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drm/armada: redo locking and atomics for armada_drm_crtc_complete_frame_work()

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We can do better with armada_drm_crtc_complete_frame_work() - we can
avoid taking the event lock unless a call to drm_send_vblank_event()
is required, and using cmpxchg() and xchg(), we can eliminate the
locking around dcrtc->frame_work entirely.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-07-15 18:09:38 +01:00
parent e0ac5e9b4b
commit 709ffd82fc
1 changed files with 23 additions and 30 deletions
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53
drivers/gpu/drm/armada/armada_crtc.c
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@ -215,7 +215,6 @@ static int armada_drm_crtc_queue_frame_work(struct armada_crtc *dcrtc,
struct armada_frame_work *work)
{
struct drm_device *dev = dcrtc->crtc.dev;
unsigned long flags;
int ret;
ret = drm_vblank_get(dev, dcrtc->num);
@ -224,30 +223,29 @@ static int armada_drm_crtc_queue_frame_work(struct armada_crtc *dcrtc,
return ret;
}
spin_lock_irqsave(&dev->event_lock, flags);
if (!dcrtc->frame_work)
dcrtc->frame_work = work;
else
ret = -EBUSY;
spin_unlock_irqrestore(&dev->event_lock, flags);
if (ret)
if (cmpxchg(&dcrtc->frame_work, NULL, work)) {
drm_vblank_put(dev, dcrtc->num);
ret = -EBUSY;
}
return ret;
}
static void armada_drm_crtc_complete_frame_work(struct armada_crtc *dcrtc)
static void armada_drm_crtc_complete_frame_work(struct armada_crtc *dcrtc,
struct armada_frame_work *work)
{
struct drm_device *dev = dcrtc->crtc.dev;
struct armada_frame_work *work = dcrtc->frame_work;
dcrtc->frame_work = NULL;
unsigned long flags;
spin_lock_irqsave(&dcrtc->irq_lock, flags);
armada_drm_crtc_update_regs(dcrtc, work->regs);
spin_unlock_irqrestore(&dcrtc->irq_lock, flags);
if (work->event)
if (work->event) {
spin_lock_irqsave(&dev->event_lock, flags);
drm_send_vblank_event(dev, dcrtc->num, work->event);
spin_unlock_irqrestore(&dev->event_lock, flags);
}
drm_vblank_put(dev, dcrtc->num);
@ -293,7 +291,7 @@ static void armada_drm_crtc_finish_fb(struct armada_crtc *dcrtc,
static void armada_drm_vblank_off(struct armada_crtc *dcrtc)
{
struct drm_device *dev = dcrtc->crtc.dev;
struct armada_frame_work *work;
/*
* Tell the DRM core that vblank IRQs aren't going to happen for
@ -302,10 +300,9 @@ static void armada_drm_vblank_off(struct armada_crtc *dcrtc)
drm_crtc_vblank_off(&dcrtc->crtc);
/* Handle any pending flip event. */
spin_lock_irq(&dev->event_lock);
if (dcrtc->frame_work)
armada_drm_crtc_complete_frame_work(dcrtc);
spin_unlock_irq(&dev->event_lock);
work = xchg(&dcrtc->frame_work, NULL);
if (work)
armada_drm_crtc_complete_frame_work(dcrtc, work);
}
void armada_drm_crtc_gamma_set(struct drm_crtc *crtc, u16 r, u16 g, u16 b,
@ -434,12 +431,10 @@ static void armada_drm_crtc_irq(struct armada_crtc *dcrtc, u32 stat)
spin_unlock(&dcrtc->irq_lock);
if (stat & GRA_FRAME_IRQ) {
struct drm_device *dev = dcrtc->crtc.dev;
struct armada_frame_work *work = xchg(&dcrtc->frame_work, NULL);
spin_lock(&dev->event_lock);
if (dcrtc->frame_work)
armada_drm_crtc_complete_frame_work(dcrtc);
spin_unlock(&dev->event_lock);
if (work)
armada_drm_crtc_complete_frame_work(dcrtc, work);
wake_up(&dcrtc->frame_wait);
}
@ -957,8 +952,6 @@ static int armada_drm_crtc_page_flip(struct drm_crtc *crtc,
{
struct armada_crtc *dcrtc = drm_to_armada_crtc(crtc);
struct armada_frame_work *work;
struct drm_device *dev = crtc->dev;
unsigned long flags;
unsigned i;
int ret;
@ -1004,10 +997,10 @@ static int armada_drm_crtc_page_flip(struct drm_crtc *crtc,
* interrupt, so complete it now.
*/
if (dpms_blanked(dcrtc->dpms)) {
spin_lock_irqsave(&dev->event_lock, flags);
if (dcrtc->frame_work)
armada_drm_crtc_complete_frame_work(dcrtc);
spin_unlock_irqrestore(&dev->event_lock, flags);
struct armada_frame_work *work = xchg(&dcrtc->frame_work, NULL);
if (work)
armada_drm_crtc_complete_frame_work(dcrtc, work);
}
return 0;