drm/i915: Inifite timeout for wait ioctl

Change the ns_timeout parameter of the wait ioctl to a signed value.
Doing this allows the kernel to provide an infinite wait when a timeout
of less than 0 is provided. This mimics select/poll.

Initially the parameter was meant to match up with the GL spec 1:1, but
after being made aware of how much 2^64 - 1 nanoseconds actually is, I
do not think anyone will ever notice the loss of 1 bit.

The infinite timeout on waiting is similar to the existing i915
userspace interface with the exception that struct_mutex is dropped
while doing the wait in this ioctl.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index af67803e635f..deaa0d4bb456 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2082,11 +2082,14 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
         struct drm_i915_gem_wait *args = data;
         struct drm_i915_gem_object *obj;
         struct intel_ring_buffer *ring = NULL;
-        struct timespec timeout;
+        struct timespec timeout_stack, *timeout = NULL;
         u32 seqno = 0;
         int ret = 0;
 
-        timeout = ns_to_timespec(args->timeout_ns);
+        if (args->timeout_ns >= 0) {
+                timeout_stack = ns_to_timespec(args->timeout_ns);
+                timeout = &timeout_stack;
+        }
 
         ret = i915_mutex_lock_interruptible(dev);
         if (ret)
@@ -2122,9 +2125,11 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
         drm_gem_object_unreference(&obj->base);
         mutex_unlock(&dev->struct_mutex);
 
-        ret = __wait_seqno(ring, seqno, true, &timeout);
-        WARN_ON(!timespec_valid(&timeout));
-        args->timeout_ns = timespec_to_ns(&timeout);
+        ret = __wait_seqno(ring, seqno, true, timeout);
+        if (timeout) {
+                WARN_ON(!timespec_valid(timeout));
+                args->timeout_ns = timespec_to_ns(timeout);
+        }
         return ret;
 
 out: