On 12/04/2017 09:31, Chris Wilson wrote:
On Wed, Apr 12, 2017 at 08:12:17AM +0100, Tvrtko Ursulin wrote:
On 11/04/2017 18:58, Chris Wilson wrote:
We indirectly hold the runtime-pm for the intel_lrc_irq_handler() by
virtue of dev_priv->gt.awake keeping a wakeref whilst the requests are
busy. As this is not obvious from the code, add a comment.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 0dc1cc4ad6e7..e16cc28dc783 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -515,6 +515,15 @@ static void intel_lrc_irq_handler(unsigned long data)
struct execlist_port *port = engine->execlist_port;
struct drm_i915_private *dev_priv = engine->i915;
+ /* We can skip acquiring intel_runtime_pm_get() here as it was taken
+ * on our behalf by the request (see i915_gem_mark_busy ()) and it will
+ * not be relinquished until the device is idle (see
+ * i915_gem_idle_work_handler()). As a precaution, we make sure
+ * that all ELSP are drained i.e. we have processed the CSB,
+ * before allowing ourselves to idle and calling intel_runtime_pm_put().
+ */
+ GEM_BUG_ON(!dev_priv->gt.awake);
+
intel_uncore_forcewake_get(dev_priv, engine->fw_domains);
/* Prefer doing test_and_clear_bit() as a two stage operation to avoid
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
It feels a big to c&p, but not sure if it worth putting a comment
"see comment in intel_lrc_irq_handler on why we don't have to " to
i915_guc_irq_handler or maybe dequeue?
For guc, the requirement for rpm is much less strict - the interface
with the guc is through ordinary memory not device memory, so we don't
need rpm_get (aiui). There is the mmio readback for !llc to ensure that
all GTT writes are flushed to system memory prior to dispatching the
workqueue -- that technically doesn't require rpm either.
I'm a bit more hesistant about adding such a comment to the guc atm, as
I think I will be more misleading then helpful.
I am not sure but was thinking that presumably device needs to be awake
as we are adding stuff into the GuC's workqueue.
Regards,
Tvrtko
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