drm/fb-helper: Instanciate shadow FB if configured in device's mode_config

Generic framebuffer emulation uses a shadow buffer for framebuffers with
dirty() function. If drivers want to use the shadow FB without such a
function, they can now set prefer_shadow or prefer_shadow_fbdev in their
mode_config structures. The former flag is exported to userspace, the
latter flag is fbdev-only.

v3:
	* only schedule dirty worker if fbdev uses shadow fb
	* test shadow fb settings with boolean operators
	* use bool for struct drm_mode_config.prefer_shadow_fbdev
	* fix documentation comments

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/315834/

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 7ba6a02..a7ba5b4 100644 (file)
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -421,7 +421,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
                                return;
                        drm_fb_helper_dirty_blit_real(helper, &clip_copy);
                }
-               helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
+               if (helper->fb->funcs->dirty)
+                       helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
+                                                &clip_copy, 1);
 
                if (helper->buffer)
                        drm_client_buffer_vunmap(helper->buffer);
@@ -613,6 +615,16 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 }
 EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
 
+static bool drm_fbdev_use_shadow_fb(struct drm_fb_helper *fb_helper)
+{
+       struct drm_device *dev = fb_helper->dev;
+       struct drm_framebuffer *fb = fb_helper->fb;
+
+       return dev->mode_config.prefer_shadow_fbdev ||
+              dev->mode_config.prefer_shadow ||
+              fb->funcs->dirty;
+}
+
 static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
                                u32 width, u32 height)
 {
@@ -620,7 +632,7 @@ static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
        struct drm_clip_rect *clip = &helper->dirty_clip;
        unsigned long flags;
 
-       if (!helper->fb->funcs->dirty)
+       if (!drm_fbdev_use_shadow_fb(helper))
                return;
 
        spin_lock_irqsave(&helper->dirty_lock, flags);
@@ -2213,7 +2225,7 @@ int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
 
        drm_fb_helper_fill_info(fbi, fb_helper, sizes);
 
-       if (fb->funcs->dirty) {
+       if (drm_fbdev_use_shadow_fb(fb_helper)) {
                struct fb_ops *fbops;
                void *shadow;
 

diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 759d462..f57eea0 100644 (file)
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -853,6 +853,13 @@ struct drm_mode_config {
        uint32_t preferred_depth, prefer_shadow;
 
        /**
+        * @prefer_shadow_fbdev:
+        *
+        * Hint to framebuffer emulation to prefer shadow-fb rendering.
+        */
+       bool prefer_shadow_fbdev;
+
+       /**
         * @quirk_addfb_prefer_xbgr_30bpp:
         *
         * Special hack for legacy ADDFB to keep nouveau userspace happy. Should