[Intel-gfx] [PATCH 07/11] drm/i915/tdr: Add support for per engine reset recovery

[Arun Siluvery]

This change implements support for per-engine reset as an initial, less
intrusive hang recovery option to be attempted before falling back to the
legacy full GPU reset recovery mode if necessary. This is only supported
from Gen8 onwards.

Hangchecker determines which engines are hung and invokes error handler to
recover from it. Error handler schedules recovery for each of those engines
that are hung. The recovery procedure is as follows,
 - force engine to idle: this is done by issuing a reset request
 - identifies the request that caused the hang and it is dropped
 - reset and re-init engine
 - restart submissions to the engine

If engine reset fails then we fall back to heavy weight full gpu reset
which resets all engines and reinitiazes complete state of HW and SW.

Possible reasons for failure,
 - engine not ready for reset
 - if the HW and SW doesn't agree on the context that caused the hang
 - reset itself failed for some reason

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Signed-off-by: Tomas Elf <tomas.elf at intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c     | 55 +++++++++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/i915_drv.h     |  3 ++
 drivers/gpu/drm/i915/i915_gem.c     |  2 +-
 drivers/gpu/drm/i915/intel_lrc.h    |  4 +++
 drivers/gpu/drm/i915/intel_uncore.c | 33 ++++++++++++++++++++++
 5 files changed, 90 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 5c20e5d..8151aa9 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1824,17 +1824,60 @@ error:
  * Returns zero on successful reset or otherwise an error code.
  *
  * Procedure is fairly simple:
- *  - force engine to idle
- *  - save current state which includes head and current request
- *  - reset engine
- *  - restore saved state and resubmit context
+ *    - force engine to idle: this is done by issuing a reset request
+ *    - identifies the request that caused the hang and it is retired
+ *    - reset engine
+ *    - restart submissions to the engine
  */
 int i915_reset_engine(struct intel_engine_cs *engine)
 {
+	struct drm_i915_private *dev_priv = engine->i915;
 	int ret;
 
-	/* FIXME: replace me with engine reset sequence */
-	ret = -ENODEV;
+	/* Ensure irq handler finishes or is cancelled. */
+	tasklet_kill(&engine->irq_tasklet);
+
+	i915_gem_reset_engine_status(engine);
+
+	/*Take wake lock to prevent power saving mode */
+	intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
+
+	ret = intel_request_for_reset(engine);
+	if (ret) {
+		DRM_ERROR("Failed to disable %s\n", engine->name);
+		goto out;
+	}
+
+	ret = intel_execlists_reset_prepare(engine);
+	if (ret)
+		goto enable_engine;
+
+	ret = intel_gpu_reset(dev_priv, intel_engine_flag(engine));
+	if (ret) {
+		DRM_ERROR("Failed to reset %s, ret=%d\n", engine->name, ret);
+		goto enable_engine;
+	}
+
+	ret = engine->init_hw(engine);
+	if (ret)
+		goto out;
+
+	/* Restart submissions to the engine after reset */
+	intel_execlists_restart_submission(engine);
+
+enable_engine:
+	/*
+	 * we only need to enable engine if we cannot prepare engine for
+	 * reset or reset fails. If the reset is successful, engine gets
+	 * enabled automatically so we can skip this step.
+	 */
+	if (ret)
+		intel_clear_reset_request(engine);
+
+out:
+	/* Wake up anything waiting on this engine's queue */
+	intel_engine_wakeup(engine);
+	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 
 	return ret;
 }
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 61e57a8b..ac7a42c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2837,6 +2837,8 @@ extern int intel_gpu_reset(struct drm_i915_private *dev_priv, u32 engine_mask);
 extern bool intel_has_gpu_reset(struct drm_i915_private *dev_priv);
 extern int i915_reset(struct drm_i915_private *dev_priv);
 extern bool intel_has_engine_reset(struct drm_i915_private *dev_priv);
+extern int intel_request_for_reset(struct intel_engine_cs *engine);
+extern int intel_clear_reset_request(struct intel_engine_cs *engine);
 extern int i915_reset_engine(struct intel_engine_cs *engine);
 extern int intel_guc_reset(struct drm_i915_private *dev_priv);
 extern void intel_engine_init_hangcheck(struct intel_engine_cs *engine);
@@ -3231,6 +3233,7 @@ static inline bool i915_engine_reset_in_progress(struct i915_gpu_error *error,
 }
 
 void i915_gem_reset(struct drm_device *dev);
+void i915_gem_reset_engine_status(struct intel_engine_cs *ring);
 bool i915_gem_clflush_object(struct drm_i915_gem_object *obj, bool force);
 int __must_check i915_gem_init(struct drm_device *dev);
 int __must_check i915_gem_init_hw(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 443570f..e34effb 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2468,7 +2468,7 @@ i915_gem_find_active_request(struct intel_engine_cs *engine)
 	return NULL;
 }
 
-static void i915_gem_reset_engine_status(struct intel_engine_cs *engine)
+void i915_gem_reset_engine_status(struct intel_engine_cs *engine)
 {
 	struct drm_i915_gem_request *request;
 	bool ring_hung;
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 1171ea1..4035f63 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -132,4 +132,8 @@ int intel_execlists_submission(struct i915_execbuffer_params *params,
 
 void intel_execlists_cancel_requests(struct intel_engine_cs *engine);
 
+/* Engine reset */
+int intel_execlists_reset_prepare(struct intel_engine_cs *engine);
+void intel_execlists_restart_submission(struct intel_engine_cs *engine);
+
 #endif /* _INTEL_LRC_H_ */
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 418fd0d..d807871 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1799,6 +1799,39 @@ int intel_guc_reset(struct drm_i915_private *dev_priv)
 	return ret;
 }
 
+/*
+ * On gen8+ a reset request has to be issued via the reset control register
+ * before a GPU engine can be reset in order to stop the command streamer
+ * and idle the engine. This replaces the legacy way of stopping an engine
+ * by writing to the stop ring bit in the MI_MODE register.
+ */
+int intel_request_for_reset(struct intel_engine_cs *engine)
+{
+	if (!intel_has_engine_reset(engine->i915)) {
+		DRM_ERROR("Engine Reset not supported on Gen%d\n",
+			  INTEL_INFO(engine->i915)->gen);
+		return -EINVAL;
+	}
+
+	return gen8_request_engine_reset(engine);
+}
+
+/*
+ * It is possible to back off from a previously issued reset request by simply
+ * clearing the reset request bit in the reset control register.
+ */
+int intel_clear_reset_request(struct intel_engine_cs *engine)
+{
+	if (!intel_has_engine_reset(engine->i915)) {
+		DRM_ERROR("Request to clear reset not supported on Gen%d\n",
+			  INTEL_INFO(engine->i915)->gen);
+		return -EINVAL;
+	}
+
+	gen8_unrequest_engine_reset(engine);
+	return 0;
+}
+
 bool intel_uncore_unclaimed_mmio(struct drm_i915_private *dev_priv)
 {
 	return check_for_unclaimed_mmio(dev_priv);
-- 
1.9.1