[Intel-gfx] [PATCH 1/5] drm: Add atomic helper to redo a modeset on current mode

[Daniel Vetter]

On Fri, Oct 21, 2016 at 04:45:39PM -0700, Manasi Navare wrote:
> This function provides a way for the driver to redo a
> modeset on the current mode and retry the link training
> at a lower link rate/lane count/bpp. This will get called
> incase the link training fails during the current modeset.
> 
> Cc: dri-devel at lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 58 +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_atomic_helper.h     |  1 +
>  2 files changed, 59 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index f936276..0c1614e 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2895,6 +2895,64 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
>  EXPORT_SYMBOL(drm_atomic_helper_connector_dpms);
>  
>  /**
> + * drm_atomic_helper_connector_modeset - Force a modeset on a connector
> + * @connector: DRM connector
> + *
> + * Provides a way to redo a modeset with the current mode so that it can
> + * drop the bpp, link rate/lane count and retry the link training.
> + *
> + * Returns:
> + * Returns 0 on success, negative errno numbers on failure.
> + */
> +int
> +drm_atomic_helper_connector_modeset(struct drm_connector *connector)
> +{
> +	struct drm_device *dev = connector->dev;
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct drm_atomic_state *state;
> +	struct drm_connector_state *connector_state;
> +	struct drm_crtc_state *crtc_state;
> +	int ret = 0;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +	state = drm_atomic_state_alloc(dev);
> +	if (!state) {
> +		ret = -ENOMEM;
> +		goto fail;
> +	}
> +	state->acquire_ctx = &ctx;
> +retry:
> +	ret = 0;
> +	connector_state = drm_atomic_get_connector_state(state, connector);
> +	if (IS_ERR(connector_state)) {
> +		ret = PTR_ERR(connector_state);
> +		goto fail;
> +	}
> +	if (!connector_state->crtc)
> +		goto fail;
> +
> +	crtc_state = drm_atomic_get_existing_crtc_state(state,
> +							connector_state->crtc);
> +	crtc_state->connectors_changed = true;

This line here only works if the driver uses the helpers for checking and
commit, and when it doesn't overwrite connectors_changed. I think the
kerneldoc should mention this.

The other issue: You cannot call this from modeset code itself because of
recursion. I think this also must be mentioned.
-Daniel

> +	ret = drm_atomic_commit(state);
> +fail:
> +	if (ret == -EDEADLK) {
> +		drm_atomic_state_clear(state);
> +		drm_modeset_backoff(&ctx);
> +		goto retry;
> +	}
> +
> +	if (state)
> +		drm_atomic_state_put(state);
> +
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_connector_modeset);
> +
> +/**
>   * drm_atomic_helper_best_encoder - Helper for &drm_connector_helper_funcs
>   *                                  ->best_encoder callback
>   * @connector: Connector control structure
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index 7ff92b0..8de24dc 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -126,6 +126,7 @@ int drm_atomic_helper_page_flip(struct drm_crtc *crtc,
>  				uint32_t flags);
>  int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
>  				     int mode);
> +int drm_atomic_helper_connector_modeset(struct drm_connector *connector);
>  struct drm_encoder *
>  drm_atomic_helper_best_encoder(struct drm_connector *connector);
>  
> -- 
> 1.9.1
> 
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> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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