[Intel-gfx] [PATCH v4] drm/i915: Only run execlist context-switch handler after an interrupt

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Mark when we run the execlist tasklet following the interrupt, so we
> don't probe a potentially uninitialised register when submitting the
> contexts multiple times before the hardware responds.
>
> v2: Use a shared engine->irq_posted
> v3: Always use locked bitops to be sure of atomicity wrt to other bits
> in the mask.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com

Missing '>' from Cc.

Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>

> ---
>  drivers/gpu/drm/i915/i915_irq.c         | 7 +++++--
>  drivers/gpu/drm/i915/intel_lrc.c        | 3 ++-
>  drivers/gpu/drm/i915/intel_ringbuffer.h | 1 +
>  3 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 7e087c344265..3f3c9082b0f8 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1349,8 +1349,11 @@ gen8_cs_irq_handler(struct intel_engine_cs *engine, u32 iir, int test_shift)
>  {
>  	if (iir & (GT_RENDER_USER_INTERRUPT << test_shift))
>  		notify_ring(engine);
> -	if (iir & (GT_CONTEXT_SWITCH_INTERRUPT << test_shift))
> -		tasklet_schedule(&engine->irq_tasklet);
> +
> +	if (iir & (GT_CONTEXT_SWITCH_INTERRUPT << test_shift)) {
> +		set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
> +		tasklet_hi_schedule(&engine->irq_tasklet);
> +	}
>  }
>  
>  static irqreturn_t gen8_gt_irq_ack(struct drm_i915_private *dev_priv,
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 9896027880ea..f729568e5e54 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -564,7 +564,7 @@ static void intel_lrc_irq_handler(unsigned long data)
>  
>  	intel_uncore_forcewake_get(dev_priv, engine->fw_domains);
>  
> -	if (!execlists_elsp_idle(engine)) {
> +	while (test_and_clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted)) {
>  		u32 __iomem *csb_mmio =
>  			dev_priv->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine));
>  		u32 __iomem *buf =
> @@ -1297,6 +1297,7 @@ static int gen8_init_common_ring(struct intel_engine_cs *engine)
>  	DRM_DEBUG_DRIVER("Execlists enabled for %s\n", engine->name);
>  
>  	/* After a GPU reset, we may have requests to replay */
> +	clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
>  	if (!execlists_elsp_idle(engine)) {
>  		engine->execlist_port[0].count = 0;
>  		engine->execlist_port[1].count = 0;
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index a9ea84ea3155..8e872730f8eb 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -213,6 +213,7 @@ struct intel_engine_cs {
>  
>  	unsigned long irq_posted;
>  #define ENGINE_IRQ_BREADCRUMB 0
> +#define ENGINE_IRQ_EXECLIST 1
>  
>  	/* Rather than have every client wait upon all user interrupts,
>  	 * with the herd waking after every interrupt and each doing the
> -- 
> 2.11.0
>
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