[PATCH 2/2] drm/probe_helper: Add drm_helper_probe_single_connector_modes_with_rpm()

[Lyude Paul]

For nouveau, while the GPU is guaranteed to be on when a hotplug has
been received, the same assertion does not hold true if a connector
probe has been started by userspace without having had received a sysfs
event.

So ensure that any connector probing keeps the GPU alive for the
duration of the probe by introducing
drm_helper_probe_single_connector_modes_with_rpm(). It's the same as
drm_helper_probe_single_connector_modes, but it handles holding a power
reference to the device for the duration of the connector probe.

Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
Reviewed-by: Karol Herbst <karolherbst@xxxxxxxxx>
Cc: Lukas Wunner <lukas@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
Changes since v1:
 - Add a generic helper to DRM to handle this

 drivers/gpu/drm/drm_probe_helper.c          | 31 +++++++++++++++++++++
 drivers/gpu/drm/nouveau/dispnv50/disp.c     |  2 +-
 drivers/gpu/drm/nouveau/nouveau_connector.c |  4 +--
 include/drm/drm_crtc_helper.h               |  7 +++--
 4 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 527743394150..0a9d6748b854 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -31,6 +31,7 @@
 
 #include <linux/export.h>
 #include <linux/moduleparam.h>
+#include <linux/pm_runtime.h>
 
 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
@@ -541,6 +542,36 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);
 
+/**
+ * drm_helper_probe_single_connector_modes_with_rpm - get complete set of
+ *                                                    display modes
+ * @connector: connector to probe
+ * @maxX: max width for modes
+ * @maxY: max height for modes
+ *
+ * Same as drm_helper_probe_single_connector_modes, except that it makes sure
+ * that the device is active by synchronously grabbing a runtime power
+ * reference while probing.
+ *
+ * Returns:
+ * The number of modes found on @connector.
+ */
+int drm_helper_probe_single_connector_modes_with_rpm(struct drm_connector *connector,
+						     uint32_t maxX, uint32_t maxY)
+{
+	int ret;
+
+	ret = pm_runtime_get_sync(connector->dev->dev);
+	if (ret < 0 && ret != -EACCES)
+		return ret;
+
+	ret = drm_helper_probe_single_connector_modes(connector, maxX, maxY);
+
+	pm_runtime_put(connector->dev->dev);
+	return ret;
+}
+EXPORT_SYMBOL(drm_helper_probe_single_connector_modes_with_rpm);
+
 /**
  * drm_kms_helper_hotplug_event - fire off KMS hotplug events
  * @dev: drm_device whose connector state changed
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index fa3ab618a0f9..c54767b50fd8 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -858,7 +858,7 @@ static const struct drm_connector_funcs
 nv50_mstc = {
 	.reset = nouveau_conn_reset,
 	.detect = nv50_mstc_detect,
-	.fill_modes = drm_helper_probe_single_connector_modes,
+	.fill_modes = drm_helper_probe_single_connector_modes_with_rpm,
 	.destroy = nv50_mstc_destroy,
 	.atomic_duplicate_state = nouveau_conn_atomic_duplicate_state,
 	.atomic_destroy_state = nouveau_conn_atomic_destroy_state,
diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 2a45b4c2ceb0..8d9070779261 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -1088,7 +1088,7 @@ nouveau_connector_funcs = {
 	.reset = nouveau_conn_reset,
 	.detect = nouveau_connector_detect,
 	.force = nouveau_connector_force,
-	.fill_modes = drm_helper_probe_single_connector_modes,
+	.fill_modes = drm_helper_probe_single_connector_modes_with_rpm,
 	.set_property = nouveau_connector_set_property,
 	.destroy = nouveau_connector_destroy,
 	.atomic_duplicate_state = nouveau_conn_atomic_duplicate_state,
@@ -1103,7 +1103,7 @@ nouveau_connector_funcs_lvds = {
 	.reset = nouveau_conn_reset,
 	.detect = nouveau_connector_detect_lvds,
 	.force = nouveau_connector_force,
-	.fill_modes = drm_helper_probe_single_connector_modes,
+	.fill_modes = drm_helper_probe_single_connector_modes_with_rpm,
 	.set_property = nouveau_connector_set_property,
 	.destroy = nouveau_connector_destroy,
 	.atomic_duplicate_state = nouveau_conn_atomic_duplicate_state,
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 6914633037a5..8f3f6d6fcc8c 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -64,9 +64,10 @@ int drm_helper_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
 				  struct drm_framebuffer *old_fb);
 
 /* drm_probe_helper.c */
-int drm_helper_probe_single_connector_modes(struct drm_connector
-					    *connector, uint32_t maxX,
-					    uint32_t maxY);
+int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
+					    uint32_t maxX, uint32_t maxY);
+int drm_helper_probe_single_connector_modes_with_rpm(struct drm_connector *connector,
+						     uint32_t maxX, uint32_t maxY);
 int drm_helper_probe_detect(struct drm_connector *connector,
 			    struct drm_modeset_acquire_ctx *ctx,
 			    bool force);
-- 
2.17.1