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

[Maarten Lankhorst]

Op 29-06-17 om 12:31 schreef Daniel Vetter:
> On Thu, Jun 29, 2017 at 12:22 PM, Maarten Lankhorst
> <maarten.lankhorst at linux.intel.com> wrote:
>>> +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.
> I just blindly smashed the old fbdev code in with the helper and moved
> the locking out. Not sure what would be better here, since the
> continue is in a way just part of a non-existent
> drm_fb_helper_for_each_active_crtc loop iterator. Not sure it's worth
> it to overpolish this code to such an extent :-)
> -Daniel

Well checking for crtc_state->enable instead of mode_set.mode probably means we're at least bug for bug
compatible vs legacy. It might be better to add a bool active to restore_fbdev_mode_atomic.

What about something like this? The less atomic commits the better. :)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index e49bae10f0ee..2c401fe8531c 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -378,7 +378,7 @@ int drm_fb_helper_debug_leave(struct fb_info *info)
 }
 EXPORT_SYMBOL(drm_fb_helper_debug_leave);
 
-static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper)
+static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper, bool active)
 {
 	struct drm_device *dev = fb_helper->dev;
 	struct drm_plane *plane;
@@ -427,6 +427,17 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper)
 		ret = __drm_atomic_helper_set_config(mode_set, state);
 		if (ret != 0)
 			goto out_state;
+
+		/*
+		 * __drm_atomic_helper_set_config() sets active when a
+		 * mode is set, unconditionally clear it if we force DPMS off
+		 */
+		if (!active) {
+			struct drm_crtc *crtc = mode_set->crtc;
+			struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+
+			crtc_state->active = false;
+		}
 	}
 
 	ret = drm_atomic_commit(state);
@@ -497,7 +508,7 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
 	struct drm_device *dev = fb_helper->dev;
 
 	if (drm_drv_uses_atomic_modeset(dev))
-		return restore_fbdev_mode_atomic(fb_helper);
+		return restore_fbdev_mode_atomic(fb_helper, true);
 	else
 		return restore_fbdev_mode_legacy(fb_helper);
 }
@@ -714,7 +669,7 @@ static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
 	}
 
 	if (drm_drv_uses_atomic_modeset(fb_helper->dev))
-		dpms_atomic(fb_helper, dpms_mode);
+		restore_fbdev_mode_atomic(fb_helper, dpms_mode == DRM_MODE_DPMS_ON);
 	else
 		dpms_legacy(fb_helper, dpms_mode);
 	mutex_unlock(&fb_helper->lock);