drm: refcnt drm_framebuffer (v4.1)
This simplifies drm fb lifetime, and if the crtc/plane needs to hold a ref to the fb when disabling a pipe until the next vblank, this avoids the need to make disabling an overlay synchronous. This is a problem that shows up when userspace is using a drm plane to implement a hw cursor.. making overlay disable synchronous causes a performance problem when x11 is rapidly enabling/disabling the hw cursor. But not making it synchronous opens up a race condition for crashing if userspace turns around and immediately deletes the fb. Refcnt'ing the fb makes it possible to solve this problem. v1: original v2: add drm_framebuffer_remove() which is called in all paths where fb->funcs->destroy() was directly called before. This cleans up the CRTCs/planes that the fb was attached to. You should only directly use drm_framebuffer_unreference() if you are also using drm_framebuffer_reference() to keep a ref to the fb. v3: add comment explaining the fb refcount v4: remove duplicate 'list_del(&fb->filp_head)' [airlied: v4.1: fix local rejection] Signed-off-by: Rob Clark <rob@ti.com> Signed-off-by: Dave Airlie <airlied@redhat.com>
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33cce6e980
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f7eff60ea0
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@ -294,6 +294,8 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb,
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{
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int ret;
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kref_init(&fb->refcount);
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ret = drm_mode_object_get(dev, &fb->base, DRM_MODE_OBJECT_FB);
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if (ret)
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return ret;
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@ -307,6 +309,38 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb,
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}
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EXPORT_SYMBOL(drm_framebuffer_init);
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static void drm_framebuffer_free(struct kref *kref)
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{
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struct drm_framebuffer *fb =
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container_of(kref, struct drm_framebuffer, refcount);
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fb->funcs->destroy(fb);
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}
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/**
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* drm_framebuffer_unreference - unref a framebuffer
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*
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* LOCKING:
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* Caller must hold mode config lock.
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*/
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void drm_framebuffer_unreference(struct drm_framebuffer *fb)
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{
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struct drm_device *dev = fb->dev;
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DRM_DEBUG("FB ID: %d\n", fb->base.id);
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WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
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kref_put(&fb->refcount, drm_framebuffer_free);
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}
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EXPORT_SYMBOL(drm_framebuffer_unreference);
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/**
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* drm_framebuffer_reference - incr the fb refcnt
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*/
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void drm_framebuffer_reference(struct drm_framebuffer *fb)
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{
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DRM_DEBUG("FB ID: %d\n", fb->base.id);
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kref_get(&fb->refcount);
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}
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EXPORT_SYMBOL(drm_framebuffer_reference);
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/**
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* drm_framebuffer_cleanup - remove a framebuffer object
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* @fb: framebuffer to remove
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@ -318,6 +352,32 @@ EXPORT_SYMBOL(drm_framebuffer_init);
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* it, setting it to NULL.
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*/
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void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
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{
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struct drm_device *dev = fb->dev;
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/*
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* This could be moved to drm_framebuffer_remove(), but for
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* debugging is nice to keep around the list of fb's that are
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* no longer associated w/ a drm_file but are not unreferenced
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* yet. (i915 and omapdrm have debugfs files which will show
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* this.)
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*/
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drm_mode_object_put(dev, &fb->base);
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list_del(&fb->head);
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dev->mode_config.num_fb--;
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}
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EXPORT_SYMBOL(drm_framebuffer_cleanup);
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/**
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* drm_framebuffer_remove - remove and unreference a framebuffer object
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* @fb: framebuffer to remove
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*
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* LOCKING:
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* Caller must hold mode config lock.
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*
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* Scans all the CRTCs and planes in @dev's mode_config. If they're
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* using @fb, removes it, setting it to NULL.
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*/
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void drm_framebuffer_remove(struct drm_framebuffer *fb)
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{
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struct drm_device *dev = fb->dev;
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struct drm_crtc *crtc;
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@ -350,11 +410,11 @@ void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
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}
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}
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drm_mode_object_put(dev, &fb->base);
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list_del(&fb->head);
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dev->mode_config.num_fb--;
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list_del(&fb->filp_head);
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drm_framebuffer_unreference(fb);
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}
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EXPORT_SYMBOL(drm_framebuffer_cleanup);
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EXPORT_SYMBOL(drm_framebuffer_remove);
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/**
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* drm_crtc_init - Initialise a new CRTC object
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@ -1031,7 +1091,7 @@ void drm_mode_config_cleanup(struct drm_device *dev)
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}
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list_for_each_entry_safe(fb, fbt, &dev->mode_config.fb_list, head) {
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fb->funcs->destroy(fb);
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drm_framebuffer_remove(fb);
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}
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list_for_each_entry_safe(plane, plt, &dev->mode_config.plane_list,
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@ -2337,11 +2397,7 @@ int drm_mode_rmfb(struct drm_device *dev,
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goto out;
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}
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/* TODO release all crtc connected to the framebuffer */
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/* TODO unhock the destructor from the buffer object */
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list_del(&fb->filp_head);
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fb->funcs->destroy(fb);
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drm_framebuffer_remove(fb);
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out:
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mutex_unlock(&dev->mode_config.mutex);
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@ -2491,8 +2547,7 @@ void drm_fb_release(struct drm_file *priv)
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mutex_lock(&dev->mode_config.mutex);
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list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) {
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list_del(&fb->filp_head);
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fb->funcs->destroy(fb);
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drm_framebuffer_remove(fb);
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}
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mutex_unlock(&dev->mode_config.mutex);
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}
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@ -266,8 +266,8 @@ static void exynos_drm_fbdev_destroy(struct drm_device *dev,
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/* release drm framebuffer and real buffer */
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if (fb_helper->fb && fb_helper->fb->funcs) {
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fb = fb_helper->fb;
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if (fb && fb->funcs->destroy)
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fb->funcs->destroy(fb);
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if (fb)
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drm_framebuffer_remove(fb);
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}
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/* release linux framebuffer */
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@ -276,7 +276,7 @@ fail:
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if (fbi)
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framebuffer_release(fbi);
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if (fb)
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fb->funcs->destroy(fb);
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drm_framebuffer_remove(fb);
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}
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return ret;
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@ -401,7 +401,7 @@ void omap_fbdev_free(struct drm_device *dev)
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/* this will free the backing object */
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if (fbdev->fb)
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fbdev->fb->funcs->destroy(fbdev->fb);
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drm_framebuffer_remove(fbdev->fb);
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kfree(fbdev);
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@ -218,6 +218,7 @@ struct drm_display_info {
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};
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struct drm_framebuffer_funcs {
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/* note: use drm_framebuffer_remove() */
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void (*destroy)(struct drm_framebuffer *framebuffer);
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int (*create_handle)(struct drm_framebuffer *fb,
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struct drm_file *file_priv,
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@ -242,6 +243,16 @@ struct drm_framebuffer_funcs {
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struct drm_framebuffer {
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struct drm_device *dev;
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/*
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* Note that the fb is refcounted for the benefit of driver internals,
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* for example some hw, disabling a CRTC/plane is asynchronous, and
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* scanout does not actually complete until the next vblank. So some
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* cleanup (like releasing the reference(s) on the backing GEM bo(s))
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* should be deferred. In cases like this, the driver would like to
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* hold a ref to the fb even though it has already been removed from
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* userspace perspective.
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*/
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struct kref refcount;
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struct list_head head;
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struct drm_mode_object base;
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const struct drm_framebuffer_funcs *funcs;
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@ -919,6 +930,9 @@ extern void drm_framebuffer_set_object(struct drm_device *dev,
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extern int drm_framebuffer_init(struct drm_device *dev,
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struct drm_framebuffer *fb,
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const struct drm_framebuffer_funcs *funcs);
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extern void drm_framebuffer_unreference(struct drm_framebuffer *fb);
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extern void drm_framebuffer_reference(struct drm_framebuffer *fb);
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extern void drm_framebuffer_remove(struct drm_framebuffer *fb);
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extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
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extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);
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extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);
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