Re: [Intel-gfx] [PATCH 06/27] drm/i915/guc: Take engine PM when a context is pinned with GuC submission

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

On 8/20/2021 15:44, 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.
As with earlier PM patch, needs more explanation of what the problem is 
and why it is only now a problem.


> v2:
>   (Daniel Vetter)
>    - Add might_lock annotations to pin / unpin function
>
> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/gt/intel_context.c       |  3 ++
>   drivers/gpu/drm/i915/gt/intel_engine_pm.h     | 15 ++++++++
>   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, 73 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index c8595da64ad8..508cfe5770c0 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;
> @@ -313,6 +315,7 @@ void __intel_context_do_unpin(struct intel_context *ce, int sub)
>   		return;
>   
>   	CE_TRACE(ce, "unpin\n");
> +	intel_engine_pm_might_put(ce->engine);
>   	ce->ops->unpin(ce);
>   	ce->ops->post_unpin(ce);
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> index 17a5028ea177..3fe2ae1bcc26 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
> @@ -9,6 +9,7 @@
>   #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 +32,13 @@ 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);
Why doesn't this need to iterate through the physical engines of the 
virtual engine?

John.

> +	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 +60,13 @@ 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);
> +	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 a17bf0d4592b..3c173033ce23 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 dbf919801de2..e0eed70f9b92 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1550,7 +1550,12 @@ 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)
> @@ -1559,6 +1564,9 @@ 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)
> @@ -2328,8 +2336,30 @@ 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)
> @@ -2366,7 +2396,7 @@ 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 ef7e6a698e8a..dd530ae028e0 100644
> --- a/drivers/gpu/drm/i915/intel_wakeref.h
> +++ b/drivers/gpu/drm/i915/intel_wakeref.h
> @@ -124,6 +124,12 @@ 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
> @@ -171,6 +177,12 @@ 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