[PATCH] drm/i915/guc: Enable send function only after successful init

[Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>]

It is safer to setup valid send function after successful GuC
hardware initialization. In addition we prepare placeholder
where we can setup any alternate GuC communication mechanism.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_uc.c | 27 ++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_uc.h |  1 +
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_uc.c b/drivers/gpu/drm/i915/intel_uc.c
index 900e376..5957a95 100644
--- a/drivers/gpu/drm/i915/intel_uc.c
+++ b/drivers/gpu/drm/i915/intel_uc.c
@@ -99,7 +99,7 @@ void intel_uc_init_early(struct drm_i915_private *dev_priv)
 	struct intel_guc *guc = &dev_priv->guc;
 
 	mutex_init(&guc->send_mutex);
-	guc->send = intel_guc_send_mmio;
+	guc->send = intel_guc_send_nop;
 }
 
 static void fetch_uc_fw(struct drm_i915_private *dev_priv,
@@ -252,13 +252,27 @@ void intel_uc_fini_fw(struct drm_i915_private *dev_priv)
 	__intel_uc_fw_fini(&dev_priv->huc.fw);
 }
 
+static int guc_enable_communication(struct intel_guc *guc)
+{
+	/* XXX: placeholder for alternate setup */
+	guc->send = intel_guc_send_mmio;
+	return 0;
+}
+
+static void guc_disable_communication(struct intel_guc *guc)
+{
+	guc->send = intel_guc_send_nop;
+}
+
 int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 {
+	struct intel_guc *guc = &dev_priv->guc;
 	int ret, attempts;
 
 	if (!i915.enable_guc_loading)
 		return 0;
 
+	guc_disable_communication(guc);
 	gen9_reset_guc_interrupts(dev_priv);
 
 	/* We need to notify the guc whenever we change the GGTT */
@@ -308,6 +322,10 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 	if (ret)
 		goto err_submission;
 
+	ret = guc_enable_communication(guc);
+	if (ret)
+		goto err_submission;
+
 	intel_guc_auth_huc(dev_priv);
 	if (i915.enable_guc_submission) {
 		if (i915.guc_log_level >= 0)
@@ -330,6 +348,7 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 	 * marks the GPU as wedged until reset).
 	 */
 err_interrupts:
+	guc_disable_communication(guc);
 	gen9_disable_guc_interrupts(dev_priv);
 err_submission:
 	if (i915.enable_guc_submission)
@@ -364,6 +383,12 @@ void intel_uc_fini_hw(struct drm_i915_private *dev_priv)
 	i915_ggtt_disable_guc(dev_priv);
 }
 
+int intel_guc_send_nop(struct intel_guc *guc, const u32 *action, u32 len)
+{
+	WARN(1, "Unexpected send: action=%#x\n", *action);
+	return -ENOSYS;
+}
+
 /*
  * This function implements the MMIO based host to GuC interface.
  */
diff --git a/drivers/gpu/drm/i915/intel_uc.h b/drivers/gpu/drm/i915/intel_uc.h
index 2f0229d..1e0eecd 100644
--- a/drivers/gpu/drm/i915/intel_uc.h
+++ b/drivers/gpu/drm/i915/intel_uc.h
@@ -227,6 +227,7 @@ void intel_uc_fini_fw(struct drm_i915_private *dev_priv);
 int intel_uc_init_hw(struct drm_i915_private *dev_priv);
 void intel_uc_fini_hw(struct drm_i915_private *dev_priv);
 int intel_guc_sample_forcewake(struct intel_guc *guc);
+int intel_guc_send_nop(struct intel_guc *guc, const u32 *action, u32 len);
 int intel_guc_send_mmio(struct intel_guc *guc, const u32 *action, u32 len);
 static inline int intel_guc_send(struct intel_guc *guc, const u32 *action, u32 len)
 {
-- 
2.7.4

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