From cdb6ded42f735396197906de04316d9b0e10c987 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 21 Jul 2017 13:32:22 +0100
Subject: [PATCH] drm/i915: Flush the execlist ports if idle
Git-commit: cdb6ded42f735396197906de04316d9b0e10c987
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

When doing a GPU reset, the CSB register will be trashed and we will
lose any context-switch notifications that happened since the tasklet
was disabled. If we find that all requests on this engine were
completed, we want to make sure that the ELSP tracker is similarly empty
so that we do not feed back in the completed requests upon recovering
from the reset.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@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/20170721123238.16428-4-chris@chris-wilson.co.uk
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_lrc.c |   36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1327,6 +1327,31 @@ static void reset_common_ring(struct int
 {
 	struct execlist_port *port = engine->execlist_port;
 	struct intel_context *ce;
+	unsigned int n;
+
+	/*
+	 * Catch up with any missed context-switch interrupts.
+	 *
+	 * Ideally we would just read the remaining CSB entries now that we
+	 * know the gpu is idle. However, the CSB registers are sometimes^W
+	 * often trashed across a GPU reset! Instead we have to rely on
+	 * guessing the missed context-switch events by looking at what
+	 * requests were completed.
+	 */
+	if (!request) {
+		for (n = 0; n < ARRAY_SIZE(engine->execlist_port); n++)
+			i915_gem_request_put(port_request(&port[n]));
+		memset(engine->execlist_port, 0, sizeof(engine->execlist_port));
+		return;
+	}
+
+	if (request->ctx != port_request(port)->ctx) {
+		i915_gem_request_put(port_request(port));
+		port[0] = port[1];
+		memset(&port[1], 0, sizeof(port[1]));
+	}
+
+	GEM_BUG_ON(request->ctx != port_request(port)->ctx);
 
 	/* If the request was innocent, we leave the request in the ELSP
 	 * and will try to replay it on restarting. The context image may
@@ -1338,7 +1363,7 @@ static void reset_common_ring(struct int
 	 * and have to at least restore the RING register in the context
 	 * image back to the expected values to skip over the guilty request.
 	 */
-	if (!request || request->fence.error != -EIO)
+	if (request->fence.error != -EIO)
 		return;
 
 	/* We want a simple context + ring to execute the breadcrumb update.
@@ -1360,15 +1385,6 @@ static void reset_common_ring(struct int
 	request->ring->head = request->postfix;
 	intel_ring_update_space(request->ring);
 
-	/* Catch up with any missed context-switch interrupts */
-	if (request->ctx != port_request(port)->ctx) {
-		i915_gem_request_put(port_request(port));
-		port[0] = port[1];
-		memset(&port[1], 0, sizeof(port[1]));
-	}
-
-	GEM_BUG_ON(request->ctx != port_request(port)->ctx);
-
 	/* Reset WaIdleLiteRestore:bdw,skl as well */
 	request->tail =
 		intel_ring_wrap(request->ring,