drm/atomic-helper: Implement subsystem-level suspend/resume

Provide subsystem-level suspend and resume helpers that can be used to
implement suspend/resume on atomic mode-setting enabled drivers.

v2: simplify locking, enhance kerneldoc comments
v3: pass lock acquisition context by parameter, improve kerneldoc
v4: - remove redundant code (already provided by atomic helpers)
      (Maarten Lankhorst)
    - move backoff dance from drm_modeset_lock_all_ctx() into suspend
      helper (Daniel Vetter)
v5: handle potential EDEADLK from drm_atomic_helper_duplicate_state()
    and drm_atomic_helper_disable_all() (Daniel Vetter)

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449075005-13937-2-git-send-email-thierry.reding@gmail.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 161 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index a800b2c75522..d9053ebf4903 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1861,6 +1861,161 @@ commit:
 }
 
 /**
+ * drm_atomic_helper_disable_all - disable all currently active outputs
+ * @dev: DRM device
+ * @ctx: lock acquisition context
+ *
+ * Loops through all connectors, finding those that aren't turned off and then
+ * turns them off by setting their DPMS mode to OFF and deactivating the CRTC
+ * that they are connected to.
+ *
+ * This is used for example in suspend/resume to disable all currently active
+ * functions when suspending.
+ *
+ * Note that if callers haven't already acquired all modeset locks this might
+ * return -EDEADLK, which must be handled by calling drm_modeset_backoff().
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ *
+ * See also:
+ * drm_atomic_helper_suspend(), drm_atomic_helper_resume()
+ */
+int drm_atomic_helper_disable_all(struct drm_device *dev,
+				  struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_atomic_state *state;
+	struct drm_connector *conn;
+	int err;
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state)
+		return -ENOMEM;
+
+	state->acquire_ctx = ctx;
+
+	drm_for_each_connector(conn, dev) {
+		struct drm_crtc *crtc = conn->state->crtc;
+		struct drm_crtc_state *crtc_state;
+
+		if (!crtc || conn->dpms != DRM_MODE_DPMS_ON)
+			continue;
+
+		crtc_state = drm_atomic_get_crtc_state(state, crtc);
+		if (IS_ERR(crtc_state)) {
+			err = PTR_ERR(crtc_state);
+			goto free;
+		}
+
+		crtc_state->active = false;
+	}
+
+	err = drm_atomic_commit(state);
+
+free:
+	if (err < 0)
+		drm_atomic_state_free(state);
+
+	return err;
+}
+EXPORT_SYMBOL(drm_atomic_helper_disable_all);
+
+/**
+ * drm_atomic_helper_suspend - subsystem-level suspend helper
+ * @dev: DRM device
+ *
+ * Duplicates the current atomic state, disables all active outputs and then
+ * returns a pointer to the original atomic state to the caller. Drivers can
+ * pass this pointer to the drm_atomic_helper_resume() helper upon resume to
+ * restore the output configuration that was active at the time the system
+ * entered suspend.
+ *
+ * Note that it is potentially unsafe to use this. The atomic state object
+ * returned by this function is assumed to be persistent. Drivers must ensure
+ * that this holds true. Before calling this function, drivers must make sure
+ * to suspend fbdev emulation so that nothing can be using the device.
+ *
+ * Returns:
+ * A pointer to a copy of the state before suspend on success or an ERR_PTR()-
+ * encoded error code on failure. Drivers should store the returned atomic
+ * state object and pass it to the drm_atomic_helper_resume() helper upon
+ * resume.
+ *
+ * See also:
+ * drm_atomic_helper_duplicate_state(), drm_atomic_helper_disable_all(),
+ * drm_atomic_helper_resume()
+ */
+struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	struct drm_atomic_state *state;
+	int err;
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+retry:
+	err = drm_modeset_lock_all_ctx(dev, &ctx);
+	if (err < 0) {
+		state = ERR_PTR(err);
+		goto unlock;
+	}
+
+	state = drm_atomic_helper_duplicate_state(dev, &ctx);
+	if (IS_ERR(state))
+		goto unlock;
+
+	err = drm_atomic_helper_disable_all(dev, &ctx);
+	if (err < 0) {
+		drm_atomic_state_free(state);
+		state = ERR_PTR(err);
+		goto unlock;
+	}
+
+unlock:
+	if (PTR_ERR(state) == -EDEADLK) {
+		drm_modeset_backoff(&ctx);
+		goto retry;
+	}
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+	return state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_suspend);
+
+/**
+ * drm_atomic_helper_resume - subsystem-level resume helper
+ * @dev: DRM device
+ * @state: atomic state to resume to
+ *
+ * Calls drm_mode_config_reset() to synchronize hardware and software states,
+ * grabs all modeset locks and commits the atomic state object. This can be
+ * used in conjunction with the drm_atomic_helper_suspend() helper to
+ * implement suspend/resume for drivers that support atomic mode-setting.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ *
+ * See also:
+ * drm_atomic_helper_suspend()
+ */
+int drm_atomic_helper_resume(struct drm_device *dev,
+			     struct drm_atomic_state *state)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+	int err;
+
+	drm_mode_config_reset(dev);
+	drm_modeset_lock_all(dev);
+	state->acquire_ctx = config->acquire_ctx;
+	err = drm_atomic_commit(state);
+	drm_modeset_unlock_all(dev);
+
+	return err;
+}
+EXPORT_SYMBOL(drm_atomic_helper_resume);
+
+/**
  * drm_atomic_helper_crtc_set_property - helper for crtc properties
  * @crtc: DRM crtc
  * @property: DRM property
@@ -2472,7 +2627,9 @@ EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
  * @ctx: lock acquisition context
  *
  * Makes a copy of the current atomic state by looping over all objects and
- * duplicating their respective states.
+ * duplicating their respective states. This is used for example by suspend/
+ * resume support code to save the state prior to suspend such that it can
+ * be restored upon resume.
  *
  * Note that this treats atomic state as persistent between save and restore.
  * Drivers must make sure that this is possible and won't result in confusion
@@ -2484,6 +2641,9 @@ EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
  * Returns:
  * A pointer to the copy of the atomic state object on success or an
  * ERR_PTR()-encoded error code on failure.
+ *
+ * See also:
+ * drm_atomic_helper_suspend(), drm_atomic_helper_resume()
  */
 struct drm_atomic_state *
 drm_atomic_helper_duplicate_state(struct drm_device *dev,