drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes, v4.
mode_valid() 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.
For the callbacks, it will always be non-zero. To allow callers
not to worry about this, drm_helper_probe_detect_ctx is added
which might handle -EDEADLK for you.
Changes since v1:
- Always set ctx parameter.
Changes since v2:
- Always take connection_mutex when probing.
Changes since v3:
- Remove the ctx from intel_dp_long_pulse, and add
WARN_ON(!connection_mutex) (danvet)
- Update docs to clarify the locking situation. (danvet)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1491504920-4017-1-git-send-email-maarten.lankhorst@linux.intel.com
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 941f57f..e2ee74c 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;
@@ -378,6 +379,11 @@
* the helper library vtable purely for historical reasons. The only DRM
* core entry point to probe connector state is @fill_modes.
*
+ * Note that the helper library will already hold
+ * &drm_mode_config.connection_mutex. Drivers which need to grab additional
+ * locks to avoid races with concurrent modeset changes need to use
+ * &drm_connector_helper_funcs.detect_ctx instead.
+ *
* RETURNS:
*
* drm_connector_status indicating the connector's status.
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 43505c7..76e237b 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -67,6 +67,9 @@
int drm_helper_probe_single_connector_modes(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);
void drm_kms_helper_poll_init(struct drm_device *dev);
void drm_kms_helper_poll_fini(struct drm_device *dev);
bool drm_helper_hpd_irq_event(struct drm_device *dev);
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 091c422..7847bab 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -747,6 +747,10 @@
* This callback is used by the probe helpers in e.g.
* drm_helper_probe_single_connector_modes().
*
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
* RETURNS:
*
* The number of modes added by calling drm_mode_probed_add().
@@ -754,6 +758,34 @@
int (*get_modes)(struct drm_connector *connector);
/**
+ * @detect_ctx:
+ *
+ * Check to see if anything is attached to the connector. The parameter
+ * force is set to false whilst polling, true when checking the
+ * connector due to a user request. force can be used by the driver to
+ * avoid expensive, destructive operations during automated probing.
+ *
+ * This callback is optional, if not implemented the connector will be
+ * considered as always being attached.
+ *
+ * This is the atomic version of &drm_connector_funcs.detect.
+ *
+ * To avoid races against concurrent connector state updates, the
+ * helper libraries always call this with ctx set to a valid context,
+ * and &drm_mode_config.connection_mutex will always be locked with
+ * the ctx parameter set to this ctx. This allows taking additional
+ * locks as required.
+ *
+ * RETURNS:
+ *
+ * &drm_connector_status indicating the connector's status,
+ * or the error code returned by drm_modeset_lock(), -EDEADLK.
+ */
+ int (*detect_ctx)(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force);
+
+ /**
* @mode_valid:
*
* Callback to validate a mode for a connector, irrespective of the
@@ -771,6 +803,10 @@
* CRTC helpers will not call this function. Drivers therefore must
* still fully validate any mode passed in in a modeset request.
*
+ * To avoid races with concurrent connector state updates, the helper
+ * libraries always call this with the &drm_mode_config.connection_mutex
+ * held. Because of this it's safe to inspect &drm_connector->state.
+ *
* RETURNS:
*
* Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum