drm/i915: Markup paired operations on wakerefs

The majority of runtime-pm operations are bounded and scoped within a
function; these are easy to verify that the wakeref are handled
correctly. We can employ the compiler to help us, and reduce the number
of wakerefs tracked when debugging, by passing around cookies provided
by the various rpm_get functions to their rpm_put counterpart. This
makes the pairing explicit, and given the required wakeref cookie the
compiler can verify that we pass an initialised value to the rpm_put
(quite handy for double checking error paths).

For regular builds, the compiler should be able to eliminate the unused
local variables and the program growth should be minimal. Fwiw, it came
out as a net improvement as gcc was able to refactor rpm_get and
rpm_get_if_in_use together,

v2: Just s/rpm_put/rpm_put_unchecked/ everywhere, leaving the manual
mark up for smaller more targeted patches.
v3: Mention the cookie in Returns

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190114142129.24398-2-chris@chris-wilson.co.uk

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 5990f8500bca..2e60463f2468 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -928,7 +928,7 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
 	if (INTEL_GEN(dev_priv) > 2 && !(I915_READ_MODE(engine) & MODE_IDLE))
 		idle = false;
 
-	intel_runtime_pm_put(dev_priv);
+	intel_runtime_pm_put_unchecked(dev_priv);
 
 	return idle;
 }
@@ -1485,7 +1485,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 
 	if (intel_runtime_pm_get_if_in_use(engine->i915)) {
 		intel_engine_print_registers(engine, m);
-		intel_runtime_pm_put(engine->i915);
+		intel_runtime_pm_put_unchecked(engine->i915);
 	} else {
 		drm_printf(m, "\tDevice is asleep; skipping register dump\n");
 	}