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Commit f7eff60e authored by Rob Clark's avatar Rob Clark Committed by Dave Airlie
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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: default avatarRob Clark <rob@ti.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 33cce6e9

drivers/gpu/drm/drm_crtc.c

+67 −12
Original line number Diff line number Diff line
@@ -294,6 +294,8 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb, 
{

	int ret;



	kref_init(&fb->refcount);



	ret = drm_mode_object_get(dev, &fb->base, DRM_MODE_OBJECT_FB);

	if (ret)

		return ret;
@@ -307,6 +309,38 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb, 
}

EXPORT_SYMBOL(drm_framebuffer_init);



static void drm_framebuffer_free(struct kref *kref)

{

	struct drm_framebuffer *fb =

			container_of(kref, struct drm_framebuffer, refcount);

	fb->funcs->destroy(fb);

}



/**

 * drm_framebuffer_unreference - unref a framebuffer

 *

 * LOCKING:

 * Caller must hold mode config lock.

 */

void drm_framebuffer_unreference(struct drm_framebuffer *fb)

{

	struct drm_device *dev = fb->dev;

	DRM_DEBUG("FB ID: %d\n", fb->base.id);

	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

	kref_put(&fb->refcount, drm_framebuffer_free);

}

EXPORT_SYMBOL(drm_framebuffer_unreference);



/**

 * drm_framebuffer_reference - incr the fb refcnt

 */

void drm_framebuffer_reference(struct drm_framebuffer *fb)

{

	DRM_DEBUG("FB ID: %d\n", fb->base.id);

	kref_get(&fb->refcount);

}

EXPORT_SYMBOL(drm_framebuffer_reference);



/**

 * drm_framebuffer_cleanup - remove a framebuffer object

 * @fb: framebuffer to remove
@@ -318,6 +352,32 @@ EXPORT_SYMBOL(drm_framebuffer_init); 
 * it, setting it to NULL.

 */

void drm_framebuffer_cleanup(struct drm_framebuffer *fb)

{

	struct drm_device *dev = fb->dev;

	/*

	 * This could be moved to drm_framebuffer_remove(), but for

	 * debugging is nice to keep around the list of fb's that are

	 * no longer associated w/ a drm_file but are not unreferenced

	 * yet.  (i915 and omapdrm have debugfs files which will show

	 * this.)

	 */

	drm_mode_object_put(dev, &fb->base);

	list_del(&fb->head);

	dev->mode_config.num_fb--;

}

EXPORT_SYMBOL(drm_framebuffer_cleanup);



/**

 * drm_framebuffer_remove - remove and unreference a framebuffer object

 * @fb: framebuffer to remove

 *

 * LOCKING:

 * Caller must hold mode config lock.

 *

 * Scans all the CRTCs and planes in @dev's mode_config.  If they're

 * using @fb, removes it, setting it to NULL.

 */

void drm_framebuffer_remove(struct drm_framebuffer *fb)

{

	struct drm_device *dev = fb->dev;

	struct drm_crtc *crtc;
@@ -350,11 +410,11 @@ void drm_framebuffer_cleanup(struct drm_framebuffer *fb) 
		}

	}



	drm_mode_object_put(dev, &fb->base);

	list_del(&fb->head);

	dev->mode_config.num_fb--;

	list_del(&fb->filp_head);



	drm_framebuffer_unreference(fb);

}

EXPORT_SYMBOL(drm_framebuffer_cleanup);

EXPORT_SYMBOL(drm_framebuffer_remove);



/**

 * drm_crtc_init - Initialise a new CRTC object
@@ -1031,7 +1091,7 @@ void drm_mode_config_cleanup(struct drm_device *dev) 
	}



	list_for_each_entry_safe(fb, fbt, &dev->mode_config.fb_list, head) {

		fb->funcs->destroy(fb);

		drm_framebuffer_remove(fb);

	}



	list_for_each_entry_safe(plane, plt, &dev->mode_config.plane_list,
@@ -2337,11 +2397,7 @@ int drm_mode_rmfb(struct drm_device *dev, 
		goto out;

	}



	/* TODO release all crtc connected to the framebuffer */

	/* TODO unhock the destructor from the buffer object */



	list_del(&fb->filp_head);

	fb->funcs->destroy(fb);

	drm_framebuffer_remove(fb);



out:

	mutex_unlock(&dev->mode_config.mutex);
@@ -2491,8 +2547,7 @@ void drm_fb_release(struct drm_file *priv) 


	mutex_lock(&dev->mode_config.mutex);

	list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) {

		list_del(&fb->filp_head);

		fb->funcs->destroy(fb);

		drm_framebuffer_remove(fb);

	}

	mutex_unlock(&dev->mode_config.mutex);

}

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

+2 −2
Original line number Diff line number Diff line
@@ -266,8 +266,8 @@ static void exynos_drm_fbdev_destroy(struct drm_device *dev, 
	/* release drm framebuffer and real buffer */

	if (fb_helper->fb && fb_helper->fb->funcs) {

		fb = fb_helper->fb;

		if (fb && fb->funcs->destroy)

			fb->funcs->destroy(fb);

		if (fb)

			drm_framebuffer_remove(fb);

	}



	/* release linux framebuffer */

drivers/staging/omapdrm/omap_fbdev.c

+2 −2
Original line number Diff line number Diff line
@@ -276,7 +276,7 @@ fail: 
		if (fbi)

			framebuffer_release(fbi);

		if (fb)

			fb->funcs->destroy(fb);

			drm_framebuffer_remove(fb);

	}



	return ret;
@@ -401,7 +401,7 @@ void omap_fbdev_free(struct drm_device *dev) 


	/* this will free the backing object */

	if (fbdev->fb)

		fbdev->fb->funcs->destroy(fbdev->fb);

		drm_framebuffer_remove(fbdev->fb);



	kfree(fbdev);

include/drm/drm_crtc.h

+14 −0
Original line number Diff line number Diff line
@@ -218,6 +218,7 @@ struct drm_display_info { 
};



struct drm_framebuffer_funcs {

	/* note: use drm_framebuffer_remove() */

	void (*destroy)(struct drm_framebuffer *framebuffer);

	int (*create_handle)(struct drm_framebuffer *fb,

			     struct drm_file *file_priv,
@@ -242,6 +243,16 @@ struct drm_framebuffer_funcs { 


struct drm_framebuffer {

	struct drm_device *dev;

	/*

	 * Note that the fb is refcounted for the benefit of driver internals,

	 * for example some hw, disabling a CRTC/plane is asynchronous, and

	 * scanout does not actually complete until the next vblank.  So some

	 * cleanup (like releasing the reference(s) on the backing GEM bo(s))

	 * should be deferred.  In cases like this, the driver would like to

	 * hold a ref to the fb even though it has already been removed from

	 * userspace perspective.

	 */

	struct kref refcount;

	struct list_head head;

	struct drm_mode_object base;

	const struct drm_framebuffer_funcs *funcs;
@@ -919,6 +930,9 @@ extern void drm_framebuffer_set_object(struct drm_device *dev, 
extern int drm_framebuffer_init(struct drm_device *dev,

				struct drm_framebuffer *fb,

				const struct drm_framebuffer_funcs *funcs);

extern void drm_framebuffer_unreference(struct drm_framebuffer *fb);

extern void drm_framebuffer_reference(struct drm_framebuffer *fb);

extern void drm_framebuffer_remove(struct drm_framebuffer *fb);

extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);

extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);

extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);