From 709ffd82fc6ff760dc3a7f71bdf26d78a8e3caf0 Mon Sep 17 00:00:00 2001 From: Russell King Date: Wed, 15 Jul 2015 18:09:38 +0100 Subject: [PATCH] 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: Russell King --- drivers/gpu/drm/armada/armada_crtc.c | 53 ++++++++++++---------------- 1 file changed, 23 insertions(+), 30 deletions(-) diff --git a/drivers/gpu/drm/armada/armada_crtc.c b/drivers/gpu/drm/armada/armada_crtc.c index 8c43ecc19c15..5d627646601e 100644 --- a/drivers/gpu/drm/armada/armada_crtc.c +++ b/drivers/gpu/drm/armada/armada_crtc.c @@ -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; -- 2.20.1