[PATCH v2 2/3] drm/atomic-helper: Implement subsystem-level suspend/resume

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

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

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 141 ++++++++++++++++++++++++++++++++++++
 include/drm/drm_atomic_helper.h     |   5 ++
 2 files changed, 146 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 1f84df3b0a5d..0eb45a7a760e 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1751,6 +1751,147 @@ backoff:
 EXPORT_SYMBOL(drm_atomic_helper_set_config);
 
 /**
+ * drm_atomic_helper_disable_all - disable all currently active outputs
+ * @dev: DRM device
+ *
+ * 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. See drm_atomic_helper_suspend().
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_atomic_helper_disable_all(struct drm_device *dev)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+	struct drm_connector_state *conn_state;
+	struct drm_atomic_state *state;
+	struct drm_connector *conn;
+	unsigned int i;
+	int err;
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state)
+		return -ENOMEM;
+
+	state->acquire_ctx = config->acquire_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;
+		}
+
+		err = drm_atomic_add_affected_connectors(state, crtc);
+		if (err < 0)
+			goto free;
+
+		conn->dpms = DRM_MODE_DPMS_OFF;
+		crtc_state->active = false;
+	}
+
+	err = drm_atomic_commit(state);
+	if (err < 0) {
+		/* restore DPMS mode */
+		for_each_connector_in_state(state, conn, conn_state, i)
+			conn->dpms = DRM_MODE_DPMS_ON;
+
+		goto free;
+	}
+
+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.
+ */
+struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev)
+{
+	struct drm_atomic_state *state;
+	int err;
+
+	drm_modeset_lock_all(dev);
+
+	state = drm_atomic_helper_duplicate_state(dev);
+	if (IS_ERR(state))
+		goto unlock;
+
+	err = drm_atomic_helper_disable_all(dev);
+	if (err < 0) {
+		drm_atomic_state_free(state);
+		state = ERR_PTR(err);
+		goto unlock;
+	}
+
+unlock:
+	drm_modeset_unlock_all(dev);
+	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.
+ */
+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
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 5d27612997ce..080f131c9f2e 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -75,6 +75,11 @@ int drm_atomic_helper_update_plane(struct drm_plane *plane,
 int drm_atomic_helper_disable_plane(struct drm_plane *plane);
 int drm_atomic_helper_set_config(struct drm_mode_set *set);
 
+int drm_atomic_helper_disable_all(struct drm_device *dev);
+struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev);
+int drm_atomic_helper_resume(struct drm_device *dev,
+			     struct drm_atomic_state *state);
+
 int drm_atomic_helper_crtc_set_property(struct drm_crtc *crtc,
 					struct drm_property *property,
 					uint64_t val);
-- 
2.4.5