From ff320d6e72ff3600184a1c01ea75b689b4b8a16d Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 23 Oct 2017 22:32:35 +0100
Subject: [PATCH] drm/i915: Synchronize irq before parking each engine
Git-commit: ff320d6e72ff3600184a1c01ea75b689b4b8a16d
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900
When we park the engine (upon idling), we kill the irq tasklet. However,
to be sure that it is not restarted by a spurious interrupt after doing so,
flush the interrupt handler before parking. As we only park the engines
when we believe the system is idle, there should not be any interrupts to
distrub us; so flushing the final in-flight interrupt should be sufficient.
(However, we are still dependent on the HW behaving in an orderly and
timely fashion, which we shall endeavour to improve upon later.)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171023213237.26536-2-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_gem.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3323,6 +3323,19 @@ i915_gem_idle_work_handler(struct work_s
goto out_unlock;
/*
+ * Be paranoid and flush a concurrent interrupt to make sure
+ * we don't reactivate any irq tasklets after parking.
+ *
+ * FIXME: Note that even though we have waited for execlists to be idle,
+ * there may still be an in-flight interrupt even though the CSB
+ * is now empty. synchronize_irq() makes sure that a residual interrupt
+ * is completed before we continue, but it doesn't prevent the HW from
+ * raising a spurious interrupt later. To complete the shield we should
+ * coordinate disabling the CS irq with flushing the interrupts.
+ */
+ synchronize_irq(dev_priv->drm.irq);
+
+ /*
* We are committed now to parking the engines, make sure there
* will be no more interrupts arriving later.
*/