[PATCH] drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

mode_valid() and get_modes() called
from drm_helper_probe_single_connector_modes()
may need to look at connector->state because what a valid mode is may
depend on connector properties being set. For example some HDMI modes
might be rejected when a connector property forces the connector
into DVI mode.

Some implementations of detect() already lock all state,
so we have to pass an acquire_ctx to them to prevent a deadlock.

This means changing the function signature of detect() slightly,
and passing the acquire_ctx for locking multiple crtc's.
It might be NULL, in which case expensive operations should be avoided.

intel_dp.c however ignores the force flag, so still lock
connection_mutex there if needed.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_probe_helper.c   | 41 ++++++++++++++++++++++++++++++------
 drivers/gpu/drm/i915/intel_crt.c     | 29 +++++++++++++------------
 drivers/gpu/drm/i915/intel_display.c | 25 +++++++++++-----------
 drivers/gpu/drm/i915/intel_dp.c      | 22 ++++++++++++-------
 drivers/gpu/drm/i915/intel_drv.h     |  8 +++----
 drivers/gpu/drm/i915/intel_hotplug.c |  6 +++++-
 drivers/gpu/drm/i915/intel_tv.c      | 24 ++++++++++-----------
 include/drm/drm_connector.h          |  5 +++++
 8 files changed, 101 insertions(+), 59 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 85005d57bde6..a48cff963871 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -169,11 +169,15 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
 EXPORT_SYMBOL(drm_kms_helper_poll_enable);
 
 static enum drm_connector_status
-drm_connector_detect(struct drm_connector *connector, bool force)
+drm_connector_detect(struct drm_connector *connector,
+		     struct drm_modeset_acquire_ctx *ctx)
 {
-	return connector->funcs->detect ?
-		connector->funcs->detect(connector, force) :
-		connector_status_connected;
+	if (connector->funcs->detect_ctx)
+		return connector->funcs->detect_ctx(connector, ctx);
+	else if (connector->funcs->detect)
+		return connector->funcs->detect(connector, !!ctx);
+	else
+		return connector_status_connected;
 }
 
 /**
@@ -239,15 +243,27 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 	struct drm_display_mode *mode;
 	const struct drm_connector_helper_funcs *connector_funcs =
 		connector->helper_private;
-	int count = 0;
+	int count = 0, ret;
 	int mode_flags = 0;
 	bool verbose_prune = true;
 	enum drm_connector_status old_status;
+	struct drm_modeset_acquire_ctx ctx;
 
 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
 
+	drm_modeset_acquire_init(&ctx, 0);
+
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
 			connector->name);
+
+retry:
+	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
+	if (ret == -EDEADLK) {
+		drm_modeset_backoff(&ctx);
+		goto retry;
+	} else
+		WARN_ON(ret < 0);
+
 	/* set all old modes to the stale state */
 	list_for_each_entry(mode, &connector->modes, head)
 		mode->status = MODE_STALE;
@@ -263,7 +279,15 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 		if (connector->funcs->force)
 			connector->funcs->force(connector);
 	} else {
-		connector->status = drm_connector_detect(connector, true);
+		ret = drm_connector_detect(connector, &ctx);
+
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(&ctx);
+			goto retry;
+		} else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
+			ret = connector_status_unknown;
+
+		connector->status = ret;
 	}
 
 	/*
@@ -355,6 +379,9 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 prune:
 	drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
 
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+
 	if (list_empty(&connector->modes))
 		return 0;
 
@@ -440,7 +467,7 @@ static void output_poll_execute(struct work_struct *work)
 
 		repoll = true;
 
-		connector->status = drm_connector_detect(connector, false);
+		connector->status = drm_connector_detect(connector, NULL);
 		if (old_status != connector->status) {
 			const char *old, *new;
 
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 8c82607294c6..1186c3f5fea0 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -669,19 +669,19 @@ static const struct dmi_system_id intel_spurious_crt_detect[] = {
 	{ }
 };
 
-static enum drm_connector_status
-intel_crt_detect(struct drm_connector *connector, bool force)
+static int
+intel_crt_detect(struct drm_connector *connector,
+		 struct drm_modeset_acquire_ctx *ctx)
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->dev);
 	struct intel_crt *crt = intel_attached_crt(connector);
 	struct intel_encoder *intel_encoder = &crt->base;
-	enum drm_connector_status status;
+	int status, ret;
 	struct intel_load_detect_pipe tmp;
-	struct drm_modeset_acquire_ctx ctx;
 
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] force=%d\n",
 		      connector->base.id, connector->name,
-		      force);
+		      !!ctx);
 
 	/* Skip machines without VGA that falsely report hotplug events */
 	if (dmi_check_system(intel_spurious_crt_detect))
@@ -716,15 +716,19 @@ intel_crt_detect(struct drm_connector *connector, bool force)
 		goto out;
 	}
 
-	if (!force) {
+	if (!ctx) {
 		status = connector->status;
 		goto out;
 	}
 
-	drm_modeset_acquire_init(&ctx, 0);
-
 	/* for pre-945g platforms use load detect */
-	if (intel_get_load_detect_pipe(connector, NULL, &tmp, &ctx)) {
+	ret = intel_get_load_detect_pipe(connector, NULL, &tmp, ctx);
+	if (ret < 0) {
+		status = ret;
+		goto out;
+	}
+
+	if (ret > 0) {
 		if (intel_crt_detect_ddc(connector))
 			status = connector_status_connected;
 		else if (INTEL_GEN(dev_priv) < 4)
@@ -734,13 +738,10 @@ intel_crt_detect(struct drm_connector *connector, bool force)
 			status = connector_status_disconnected;
 		else
 			status = connector_status_unknown;
-		intel_release_load_detect_pipe(connector, &tmp, &ctx);
+		intel_release_load_detect_pipe(connector, &tmp, ctx);
 	} else
 		status = connector_status_unknown;
 
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
-
 out:
 	intel_display_power_put(dev_priv, intel_encoder->power_domain);
 	return status;
@@ -811,7 +812,7 @@ void intel_crt_reset(struct drm_encoder *encoder)
 
 static const struct drm_connector_funcs intel_crt_connector_funcs = {
 	.dpms = drm_atomic_helper_connector_dpms,
-	.detect = intel_crt_detect,
+	.detect_ctx = intel_crt_detect,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.late_register = intel_connector_register,
 	.early_unregister = intel_connector_unregister,
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a79063fac951..baa8d836c8e7 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9503,10 +9503,10 @@ static int intel_modeset_setup_plane_state(struct drm_atomic_state *state,
 	return 0;
 }
 
-bool intel_get_load_detect_pipe(struct drm_connector *connector,
-				struct drm_display_mode *mode,
-				struct intel_load_detect_pipe *old,
-				struct drm_modeset_acquire_ctx *ctx)
+int intel_get_load_detect_pipe(struct drm_connector *connector,
+			       struct drm_display_mode *mode,
+			       struct intel_load_detect_pipe *old,
+			       struct drm_modeset_acquire_ctx *ctx)
 {
 	struct intel_crtc *intel_crtc;
 	struct intel_encoder *intel_encoder =
@@ -9529,10 +9529,7 @@ bool intel_get_load_detect_pipe(struct drm_connector *connector,
 
 	old->restore_state = NULL;
 
-retry:
-	ret = drm_modeset_lock(&config->connection_mutex, ctx);
-	if (ret)
-		goto fail;
+	WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
 
 	/*
 	 * Algorithm gets a little messy:
@@ -9682,10 +9679,8 @@ bool intel_get_load_detect_pipe(struct drm_connector *connector,
 		restore_state = NULL;
 	}
 
-	if (ret == -EDEADLK) {
-		drm_modeset_backoff(ctx);
-		goto retry;
-	}
+	if (ret == -EDEADLK)
+		return ret;
 
 	return false;
 }
@@ -15112,6 +15107,7 @@ static void intel_enable_pipe_a(struct drm_device *dev)
 	struct drm_connector *crt = NULL;
 	struct intel_load_detect_pipe load_detect_temp;
 	struct drm_modeset_acquire_ctx *ctx = dev->mode_config.acquire_ctx;
+	int ret;
 
 	/* We can't just switch on the pipe A, we need to set things up with a
 	 * proper mode and output configuration. As a gross hack, enable pipe A
@@ -15128,7 +15124,10 @@ static void intel_enable_pipe_a(struct drm_device *dev)
 	if (!crt)
 		return;
 
-	if (intel_get_load_detect_pipe(crt, NULL, &load_detect_temp, ctx))
+	ret = intel_get_load_detect_pipe(crt, NULL, &load_detect_temp, ctx);
+	WARN(ret < 0, "All modeset mutexes are locked, but intel_get_load_detect_pipe failed\n");
+
+	if (ret > 0)
 		intel_release_load_detect_pipe(crt, &load_detect_temp, ctx);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fd96a6cf7326..10b3727b7381 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4567,7 +4567,8 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 }
 
 static enum drm_connector_status
-intel_dp_long_pulse(struct intel_connector *intel_connector)
+intel_dp_long_pulse(struct intel_connector *intel_connector,
+		    struct drm_modeset_acquire_ctx *ctx)
 {
 	struct drm_connector *connector = &intel_connector->base;
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
@@ -4640,9 +4641,13 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 		 * check links status, there has been known issues of
 		 * link loss triggerring long pulse!!!!
 		 */
-		drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+		if (!ctx)
+			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+
 		intel_dp_check_link_status(intel_dp);
-		drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+		if (!ctx)
+			drm_modeset_unlock(&dev->mode_config.connection_mutex);
 		goto out;
 	}
 
@@ -4682,18 +4687,19 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 	return status;
 }
 
-static enum drm_connector_status
-intel_dp_detect(struct drm_connector *connector, bool force)
+static int
+intel_dp_detect(struct drm_connector *connector,
+		struct drm_modeset_acquire_ctx *ctx)
 {
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
-	enum drm_connector_status status = connector->status;
+	int status = connector->status;
 
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
 	/* If full detect is not performed yet, do a full detect */
 	if (!intel_dp->detect_done)
-		status = intel_dp_long_pulse(intel_dp->attached_connector);
+		status = intel_dp_long_pulse(intel_dp->attached_connector, ctx);
 
 	intel_dp->detect_done = false;
 
@@ -5014,7 +5020,7 @@ void intel_dp_encoder_reset(struct drm_encoder *encoder)
 
 static const struct drm_connector_funcs intel_dp_connector_funcs = {
 	.dpms = drm_atomic_helper_connector_dpms,
-	.detect = intel_dp_detect,
+	.detect_ctx = intel_dp_detect,
 	.force = intel_dp_force,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.set_property = intel_dp_set_property,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index e24641b559e2..6ea8b9cd68c5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1362,10 +1362,10 @@ int ironlake_get_lanes_required(int target_clock, int link_bw, int bpp);
 void vlv_wait_port_ready(struct drm_i915_private *dev_priv,
 			 struct intel_digital_port *dport,
 			 unsigned int expected_mask);
-bool intel_get_load_detect_pipe(struct drm_connector *connector,
-				struct drm_display_mode *mode,
-				struct intel_load_detect_pipe *old,
-				struct drm_modeset_acquire_ctx *ctx);
+int intel_get_load_detect_pipe(struct drm_connector *connector,
+			       struct drm_display_mode *mode,
+			       struct intel_load_detect_pipe *old,
+			       struct drm_modeset_acquire_ctx *ctx);
 void intel_release_load_detect_pipe(struct drm_connector *connector,
 				    struct intel_load_detect_pipe *old,
 				    struct drm_modeset_acquire_ctx *ctx);
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 7d210097eefa..d2d2af7ef305 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -243,7 +243,11 @@ static bool intel_hpd_irq_event(struct drm_device *dev,
 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
 	old_status = connector->status;
 
-	connector->status = connector->funcs->detect(connector, false);
+	if (connector->funcs->detect_ctx)
+		connector->status = connector->funcs->detect_ctx(connector, NULL);
+	else
+		connector->status = connector->funcs->detect(connector, false);
+
 	if (old_status == connector->status)
 		return false;
 
diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 6ed1a3ce47b7..d2c0120048b2 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1315,8 +1315,9 @@ static void intel_tv_find_better_format(struct drm_connector *connector)
  * Currently this always returns CONNECTOR_STATUS_UNKNOWN, as we need to be sure
  * we have a pipe programmed in order to probe the TV.
  */
-static enum drm_connector_status
-intel_tv_detect(struct drm_connector *connector, bool force)
+static int
+intel_tv_detect(struct drm_connector *connector,
+		struct drm_modeset_acquire_ctx *ctx)
 {
 	struct drm_display_mode mode;
 	struct intel_tv *intel_tv = intel_attached_tv(connector);
@@ -1325,27 +1326,26 @@ intel_tv_detect(struct drm_connector *connector, bool force)
 
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] force=%d\n",
 		      connector->base.id, connector->name,
-		      force);
+		      !!ctx);
 
 	mode = reported_modes[0];
 
-	if (force) {
+	if (ctx) {
 		struct intel_load_detect_pipe tmp;
-		struct drm_modeset_acquire_ctx ctx;
+		int ret;
 
-		drm_modeset_acquire_init(&ctx, 0);
+		ret = intel_get_load_detect_pipe(connector, &mode, &tmp, ctx);
+		if (ret < 0)
+			return ret;
 
-		if (intel_get_load_detect_pipe(connector, &mode, &tmp, &ctx)) {
+		if (ret > 0) {
 			type = intel_tv_detect_type(intel_tv, connector);
-			intel_release_load_detect_pipe(connector, &tmp, &ctx);
+			intel_release_load_detect_pipe(connector, &tmp, ctx);
 			status = type < 0 ?
 				connector_status_disconnected :
 				connector_status_connected;
 		} else
 			status = connector_status_unknown;
-
-		drm_modeset_drop_locks(&ctx);
-		drm_modeset_acquire_fini(&ctx);
 	} else
 		return connector->status;
 
@@ -1516,7 +1516,7 @@ intel_tv_set_property(struct drm_connector *connector, struct drm_property *prop
 
 static const struct drm_connector_funcs intel_tv_connector_funcs = {
 	.dpms = drm_atomic_helper_connector_dpms,
-	.detect = intel_tv_detect,
+	.detect_ctx = intel_tv_detect,
 	.late_register = intel_connector_register,
 	.early_unregister = intel_connector_unregister,
 	.destroy = intel_tv_destroy,
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 941f57f311aa..834d1ba709ea 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -32,6 +32,7 @@
 struct drm_device;
 
 struct drm_connector_helper_funcs;
+struct drm_modeset_acquire_ctx;
 struct drm_device;
 struct drm_crtc;
 struct drm_encoder;
@@ -385,6 +386,10 @@ struct drm_connector_funcs {
 	enum drm_connector_status (*detect)(struct drm_connector *connector,
 					    bool force);
 
+	/* ctx = NULL <> detect(force = false), but may also return -EDEADLK. */
+	int (*detect_ctx)(struct drm_connector *connector,
+			  struct drm_modeset_acquire_ctx *ctx);
+
 	/**
 	 * @force:
 	 *
-- 
2.7.4

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