linux-kernel - [PATCH] vmwgfx: use monotonic event timestamps

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Date:   Mon, 27 Nov 2017 12:16:19 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     VMware Graphics <linux-graphics-maintainer@...are.com>,
        Sinclair Yeh <syeh@...are.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Deepak Singh Rawat <drawat@...are.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Ravikant B Sharma <ravikant.s2@...sung.com>,
        Joe Perches <joe@...ches.com>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] vmwgfx: use monotonic event timestamps

DRM_VMW_EVENT_FENCE_SIGNALED (struct drm_vmw_event_fence) and
DRM_EVENT_VBLANK (struct drm_event_vblank) pass timestamps in 32-bit
seconds/microseconds format.

As of commit c61eef726a78 ("drm: add support for monotonic vblank
timestamps"), other DRM drivers use monotonic times for drm_event_vblank,
but vmwgfx still uses CLOCK_REALTIME for both events, which suffers from
the y2038/y2106 overflow as well as time jumps.

For consistency, this changes vmwgfx to use ktime_get_ts64 as well,
which solves those problems and avoids the deprecated do_gettimeofday()
function.

This should be transparent to to user space, as long as it doesn't
compare the time against the result of gettimeofday().

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index d6b1c509ae01..55214d0da66e 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -897,11 +897,12 @@ static void vmw_event_fence_action_seq_passed(struct vmw_fence_action *action)
 	spin_lock_irq(&dev->event_lock);

 	if (likely(eaction->tv_sec != NULL)) {
-		struct timeval tv;
+		struct timespec64 ts;

-		do_gettimeofday(&tv);
-		*eaction->tv_sec = tv.tv_sec;
-		*eaction->tv_usec = tv.tv_usec;
+		ktime_get_ts64(&ts);
+		/* monotonic time, so no y2038 overflow */
+		*eaction->tv_sec = ts.tv_sec;
+		*eaction->tv_usec = ts.tv_nsec / NSEC_PER_USEC;
 	}

 	drm_send_event_locked(dev, eaction->event);
-- 
2.9.0