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Commit 709ffd82 authored by Russell King's avatar Russell King
Browse files

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



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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent e0ac5e9b

drivers/gpu/drm/armada/armada_crtc.c

+23 −30
Original line number Diff line number Diff line
@@ -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;