Re: [PATCH 05/10] drm/i915: Mark up "sentinel" requests

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 10/10/2019 08:14, Chris Wilson wrote:
> Sometimes we want to emit a terminator request, a request that flushes
> the pipeline and allows no request to come after it. This can be used
> for a "preempt-to-idle" to ensure that upon processing the
> context-switch to that request, all other active contexts have been
> flushed.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/gt/intel_lrc.c |  6 ++++++
>   drivers/gpu/drm/i915/i915_request.h | 10 ++++++++--
>   2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index aa52e5f34dab..eb99f1e804f7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1253,6 +1253,9 @@ static bool can_merge_rq(const struct i915_request *prev,
>   	if (i915_request_completed(next))
>   		return true;
>   
> +	if (i915_request_has_sentinel(prev))
> +		return false;
> +
>   	if (!can_merge_ctx(prev->hw_context, next->hw_context))
>   		return false;
>   
> @@ -1724,6 +1727,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>   				if (last->hw_context == rq->hw_context)
>   					goto done;
>   
> +				if (i915_request_has_sentinel(last))
> +					goto done;
> +
>   				/*
>   				 * If GVT overrides us we only ever submit
>   				 * port[0], leaving port[1] empty. Note that we
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index 6a95242b280d..96991d64759c 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -216,8 +216,9 @@ struct i915_request {
>   	unsigned long emitted_jiffies;
>   
>   	unsigned long flags;
> -#define I915_REQUEST_WAITBOOST BIT(0)
> -#define I915_REQUEST_NOPREEMPT BIT(1)
> +#define I915_REQUEST_WAITBOOST	BIT(0)
> +#define I915_REQUEST_NOPREEMPT	BIT(1)
> +#define I915_REQUEST_SENTINEL	BIT(2)
>   
>   	/** timeline->request entry for this request */
>   	struct list_head link;
> @@ -440,6 +441,11 @@ static inline bool i915_request_has_nopreempt(const struct i915_request *rq)
>   	return unlikely(rq->flags & I915_REQUEST_NOPREEMPT);
>   }
>   
> +static inline bool i915_request_has_sentinel(const struct i915_request *rq)
> +{
> +	return unlikely(rq->flags & I915_REQUEST_SENTINEL);
> +}
> +
>   static inline struct intel_timeline *
>   i915_request_timeline(struct i915_request *rq)
>   {
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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