Re: [Intel-gfx] [PATCH v3 1/2] drm/i915: Use the correct IRQ during resume

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jun 30, 2021 at 11:52:27AM +0200, Thomas Zimmermann wrote:
> The code in xcs_resume() probably didn't work as intended. It uses
> struct drm_device.irq, which is allocated to 0, but never initialized
> by i915 to the device's interrupt number.
> 
> v3:
> 	* also use intel_synchronize_hardirq() at another callsite
> v2:
> 	* wrap irq code in intel_synchronize_hardirq() (Ville)
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 536f77b1caa0 ("drm/i915/gt: Call stop_ring() from ring resume, again")
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c       | 2 +-
>  drivers/gpu/drm/i915/gt/intel_ring_submission.c | 2 +-
>  drivers/gpu/drm/i915/i915_irq.c                 | 5 +++++
>  drivers/gpu/drm/i915/i915_irq.h                 | 1 +
>  4 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 88694822716a..5ca3d1664335 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -1229,7 +1229,7 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
>  		return true;
>  
>  	/* Waiting to drain ELSP? */
> -	synchronize_hardirq(to_pci_dev(engine->i915->drm.dev)->irq);
> +	intel_synchronize_hardirq(engine->i915);
>  	intel_engine_flush_submission(engine);
>  
>  	/* ELSP is empty, but there are ready requests? E.g. after reset */
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index 5d42a12ef3d6..1b5a22a83db6 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -185,7 +185,7 @@ static int xcs_resume(struct intel_engine_cs *engine)
>  		     ring->head, ring->tail);
>  
>  	/* Double check the ring is empty & disabled before we resume */
> -	synchronize_hardirq(engine->i915->drm.irq);
> +	intel_synchronize_hardirq(engine->i915);
>  	if (!stop_ring(engine))
>  		goto err;
>  
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 7d0ce8b9f8ed..2203dca19895 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -4575,3 +4575,8 @@ void intel_synchronize_irq(struct drm_i915_private *i915)
>  {
>  	synchronize_irq(to_pci_dev(i915->drm.dev)->irq);
>  }
> +
> +void intel_synchronize_hardirq(struct drm_i915_private *i915)
> +{
> +	synchronize_hardirq(to_pci_dev(i915->drm.dev)->irq);

I honestly think the hardirq here is about as much cargo-culted as using
the wrong irq number.

I'd just use intel_synchronize_irq in both places and see whether CI
complains, then go with that.
-Daniel

> +}
> diff --git a/drivers/gpu/drm/i915/i915_irq.h b/drivers/gpu/drm/i915/i915_irq.h
> index db34d5dbe402..e43b6734f21b 100644
> --- a/drivers/gpu/drm/i915/i915_irq.h
> +++ b/drivers/gpu/drm/i915/i915_irq.h
> @@ -94,6 +94,7 @@ void intel_runtime_pm_disable_interrupts(struct drm_i915_private *dev_priv);
>  void intel_runtime_pm_enable_interrupts(struct drm_i915_private *dev_priv);
>  bool intel_irqs_enabled(struct drm_i915_private *dev_priv);
>  void intel_synchronize_irq(struct drm_i915_private *i915);
> +void intel_synchronize_hardirq(struct drm_i915_private *i915);
>  
>  int intel_get_crtc_scanline(struct intel_crtc *crtc);
>  void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv,
> -- 
> 2.32.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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