[PATCH] drm/i915: compute wait_ioctl timeout correctly

[Daniel Vetter <daniel.vetter@ffwll.ch>]

We've lost the +1 required for correct timeouts in

commit 5ed0bdf21a85d78e04f89f15ccf227562177cbd9
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Wed Jul 16 21:05:06 2014 +0000

    drm: i915: Use nsec based interfaces

    Use ktime_get_raw_ns() and get rid of the back and forth timespec
    conversions.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: John Stultz <john.stultz@linaro.org>

So fix this up by reinstating our handrolled _timeout function. While
at it bother with handling MAX_JIFFIES.

v2: Convert to usecs (we don't care about the accuracy anyway) first
to avoid overflow issues Dave Gordon spotted.

Cc: Dave Gordon <david.s.gordon@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82749
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 11 +++++++++++
 drivers/gpu/drm/i915/i915_gem.c |  3 ++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 049482f5d9ac..ef1f00e0a7b3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3097,6 +3097,17 @@ static inline unsigned long msecs_to_jiffies_timeout(const unsigned int m)
 	return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1);
 }
 
+static inline unsigned long nsecs_to_jiffies_timeout(const u64 m)
+{
+	u64 usecs = div_u64(m + 999, 1000);
+	unsigned long j = usecs_to_jiffies(usecs);
+
+	if (usecs > (u64)jiffies_to_usecs(MAX_JIFFY_OFFSET))
+		return MAX_JIFFY_OFFSET;
+
+	return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1);
+}
+
 static inline unsigned long
 timespec_to_jiffies_timeout(const struct timespec *value)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9d362d320d82..04a9f26407ae 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1226,7 +1226,8 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
 	if (i915_gem_request_completed(req, true))
 		return 0;
 
-	timeout_expire = timeout ? jiffies + nsecs_to_jiffies((u64)*timeout) : 0;
+	timeout_expire = timeout ?
+		jiffies + nsecs_to_jiffies_timeout((u64)*timeout) : 0;
 
 	if (INTEL_INFO(dev)->gen >= 6 && ring->id == RCS && can_wait_boost(file_priv)) {
 		gen6_rps_boost(dev_priv);
-- 
1.9.3