Re: [PATCH 1/3] drm/i915: Use intel_engine_stop_cs when stopping ringbuffer

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Mika Kuoppala <mika.kuoppala@linux.intel.com> writes:

> We have an exported function for stopping the engine before
> disabling a ringbuffer. Take it into use.
>
> v2: use fw on empty check
>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_engine_cs.c  |  3 ++
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 41 ++++++++++++++-----------
>  2 files changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index df8f88142f1d..e35dc0386bf6 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -856,6 +856,9 @@ void intel_engine_cancel_stop_cs(struct intel_engine_cs *engine)
>  {
>  	struct drm_i915_private *dev_priv = engine->i915;
>  
> +	if (INTEL_GEN(dev_priv) < 3)
> +		return;
> +
>  	GEM_TRACE("%s\n", engine->name);
>  
>  	I915_WRITE_FW(RING_MI_MODE(engine->mmio_base),
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 1b96b0960adc..d7486f9a29a9 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -604,26 +604,32 @@ static void ring_setup_status_page(struct intel_engine_cs *engine)
>  	flush_cs_tlb(engine);
>  }
>  
> +static bool ring_is_empty(struct intel_engine_cs *engine)
> +{
> +	struct drm_i915_private *dev_priv = engine->i915;
> +	const u32 base = engine->mmio_base;
> +
> +	return (I915_READ_FW(RING_HEAD(base)) & HEAD_ADDR) ==
> +		(I915_READ_FW(RING_HEAD(base)) & TAIL_ADDR);

ARgh!
-Mika

> +}
> +
>  static bool stop_ring(struct intel_engine_cs *engine)
>  {
>  	struct drm_i915_private *dev_priv = engine->i915;
> +	int ret;
>  
> -	if (INTEL_GEN(dev_priv) > 2) {
> -		I915_WRITE_MODE(engine, _MASKED_BIT_ENABLE(STOP_RING));
> -		if (intel_wait_for_register(dev_priv,
> -					    RING_MI_MODE(engine->mmio_base),
> -					    MODE_IDLE,
> -					    MODE_IDLE,
> -					    1000)) {
> -			DRM_ERROR("%s : timed out trying to stop ring\n",
> -				  engine->name);
> -			/* Sometimes we observe that the idle flag is not
> -			 * set even though the ring is empty. So double
> -			 * check before giving up.
> -			 */
> -			if (I915_READ_HEAD(engine) != I915_READ_TAIL(engine))
> -				return false;
> -		}
> +	ret = intel_engine_stop_cs(engine);
> +	if (ret == -ENODEV)
> +		ret = 0;
> +
> +	if (ret) {
> +		/*
> +		 * Sometimes we observe that the idle flag is not
> +		 * set even though the ring is empty. So double
> +		 * check before giving up.
> +		 */
> +		if (!ring_is_empty(engine))
> +			return false;
>  	}
>  
>  	I915_WRITE_HEAD(engine, I915_READ_TAIL(engine));
> @@ -718,8 +724,7 @@ static int init_ring_common(struct intel_engine_cs *engine)
>  		goto out;
>  	}
>  
> -	if (INTEL_GEN(dev_priv) > 2)
> -		I915_WRITE_MODE(engine, _MASKED_BIT_DISABLE(STOP_RING));
> +	intel_engine_cancel_stop_cs(engine);
>  
>  	/* Now awake, let it get started */
>  	if (ring->tail != ring->head) {
> -- 
> 2.17.1
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