On 03/07/2019 12:47, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2019-07-03 12:23:52)
On 03/07/2019 10:17, Chris Wilson wrote:
During post-reset resume, we call intel_mocs_init_engine to reinitialise
the MOCS registers. Suprisingly, especially when enhanced by lockdep,
the acquisition of the forcewake lock around each register write takes a
substantial portion of the reset time. We don't need to use the
individual forcewake here as we can assume that the caller is holding a
blanket forcewake for the reset&resume and the resume is serialised.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_mocs.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
index ae6cbf0d517c..290a5e9b90b9 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -346,6 +346,9 @@ void intel_mocs_init_engine(struct intel_engine_cs *engine)
unsigned int index;
u32 unused_value;
+ /* Called under a blanket forcewake */
+ assert_forcewakes_active(uncore, FORCEWAKE_ALL);
+
Assert is strictly speaking a bit weak since forcewake status can
theoretically change until the actual access below. But in our current
code we indeed hold it for the whole reset.
You want to distinguish between an explicit hold by the caller and the
auto.
Yes, we just don't have a way of distinguishing if the caller is holding
or they were held and about to be released.
I don't have any actual ideas on how to fundamentally improve the
assert. Thought to have it after the writes is the only thing which came
to mind. Thoughts?
I definitely prefer having it upfront to document the function
preconditions, and so would prefer if the assert actually did assert an
explicit forcewake as it is meant to do :)
Probably better yes. I was just thinking out loud.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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