Re: [PATCH 03/26] drm/i915/guc: Take engine PM when a context is pinned with GuC submission

[John Harrison <john.c.harrison@xxxxxxxxx>]

On 10/4/2021 15:06, Matthew Brost wrote:
> Taking a PM reference to prevent intel_gt_wait_for_idle from short
> circuiting while a scheduling of user context could be enabled.
I'm not sure what 'while a scheduling of user context could be enabled' 
means.

John.

> Returning GT idle when it is not can cause all sorts of issues
> throughout the stack.
>
> v2:
>   (Daniel Vetter)
>    - Add might_lock annotations to pin / unpin function
> v3:
>   (CI)
>    - Drop intel_engine_pm_might_put from unpin path as an async put is
>      used
> v4:
>   (John Harrison)
>    - Make intel_engine_pm_might_get/put work with GuC virtual engines
>    - Update commit message
>
> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/gt/intel_context.c       |  2 ++
>   drivers/gpu/drm/i915/gt/intel_engine_pm.h     | 32 +++++++++++++++++
>   drivers/gpu/drm/i915/gt/intel_gt_pm.h         | 10 ++++++
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 36 +++++++++++++++++--
>   drivers/gpu/drm/i915/intel_wakeref.h          | 12 +++++++
>   5 files changed, 89 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 1076066f41e0..f601323b939f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -240,6 +240,8 @@ int __intel_context_do_pin_ww(struct intel_context *ce,
>   	if (err)
>   		goto err_post_unpin;
>   
> +	intel_engine_pm_might_get(ce->engine);
> +
>   	if (unlikely(intel_context_is_closed(ce))) {
>   		err = -ENOENT;
>   		goto err_unlock;
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> index 6fdeae668e6e..d68675925b79 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> @@ -6,9 +6,11 @@
>   #ifndef INTEL_ENGINE_PM_H
>   #define INTEL_ENGINE_PM_H
>   
> +#include "i915_drv.h"
>   #include "i915_request.h"
>   #include "intel_engine_types.h"
>   #include "intel_wakeref.h"
> +#include "intel_gt_pm.h"
>   
>   static inline bool
>   intel_engine_pm_is_awake(const struct intel_engine_cs *engine)
> @@ -31,6 +33,21 @@ static inline bool intel_engine_pm_get_if_awake(struct intel_engine_cs *engine)
>   	return intel_wakeref_get_if_active(&engine->wakeref);
>   }
>   
> +static inline void intel_engine_pm_might_get(struct intel_engine_cs *engine)
> +{
> +	if (!intel_engine_is_virtual(engine)) {
> +		intel_wakeref_might_get(&engine->wakeref);
> +	} else {
> +		struct intel_gt *gt = engine->gt;
> +		struct intel_engine_cs *tengine;
> +		intel_engine_mask_t tmp, mask = engine->mask;
> +
> +		for_each_engine_masked(tengine, gt, mask, tmp)
> +			intel_wakeref_might_get(&tengine->wakeref);
> +	}
> +	intel_gt_pm_might_get(engine->gt);
> +}
> +
>   static inline void intel_engine_pm_put(struct intel_engine_cs *engine)
>   {
>   	intel_wakeref_put(&engine->wakeref);
> @@ -52,6 +69,21 @@ static inline void intel_engine_pm_flush(struct intel_engine_cs *engine)
>   	intel_wakeref_unlock_wait(&engine->wakeref);
>   }
>   
> +static inline void intel_engine_pm_might_put(struct intel_engine_cs *engine)
> +{
> +	if (!intel_engine_is_virtual(engine)) {
> +		intel_wakeref_might_put(&engine->wakeref);
> +	} else {
> +		struct intel_gt *gt = engine->gt;
> +		struct intel_engine_cs *tengine;
> +		intel_engine_mask_t tmp, mask = engine->mask;
> +
> +		for_each_engine_masked(tengine, gt, mask, tmp)
> +			intel_wakeref_might_put(&tengine->wakeref);
> +	}
> +	intel_gt_pm_might_put(engine->gt);
> +}
> +
>   static inline struct i915_request *
>   intel_engine_create_kernel_request(struct intel_engine_cs *engine)
>   {
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> index 05de6c1af25b..bc898df7a48c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> @@ -31,6 +31,11 @@ static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
>   	return intel_wakeref_get_if_active(&gt->wakeref);
>   }
>   
> +static inline void intel_gt_pm_might_get(struct intel_gt *gt)
> +{
> +	intel_wakeref_might_get(&gt->wakeref);
> +}
> +
>   static inline void intel_gt_pm_put(struct intel_gt *gt)
>   {
>   	intel_wakeref_put(&gt->wakeref);
> @@ -41,6 +46,11 @@ static inline void intel_gt_pm_put_async(struct intel_gt *gt)
>   	intel_wakeref_put_async(&gt->wakeref);
>   }
>   
> +static inline void intel_gt_pm_might_put(struct intel_gt *gt)
> +{
> +	intel_wakeref_might_put(&gt->wakeref);
> +}
> +
>   #define with_intel_gt_pm(gt, tmp) \
>   	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
>   	     intel_gt_pm_put(gt), tmp = 0)
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 17da2fea1bff..8b82da50c2bc 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1571,7 +1571,12 @@ static int guc_context_pre_pin(struct intel_context *ce,
>   
>   static int guc_context_pin(struct intel_context *ce, void *vaddr)
>   {
> -	return __guc_context_pin(ce, ce->engine, vaddr);
> +	int ret = __guc_context_pin(ce, ce->engine, vaddr);
> +
> +	if (likely(!ret && !intel_context_is_barrier(ce)))
> +		intel_engine_pm_get(ce->engine);
> +
> +	return ret;
>   }
>   
>   static void guc_context_unpin(struct intel_context *ce)
> @@ -1580,6 +1585,9 @@ static void guc_context_unpin(struct intel_context *ce)
>   
>   	unpin_guc_id(guc, ce);
>   	lrc_unpin(ce);
> +
> +	if (likely(!intel_context_is_barrier(ce)))
> +		intel_engine_pm_put_async(ce->engine);
>   }
>   
>   static void guc_context_post_unpin(struct intel_context *ce)
> @@ -2341,8 +2349,30 @@ static int guc_virtual_context_pre_pin(struct intel_context *ce,
>   static int guc_virtual_context_pin(struct intel_context *ce, void *vaddr)
>   {
>   	struct intel_engine_cs *engine = guc_virtual_get_sibling(ce->engine, 0);
> +	int ret = __guc_context_pin(ce, engine, vaddr);
> +	intel_engine_mask_t tmp, mask = ce->engine->mask;
> +
> +	if (likely(!ret))
> +		for_each_engine_masked(engine, ce->engine->gt, mask, tmp)
> +			intel_engine_pm_get(engine);
>   
> -	return __guc_context_pin(ce, engine, vaddr);
> +	return ret;
> +}
> +
> +static void guc_virtual_context_unpin(struct intel_context *ce)
> +{
> +	intel_engine_mask_t tmp, mask = ce->engine->mask;
> +	struct intel_engine_cs *engine;
> +	struct intel_guc *guc = ce_to_guc(ce);
> +
> +	GEM_BUG_ON(context_enabled(ce));
> +	GEM_BUG_ON(intel_context_is_barrier(ce));
> +
> +	unpin_guc_id(guc, ce);
> +	lrc_unpin(ce);
> +
> +	for_each_engine_masked(engine, ce->engine->gt, mask, tmp)
> +		intel_engine_pm_put_async(engine);
>   }
>   
>   static void guc_virtual_context_enter(struct intel_context *ce)
> @@ -2379,7 +2409,7 @@ static const struct intel_context_ops virtual_guc_context_ops = {
>   
>   	.pre_pin = guc_virtual_context_pre_pin,
>   	.pin = guc_virtual_context_pin,
> -	.unpin = guc_context_unpin,
> +	.unpin = guc_virtual_context_unpin,
>   	.post_unpin = guc_context_post_unpin,
>   
>   	.ban = guc_context_ban,
> diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
> index 545c8f277c46..4f4c2e15e736 100644
> --- a/drivers/gpu/drm/i915/intel_wakeref.h
> +++ b/drivers/gpu/drm/i915/intel_wakeref.h
> @@ -123,6 +123,12 @@ enum {
>   	__INTEL_WAKEREF_PUT_LAST_BIT__
>   };
>   
> +static inline void
> +intel_wakeref_might_get(struct intel_wakeref *wf)
> +{
> +	might_lock(&wf->mutex);
> +}
> +
>   /**
>    * intel_wakeref_put_flags: Release the wakeref
>    * @wf: the wakeref
> @@ -170,6 +176,12 @@ intel_wakeref_put_delay(struct intel_wakeref *wf, unsigned long delay)
>   			    FIELD_PREP(INTEL_WAKEREF_PUT_DELAY, delay));
>   }
>   
> +static inline void
> +intel_wakeref_might_put(struct intel_wakeref *wf)
> +{
> +	might_lock(&wf->mutex);
> +}
> +
>   /**
>    * intel_wakeref_lock: Lock the wakeref (mutex)
>    * @wf: the wakeref