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

[Daniel Vetter]

On Wed, Aug 12, 2015 at 04:37:29PM +0200, Thierry Reding wrote:
> 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().

I think an analog paragraph should be added to duplicate_state(), maybe in
this patch?

> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.

Please add the same caveat about locking like for duplicate_state here.

> + */
> +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;

Same comment about reusing the hidden acquire_ctx: Please don't and
instead make it an explicit paramter.

> +
> +	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.

I'd mention the two helpers explicitly so that they all get linked up here
in the kerneldoc (i.e. duplicate_state() and disable_all()).

lgtm otherwise.
-Daniel

> + *
> + * 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
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch