On 2012-08-26 23:59, Jani Nikula wrote:
On Fri, 24 Aug 2012, Ben Widawsky <b...@bwidawsk.net> wrote:
A designer familiar with the hardware has stated that the forcewake
timeout can theoretically be as high as a little over 1ms. Therefore
we
modify our code to use 2ms (appropriate fudge and because we don't
want
to round down).
Hopefully this can't prevent spurious timeouts.
Signed-off-by: Ben Widawsky <b...@bwidawsk.net>
---
drivers/gpu/drm/i915/intel_pm.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c
b/drivers/gpu/drm/i915/intel_pm.c
index f42c142..2a8468d 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -31,7 +31,7 @@
#include "../../../platform/x86/intel_ips.h"
#include <linux/module.h>
-#define FORCEWAKE_ACK_TIMEOUT_US 500
+#define FORCEWAKE_ACK_TIMEOUT_MS 2
/* FBC, or Frame Buffer Compression, is a technique employed to
compress the
* framebuffer contents in-memory, aiming at reducing the required
bandwidth
@@ -3970,15 +3970,15 @@ static void __gen6_gt_force_wake_get(struct
drm_i915_private *dev_priv)
else
forcewake_ack = FORCEWAKE_ACK;
- if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) ==
0,
- FORCEWAKE_ACK_TIMEOUT_US))
+ if (wait_for_atomic((I915_READ_NOTRACE(forcewake_ack) & 1) == 0,
+ FORCEWAKE_ACK_TIMEOUT_MS))
Superficially this looks okay, but the implementation of
wait_for_atomic() not so. As a surprise, this change drops
cpu_relax()
from the busy loop, even thought the timeout is potentially much
longer.
The quick fix here would be to just use 2000 us with
wait_for_atomic_us(), but we should do something about
wait_for_atomic()
too. Luckily it's only ever used at one place.
BR,
Jani.
Hmm, dare I say, I think this is a bug in _wait_for. Without spending
too much brain power on this, I believe the compiler can screw us over
here. No matter the bug, cpu_relax is still probably desirable, unless
there is some newer coolness here? I shall insert a patch before this to
do the cpu_relax in _wait_for.
Nice catch.
Ben
DRM_ERROR("Force wake wait timed out\n");
I915_WRITE_NOTRACE(FORCEWAKE, 1);
POSTING_READ(FORCEWAKE);
- if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1),
- FORCEWAKE_ACK_TIMEOUT_US))
+ if (wait_for_atomic((I915_READ_NOTRACE(forcewake_ack) & 1),
+ FORCEWAKE_ACK_TIMEOUT_MS))
DRM_ERROR("Force wake wait timed out\n");
__gen6_gt_wait_for_thread_c0(dev_priv);
@@ -3993,15 +3993,15 @@ static void
__gen6_gt_force_wake_mt_get(struct drm_i915_private *dev_priv)
else
forcewake_ack = FORCEWAKE_MT_ACK;
- if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) ==
0,
- FORCEWAKE_ACK_TIMEOUT_US))
+ if (wait_for_atomic((I915_READ_NOTRACE(forcewake_ack) & 1) == 0,
+ FORCEWAKE_ACK_TIMEOUT_MS))
DRM_ERROR("Force wake wait timed out\n");
I915_WRITE_NOTRACE(FORCEWAKE_MT, _MASKED_BIT_ENABLE(1));
POSTING_READ(FORCEWAKE_MT);
- if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1),
- FORCEWAKE_ACK_TIMEOUT_US))
+ if (wait_for_atomic((I915_READ_NOTRACE(forcewake_ack) & 1),
+ FORCEWAKE_ACK_TIMEOUT_MS))
DRM_ERROR("Force wake wait timed out\n");
__gen6_gt_wait_for_thread_c0(dev_priv);
@@ -4088,8 +4088,8 @@ static void vlv_force_wake_get(struct
drm_i915_private *dev_priv)
I915_WRITE_NOTRACE(FORCEWAKE_VLV, 0xffffffff);
POSTING_READ(FORCEWAKE_VLV);
- if (wait_for_atomic_us((I915_READ_NOTRACE(FORCEWAKE_ACK_VLV) & 1),
- FORCEWAKE_ACK_TIMEOUT_US))
+ if (wait_for_atomic((I915_READ_NOTRACE(FORCEWAKE_ACK_VLV) & 1),
+ FORCEWAKE_ACK_TIMEOUT_MS))
DRM_ERROR("Force wake wait timed out\n");
__gen6_gt_wait_for_thread_c0(dev_priv);
--
1.7.12
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ben Widawsky, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx
