Re: [PATCH 09/13] drm/fb-helper: Split dpms handling into legacy and atomic paths

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 27-06-17 om 16:59 schreef Daniel Vetter:
> Like with panning and modesetting, and like with those, stick with
> simple drm_modeset_locking_all for the legacy path, and the full
> atomic dance for atomic drivers.
>
> This means a bit more boilerplate since setting up the atomic state
> machinery is rather verbose, but then this is shared code for 30+
> drivers or so, so meh.
>
> After this patch there's only the LUT/cmap path which is still using
> drm_modeset_lock_all for an atomic driver. But Peter is already
> locking into reworking that, so I'll leave that code as-is for now.
>
> Cc: Peter Rosin <peda@axentia.se>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 88 +++++++++++++++++++++++++++++++++++------
>  1 file changed, 76 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 59e2916471b2..bbd4c6d0378d 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -616,23 +616,13 @@ static struct sysrq_key_op sysrq_drm_fb_helper_restore_op = {
>  static struct sysrq_key_op sysrq_drm_fb_helper_restore_op = { };
>  #endif
>  
> -static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
> +static void dpms_legacy(struct drm_fb_helper *fb_helper, int dpms_mode)
>  {
> -	struct drm_fb_helper *fb_helper = info->par;
>  	struct drm_device *dev = fb_helper->dev;
>  	struct drm_crtc *crtc;
>  	struct drm_connector *connector;
>  	int i, j;
>  
> -	/*
> -	 * For each CRTC in this fb, turn the connectors on/off.
> -	 */
> -	mutex_lock(&fb_helper->lock);
> -	if (!drm_fb_helper_is_bound(fb_helper)) {
> -		mutex_unlock(&fb_helper->lock);
> -		return;
> -	}
> -
>  	drm_modeset_lock_all(dev);
>  	for (i = 0; i < fb_helper->crtc_count; i++) {
>  		crtc = fb_helper->crtc_info[i].mode_set.crtc;
> @@ -649,6 +639,81 @@ static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
>  		}
>  	}
>  	drm_modeset_unlock_all(dev);
> +}
> +
> +static void dpms_atomic(struct drm_fb_helper *fb_helper, int dpms_mode)
> +{
> +	struct drm_device *dev = fb_helper->dev;
> +	struct drm_atomic_state *state;
> +	int i, ret;
> +
> +	struct drm_modeset_acquire_ctx ctx;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +
> +	state = drm_atomic_state_alloc(dev);
> +	if (!state) {
> +		ret = -ENOMEM;
> +		goto out_ctx;
> +	}
> +
> +	state->acquire_ctx = &ctx;
> +retry:
> +	for (i = 0; i < fb_helper->crtc_count; i++) {
> +		struct drm_crtc_state *crtc_state;
> +		struct drm_crtc *crtc;
> +
> +		if (!fb_helper->crtc_info[i].mode_set.mode)
> +			continue;
> +
> +		crtc = fb_helper->crtc_info[i].mode_set.crtc;
> +
> +		crtc_state = drm_atomic_get_crtc_state(state, crtc);
> +		if (IS_ERR(crtc_state)) {
> +			ret = PTR_ERR(crtc_state);
> +			goto out_state;
> +		}
Hm, maybe remove the early continue, and change this to if (crtc_state->enable) crtc_state->active = ...; ?

I don't know if it matters in practice, but it might be more resilient when crtc state does not match our expected state,
similar to how DPMS on is ignored without CRTC.
> +		crtc_state->active = dpms_mode == DRM_MODE_DPMS_ON;
> +	}
> +
> +	ret = drm_atomic_commit(state);
> +out_state:
> +	if (ret == -EDEADLK)
> +		goto backoff;
> +
> +	drm_atomic_state_put(state);
> +out_ctx:
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
> +
> +	return;
> +
> +backoff:
> +	drm_atomic_state_clear(state);
> +	drm_modeset_backoff(&ctx);
> +
> +	goto retry;
> +
> +}
> +
> +static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +
> +	/*
> +	 * For each CRTC in this fb, turn the connectors on/off.
> +	 */
> +	mutex_lock(&fb_helper->lock);
> +	if (!drm_fb_helper_is_bound(fb_helper)) {
> +		mutex_unlock(&fb_helper->lock);
> +		return;
> +	}
> +
> +	if (drm_drv_uses_atomic_modeset(fb_helper->dev))
> +		dpms_atomic(fb_helper, dpms_mode);
> +	else
> +		dpms_legacy(fb_helper, dpms_mode);
>  	mutex_unlock(&fb_helper->lock);
>  }
>  
> @@ -2467,7 +2532,6 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config);
>   */
>  int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>  {
> -	struct drm_device *dev = fb_helper->dev;
>  	int err = 0;
>  
>  	if (!drm_fbdev_emulation)


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