[PATCH 1/4] drm/i915: add msecs_to_jiffies_timeout to guarantee minimum duration

[Imre Deak <imre.deak@intel.com>]

We need this to avoid premature timeouts whenever scheduling a timeout
based on the current jiffies value. For an explanation see [1].
The following patches will take the helper into use.

Once the more generic solution proposed in the thread at [1] is accepted
this patch can be reverted while keeping the follow-up patches.

[1] http://marc.info/?l=linux-kernel&m=136854294730957&w=2

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 639ec0b..78b6c56 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1981,4 +1981,19 @@ static inline void __user *to_user_ptr(u64 address)
 	return (void __user *)(uintptr_t)address;
 }
 
+static inline unsigned long msecs_to_jiffies_timeout(const unsigned int m)
+{
+	unsigned long j = msecs_to_jiffies(m);
+
+	return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1);
+}
+
+static inline unsigned long
+timespec_to_jiffies_timeout(const struct timespec *value)
+{
+	unsigned long j = timespec_to_jiffies(value);
+
+	return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1);
+}
+
 #endif
-- 
1.8.1.2