[Intel-gfx] [PATCH 06/11] drm/i915/tdr: Restart submission after engine reset

[Chris Wilson]

On Tue, Jul 26, 2016 at 05:40:52PM +0100, Arun Siluvery wrote:
> We stop the engine during reset and recovery so after a successful reset
> the request that caused the hang would've been removed from the queue so we
> can now restart submissions to elsp.
> 
> 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/intel_lrc.c | 45 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 42 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 8fc5a3b..7834edc 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -418,7 +418,8 @@ static inline void execlists_context_status_change(
>  	atomic_notifier_call_chain(&rq->ctx->status_notifier, status, rq);
>  }
>  
> -static void execlists_context_unqueue(struct intel_engine_cs *engine)
> +static void execlists_context_unqueue(struct intel_engine_cs *engine,
> +				      bool submission_after_reset)
>  {
>  	struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
>  	struct drm_i915_gem_request *cursor, *tmp;
> @@ -436,6 +437,27 @@ static void execlists_context_unqueue(struct intel_engine_cs *engine)
>  				 execlist_link) {
>  		if (!req0) {
>  			req0 = cursor;
> +
> +			/*
> +			 * we submit two requests at a time, req0 and req1.
> +			 * Assume that req0 is the one that causes hang and
> +			 * req1 is a normal batch.
> +
> +			 * After engine reset, once engine is
> +			 * reinitialized, we skip req0 and submit req1
> +			 * along with next request in the queue so we endup
> +			 * incrementing req1->elsp_submitted again. But
> +			 * after reset HW would've switched to req1 and
> +			 * executed it so just this once, submit only req1
> +			 * (which is req0 now) and don't increment
> +			 * submission count. Once this is removed we submit
> +			 * two requests as usual.
> +			 */
> +			if (submission_after_reset) {
> +				if (req0->elsp_submitted)
> +					req0->elsp_submitted--;
> +				break;

And no. Put the special case handling in the reset to cancel the
submitted hw tracking and re-establish the request queue.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre