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

[Maarten Lankhorst]

Op 29-06-17 om 13:00 schreef Daniel Vetter:
> On Thu, Jun 29, 2017 at 12:58 PM, Maarten Lankhorst
> <maarten.lankhorst at linux.intel.com> wrote:
>> 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. :)
> Hm yeah, that sounds like a useful simplification. I don't think we
> should do too much into extremes in fbdev and only have 1 atomic
> commit, because fbdev fundamentally isn't atomic. But merging them
> where it makes sense is reasonable.
> -Daniel

Agreed, perhaps with pan_display_atomic too, if we no longer use modeset locks,
then it becomes very simple..
What about getting rid of that one too, in favor of this?

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 0cd2035ac1d1..b4356fdf5e6d 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1557,70 +1557,36 @@ int drm_fb_helper_set_par(struct fb_info *info)
 }
 EXPORT_SYMBOL(drm_fb_helper_set_par);
 
-static int pan_display_atomic(struct fb_var_screeninfo *var,
-			      struct fb_info *info)
+static void pan_set(struct drm_fb_helper *fb_helper, int x, int y)
 {
-	struct drm_fb_helper *fb_helper = info->par;
-	struct drm_device *dev = fb_helper->dev;
-	struct drm_atomic_state *state;
-	struct drm_plane *plane;
-	int i, ret;
-	unsigned int plane_mask;
-	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;
-	}
+	int i;
 
-	state->acquire_ctx = &ctx;
-retry:
-	plane_mask = 0;
 	for (i = 0; i < fb_helper->crtc_count; i++) {
 		struct drm_mode_set *mode_set;
 
 		mode_set = &fb_helper->crtc_info[i].mode_set;
 
-		mode_set->x = var->xoffset;
-		mode_set->y = var->yoffset;
-
-		ret = __drm_atomic_helper_set_config(mode_set, state);
-		if (ret != 0)
-			goto out_state;
-
-		plane = mode_set->crtc->primary;
-		plane_mask |= (1 << drm_plane_index(plane));
-		plane->old_fb = plane->fb;
+		mode_set->x = x;
+		mode_set->y = y;
 	}
+}
 
-	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto out_state;
-
-	info->var.xoffset = var->xoffset;
-	info->var.yoffset = var->yoffset;
+static int pan_display_atomic(struct fb_var_screeninfo *var,
+			      struct fb_info *info)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	int ret;
 
-out_state:
-	drm_atomic_clean_old_fb(dev, plane_mask, ret);
+	pan_set(fb_helper, var->xoffset, var->yoffset);
 
-	if (ret == -EDEADLK)
-		goto backoff;
-
-	drm_atomic_state_put(state);
-out_ctx:
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
+	ret = restore_fbdev_mode(fb_helper);
+	if (!ret) {
+		info->var.xoffset = var->xoffset;
+		info->var.yoffset = var->yoffset;
+	} else
+		pan_set(fb_helper, info->var.xoffset, info->var.yoffset);
 
 	return ret;
-
-backoff:
-	drm_atomic_state_clear(state);
-	drm_modeset_backoff(&ctx);
-
-	goto retry;
 }
 
 static int pan_display_legacy(struct fb_var_screeninfo *var,