From 66377efa3fd468283a092f17692e81c2344b03ed Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Wed, 15 Jul 2015 18:11:24 +0100
Subject: [PATCH] drm/armada: use xchg() to atomically update dplane->old_fb
Rather than using a spinlock, use xchg() to atomically update
dplane->old_fb. This allows us to eliminate dplane->lock.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/gpu/drm/armada/armada_overlay.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/armada/armada_overlay.c b/drivers/gpu/drm/armada/armada_overlay.c
index 093c2d4f2b79..5e2dcecbf6ef 100644
--- a/drivers/gpu/drm/armada/armada_overlay.c
+++ b/drivers/gpu/drm/armada/armada_overlay.c
@@ -31,7 +31,6 @@ struct armada_ovl_plane_properties {
struct armada_ovl_plane {
struct drm_plane base;
- spinlock_t lock;
struct drm_framebuffer *old_fb;
uint32_t src_hw;
uint32_t dst_hw;
@@ -76,10 +75,7 @@ static void armada_ovl_retire_fb(struct armada_ovl_plane *dplane,
{
struct drm_framebuffer *old_fb;
- spin_lock(&dplane->lock);
- old_fb = dplane->old_fb;
- dplane->old_fb = fb;
- spin_unlock(&dplane->lock);
+ old_fb = xchg(&dplane->old_fb, fb);
if (old_fb)
armada_drm_queue_unref_work(dplane->base.dev, old_fb);
@@ -289,10 +285,7 @@ static int armada_ovl_plane_disable(struct drm_plane *plane)
if (plane->fb)
drm_framebuffer_unreference(plane->fb);
- spin_lock_irq(&dplane->lock);
- fb = dplane->old_fb;
- dplane->old_fb = NULL;
- spin_unlock_irq(&dplane->lock);
+ fb = xchg(&dplane->old_fb, NULL);
if (fb)
drm_framebuffer_unreference(fb);
@@ -464,7 +457,6 @@ int armada_overlay_plane_create(struct drm_device *dev, unsigned long crtcs)
if (!dplane)
return -ENOMEM;
- spin_lock_init(&dplane->lock);
init_waitqueue_head(&dplane->vbl.wait);
armada_drm_vbl_event_init(&dplane->vbl.update, armada_ovl_plane_vbl,
dplane);