From d4055a9b207966ab4058550d818532b979d8bf78 Mon Sep 17 00:00:00 2001 From: Matthew Auld Date: Tue, 10 May 2016 15:21:28 +0100 Subject: drm: use seqlock for vblank time/count This patch aims to replace the roll-your-own seqlock implementation with full-blown seqlock'. We also remove the timestamp ring-buffer in favour of single timestamp/count pair protected by a seqlock. In turn this means we can now increment the vblank freely without the need for clamping. v2: - reduce the scope of the seqlock, keeping vblank_time_lock - make the seqlock per vblank_crtc, so multiple readers aren't blocked by the writer Cc: Mario Kleiner Cc: Daniel Vetter Cc: Ville Syrjälä Signed-off-by: Matthew Auld Reviewed-by: Ville Syrjälä Reviewed-by: Mario Kleiner Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1462890088-18194-1-git-send-email-matthew.auld@intel.com --- include/drm/drmP.h | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) (limited to 'include/drm') diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 84f1a8eefbdb..af8b71b2e5bd 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -52,6 +52,7 @@ #include #include #include +#include #include #include #include @@ -392,11 +393,6 @@ struct drm_master { void *driver_priv; }; -/* Size of ringbuffer for vblank timestamps. Just double-buffer - * in initial implementation. - */ -#define DRM_VBLANKTIME_RBSIZE 2 - /* Flags and return codes for get_vblank_timestamp() driver function. */ #define DRM_CALLED_FROM_VBLIRQ 1 #define DRM_VBLANKTIME_SCANOUTPOS_METHOD (1 << 0) @@ -725,10 +721,10 @@ struct drm_vblank_crtc { wait_queue_head_t queue; /**< VBLANK wait queue */ struct timer_list disable_timer; /* delayed disable timer */ - /* vblank counter, protected by dev->vblank_time_lock for writes */ - u32 count; - /* vblank timestamps, protected by dev->vblank_time_lock for writes */ - struct timeval time[DRM_VBLANKTIME_RBSIZE]; + seqlock_t seqlock; /* protects vblank count and time */ + + u32 count; /* vblank counter */ + struct timeval time; /* vblank timestamp */ atomic_t refcount; /* number of users of vblank interruptsper crtc */ u32 last; /* protected by dev->vbl_lock, used */ -- cgit v1.2.3-55-g7522