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drm: refcnt drm_framebuffer (v4.1)

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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>
This commit is contained in:
Rob Clark
2012-09-05 21:48:38 +00:00
committed by Dave Airlie
parent 33cce6e980
commit f7eff60ea0
4 changed files with 85 additions and 16 deletions
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4
drivers/gpu/drm/exynos/exynos_drm_fbdev.c
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@@ -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 */