From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 1 May 2018 08:52:03 +0100
Subject: drm/i915/guc: Assert we have the doorbell before setting it up
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Git-commit: 0d4b78b3d2c0cb570abe086bce8c17ea3c474095
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

As our early doorbell is split between early allocation and a late setup
after we have a channel to the GuC, it may happen due to a lapse of
programmer judgement that we try to setup an invalid doorbell. Make use
of our has_doorbell() function to check the doorbell does exist for the
client before we try and tell the guc about it. In doing so, we prevent
the compiler from warning about the otherwise unused function in some
configurations.

Reported-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180501075203.12458-1-chris@chris-wilson.co.uk

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_guc_submission.c |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -124,9 +124,17 @@ static int reserve_doorbell(struct intel
 	return 0;
 }
 
+static bool has_doorbell(struct intel_guc_client *client)
+{
+	if (client->doorbell_id == GUC_DOORBELL_INVALID)
+		return false;
+
+	return test_bit(client->doorbell_id, client->guc->doorbell_bitmap);
+}
+
 static void unreserve_doorbell(struct intel_guc_client *client)
 {
-	GEM_BUG_ON(client->doorbell_id == GUC_DOORBELL_INVALID);
+	GEM_BUG_ON(!has_doorbell(client));
 
 	__clear_bit(client->doorbell_id, client->guc->doorbell_bitmap);
 	client->doorbell_id = GUC_DOORBELL_INVALID;
@@ -184,14 +192,6 @@ static struct guc_doorbell_info *__get_d
 	return client->vaddr + client->doorbell_offset;
 }
 
-static bool has_doorbell(struct intel_guc_client *client)
-{
-	if (client->doorbell_id == GUC_DOORBELL_INVALID)
-		return false;
-
-	return test_bit(client->doorbell_id, client->guc->doorbell_bitmap);
-}
-
 static void __create_doorbell(struct intel_guc_client *client)
 {
 	struct guc_doorbell_info *doorbell;
@@ -207,7 +207,6 @@ static void __destroy_doorbell(struct in
 	struct guc_doorbell_info *doorbell;
 	u16 db_id = client->doorbell_id;
 
-
 	doorbell = __get_doorbell(client);
 	doorbell->db_status = GUC_DOORBELL_DISABLED;
 	doorbell->cookie = 0;
@@ -224,6 +223,9 @@ static int create_doorbell(struct intel_
 {
 	int ret;
 
+	if (WARN_ON(!has_doorbell(client)))
+		return -ENODEV; /* internal setup error, should never happen */
+
 	__update_doorbell_desc(client, client->doorbell_id);
 	__create_doorbell(client);