From 48921260b7d030ec6a2e11a435eae28ddb88ea56 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 11 Apr 2017 18:58:50 +0100
Subject: [PATCH] drm/i915/execlists: Document runtime pm for intel_lrc_irq_handler()
Git-commit: 48921260b7d030ec6a2e11a435eae28ddb88ea56
Patch-mainline: v4.13-rc1
References: FATE#322643 bsc#1055900

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@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170411175850.2470-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_lrc.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -514,6 +514,15 @@ static void intel_lrc_irq_handler(unsign
 	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