[Intel-gfx] [PATCH] drm/i915: increase the default timeout in wait_seqno to 60s

[Daniel Vetter]

We'll loop forever, but if we wake up before the hangcheck time has a
chance to complain that we're stuck waiting for the interrupt we'll
loose that valuable debug tool. And silently blocking for 1 second is
just not the right approach.

Noticed since Paulo reported a suspicious 2 fps when running glxgears
with pc8+ enabled. Since mesa stalls for the second-last frame before
rendering a new one this is perfectly explained by hitting the 1
second timeout.

This regression has been introduced in Ben's wait with timeout ioctl
work in:

commit 5c81fe85dad3c8c2bcec03e3fc2bfd4ea198763c
Author: Ben Widawsky <ben at bwidawsk.net>
Date:   Thu May 24 15:03:08 2012 -0700

    drm/i915: timeout parameter for seqno wait

Also fix whitespace in that line while at it and add an explicit
comment.

Cc: Ben Widawsky <ben at bwidawsk.net>
Cc: Paulo Zanoni <przanoni at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8508b3d..84170fe 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -986,7 +986,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 			bool interruptible, struct timespec *timeout)
 {
 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
-	struct timespec before, now, wait_time={1,0};
+	struct timespec before, now, wait_time;
 	unsigned long timeout_jiffies;
 	long end;
 	bool wait_forever = true;
@@ -1000,6 +1000,14 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 	if (timeout != NULL) {
 		wait_time = *timeout;
 		wait_forever = false;
+	} else {
+		/*
+		 * The timeout here must be longer than the hangcheck timeout,
+		 * otherwise we'll no longer detect missed interrupts but end up
+		 * with dead-slow rendering.
+		 */
+		wait_time.tv_sec = 60;
+		wait_time.tv_nsec = 0;
 	}
 
 	timeout_jiffies = timespec_to_jiffies_timeout(&wait_time);
-- 
1.8.3.2