sun6i_dsi_attach due to invalid bridge ponter.

This patch prevents this situation by probing all DSI devices
on the pipeline first and then triggers the bind callback by
dropping exing DRM binding logic.

Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
---
Changes for v6:
- none
Changes for v5:
- new patch

 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 10 +---------
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 -
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 527c7b2474da..4bdcce8f1d84 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -967,14 +967,10 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
 
 	if (IS_ERR(panel))
 		return PTR_ERR(panel);
-	if (!dsi->drm || !dsi->drm->registered)
-		return -EPROBE_DEFER;
 
 	dsi->panel = panel;
 	dsi->device = device;
 
-	drm_kms_helper_hotplug_event(dsi->drm);
-
 	dev_info(host->dev, "Attached device %s\n", device->name);
 
 	return 0;
@@ -988,8 +984,6 @@ static int sun6i_dsi_detach(struct mipi_dsi_host *host,
 	dsi->panel = NULL;
 	dsi->device = NULL;
 
-	drm_kms_helper_hotplug_event(dsi->drm);
-
 	return 0;
 }
 
@@ -1077,8 +1071,6 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
 
 	drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
 
-	dsi->drm = drm;
-
 	return 0;
 
 err_cleanup_connector:
@@ -1091,7 +1083,7 @@ static void sun6i_dsi_unbind(struct device *dev, struct device *master,
 {
 	struct sun6i_dsi *dsi = dev_get_drvdata(dev);
 
-	dsi->drm = NULL;
+	drm_encoder_cleanup(&dsi->encoder);
 }
 
 static const struct component_ops sun6i_dsi_ops = {
diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
index c863900ae3b4..61e88ea6044d 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
@@ -29,7 +29,6 @@ struct sun6i_dsi {
 
 	struct device		*dev;
 	struct mipi_dsi_device	*device;
-	struct drm_device	*drm;
 	struct drm_panel	*panel;
 };
 
-- 
2.25.1