[PATCH v2] drm/bridge: analogix: protect power when get_modes or detect

[Mark Yao]

The drm callback ->detect and ->get_modes seems is not power safe,
they may be called when device is power off, do register access on
detect or get_modes will cause system die.

Here is the path call ->detect before analogix_dp power on
[<ffffff800843babc>] analogix_dp_detect+0x44/0xdc
[<ffffff80083fd840>] drm_helper_probe_single_connector_modes_merge_bits+0xe8/0x41c
[<ffffff80083fdb84>] drm_helper_probe_single_connector_modes+0x10/0x18
[<ffffff8008418d24>] drm_mode_getconnector+0xf4/0x304
[<ffffff800840cff0>] drm_ioctl+0x23c/0x390
[<ffffff80081a8adc>] do_vfs_ioctl+0x4b8/0x58c
[<ffffff80081a8c10>] SyS_ioctl+0x60/0x88

Cc: Inki Dae <inki.dae at samsung.com>
Cc: Sean Paul <seanpaul at chromium.org>
Cc: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
Cc: "Ville Syrjälä" <ville.syrjala at linux.intel.com>

Signed-off-by: Mark Yao <mark.yao at rock-chips.com>
---
Changes in v2:
- remove sub device power on/off callback, use pm_runtime_get/put is enough
to fix my problem, so will can avoid race to dpms.

 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index efac8ab..ff2d328 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1062,11 +1062,15 @@ int analogix_dp_get_modes(struct drm_connector *connector)
 		return 0;
 	}
 
+	pm_runtime_get_sync(dp->dev);
+
 	if (analogix_dp_handle_edid(dp) == 0) {
 		drm_mode_connector_update_edid_property(&dp->connector, edid);
 		num_modes += drm_add_edid_modes(&dp->connector, edid);
 	}
 
+	pm_runtime_put(dp->dev);
+
 	if (dp->plat_data->panel)
 		num_modes += drm_panel_get_modes(dp->plat_data->panel);
 
@@ -1106,9 +1110,13 @@ analogix_dp_detect(struct drm_connector *connector, bool force)
 		return connector_status_disconnected;
 	}
 
+	pm_runtime_get_sync(dp->dev);
+
 	if (!analogix_dp_detect_hpd(dp))
 		status = connector_status_connected;
 
+	pm_runtime_put(dp->dev);
+
 	ret = analogix_dp_prepare_panel(dp, false, false);
 	if (ret)
 		DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
-- 
1.9.1