Re: [PATCH 5/5] drm/i915: Improve irq handling after gpu resets

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, May 22, 2014 at 05:56:35PM +0200, Daniel Vetter wrote:
> Currently we do a full re-init of all interrupts after a gpu hang.
> Which is pretty bad since we don't restore the interrupts we've
> enabled at runtime correctly. Even with that addressed it's rather
> horribly race.
> 
> But on g4x and later we only reset the gt and not the entire gpu.
> Which means we only need to reset the GT interrupt bits. Which has the
> nice benefit that vblank waits, pipe CRC interrupts and everything
> else display related just keeps on working.
> 
> The downside is that gt interrupt handling (i.e. ring->get/put_irq) is
> still racy. But as long as the gpu hang reliably wakes all waters and
> we have a short time where the refcount drops to 0 we'll recover. So
> not that bad really.

A quick test on IVB tells me that GTIMR and GEN6_PMIMR survive the full
gt reset. But the ring IMRs do get clobbered. So could we just skip the
entire irq reset here?

> 
> Testcase: igt/kms_flip/vblank-vs-hang
> Testcase: igt/kms_pipe_crc_basic/hang-*
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_drv.c | 17 +++++++++--------
>  drivers/gpu/drm/i915/i915_drv.h |  1 +
>  drivers/gpu/drm/i915/i915_irq.c | 35 +++++++++++++++++++++++++++--------
>  3 files changed, 37 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index c83c83b74bf4..69a75bb7ad83 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -811,17 +811,18 @@ int i915_reset(struct drm_device *dev)
>  		}
>  
>  		/*
> -		 * FIXME: This is horribly race against concurrent pageflip and
> -		 * vblank wait ioctls since they can observe dev->irqs_disabled
> -		 * being false when they shouldn't be able to.
> +		 * FIXME: This races pretty badly against concurrent holders of
> +		 * ring interrupts. This is possible since we've started to drop
> +		 * dev->struct_mutex in select places when waiting for the gpu.
>  		 */
> -		drm_irq_uninstall(dev);
> -		drm_irq_install(dev, dev->pdev->irq);
> +		intel_gt_irq_reinit(dev);
>  
> -		/* rps/rc6 re-init is necessary to restore state lost after the
> -		 * reset and the re-install of drm irq. Skip for ironlake per
> +		/*
> +		 * rps/rc6 re-init is necessary to restore state lost after the
> +		 * reset and the re-install of gt irqs. Skip for ironlake per
>  		 * previous concerns that it doesn't respond well to some forms
> -		 * of re-init after reset. */
> +		 * of re-init after reset.
> +		 */
>  		if (INTEL_INFO(dev)->gen > 5)
>  			intel_reset_gt_powersave(dev);
>  
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 459b02ad1ef3..61792c4050e7 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2078,6 +2078,7 @@ void gen6_set_pm_mask(struct drm_i915_private *dev_priv, u32 pm_iir,
>  							int new_delay);
>  extern void intel_irq_init(struct drm_device *dev);
>  extern void intel_hpd_init(struct drm_device *dev);
> +extern void intel_gt_irq_reinit(struct drm_device *dev);
>  
>  extern void intel_uncore_sanitize(struct drm_device *dev);
>  extern void intel_uncore_early_sanitize(struct drm_device *dev);
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 3cd659b47dd2..6dba645a81fa 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -3140,6 +3140,14 @@ static void valleyview_irq_preinstall(struct drm_device *dev)
>  	POSTING_READ(VLV_IER);
>  }
>  
> +static void gen8_gt_irq_reset(struct drm_i915_private *dev_priv)
> +{
> +	GEN8_IRQ_RESET_NDX(GT, 0);
> +	GEN8_IRQ_RESET_NDX(GT, 1);
> +	GEN8_IRQ_RESET_NDX(GT, 2);
> +	GEN8_IRQ_RESET_NDX(GT, 3);
> +}
> +
>  static void gen8_irq_reset(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -3148,10 +3156,7 @@ static void gen8_irq_reset(struct drm_device *dev)
>  	I915_WRITE(GEN8_MASTER_IRQ, 0);
>  	POSTING_READ(GEN8_MASTER_IRQ);
>  
> -	GEN8_IRQ_RESET_NDX(GT, 0);
> -	GEN8_IRQ_RESET_NDX(GT, 1);
> -	GEN8_IRQ_RESET_NDX(GT, 2);
> -	GEN8_IRQ_RESET_NDX(GT, 3);
> +	gen8_gt_irq_reset(dev_priv);
>  
>  	for_each_pipe(pipe)
>  		GEN8_IRQ_RESET_NDX(DE_PIPE, pipe);
> @@ -3171,10 +3176,7 @@ static void cherryview_irq_preinstall(struct drm_device *dev)
>  	I915_WRITE(GEN8_MASTER_IRQ, 0);
>  	POSTING_READ(GEN8_MASTER_IRQ);
>  
> -	GEN8_IRQ_RESET_NDX(GT, 0);
> -	GEN8_IRQ_RESET_NDX(GT, 1);
> -	GEN8_IRQ_RESET_NDX(GT, 2);
> -	GEN8_IRQ_RESET_NDX(GT, 3);
> +	gen8_gt_irq_reset(dev_priv);
>  
>  	GEN5_IRQ_RESET(GEN8_PCU_);
>  
> @@ -4436,6 +4438,23 @@ void intel_hpd_init(struct drm_device *dev)
>  	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
>  }
>  
> +void intel_gt_irq_reinit(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +
> +	spin_lock_irq(&dev_priv->irq_lock);
> +	if (INTEL_INFO(dev)->gen >= 8) {
> +		gen8_gt_irq_reset(dev_priv);
> +		gen8_gt_irq_postinstall(dev_priv);
> +	} else if (INTEL_INFO(dev)->gen >= 5) {
> +		gen5_gt_irq_reset(dev);
> +		gen5_gt_irq_postinstall(dev);
> +	} else {
> +		WARN_ON(!IS_G4X(dev));
> +	}
> +	spin_unlock_irq(&dev_priv->irq_lock);
> +}
> +
>  /* Disable interrupts so we can allow runtime PM. */
>  void intel_runtime_pm_disable_interrupts(struct drm_device *dev)
>  {
> -- 
> 1.8.4.rc3
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC