Re: [PATCH v2 2/2] drm/i915: fix HW lockup due to missing RPS IRQ workaround on GEN6

Imre Deak
2014-12-19T14:07:51Z

On Fri, 2014-12-19 at 14:41 +0100, Daniel Vetter wrote:
> On Fri, Dec 19, 2014 at 02:51:57PM +0200, Imre Deak wrote:
> > In
> >
> > commit dbea3cea69508e9d548ed4a6be13de35492e5d15
> > Author: Imre Deak <imre.deak@intel.com>
> > Date: Mon Dec 15 18:59:28 2014 +0200
> >
> > drm/i915: sanitize RPS resetting during GPU reset
> >
> > we disable RPS interrupts during GPU resetting, but don't apply the
> > necessary GEN6 HW workaround. This leads to a HW lockup during a
> > subsequent "looping batchbuffer" workload. This is triggered by the
> > testcase that submits exactly this kind of workload after a simulated
> > GPU reset. I'm not sure how likely the bug would have triggered
> > otherwise, since we would have applied the workaround anyway shortly
> > after the GPU reset, when enabling GT powersaving from the deferred
> > work.
> >
> > This may also fix unrelated issues, since during driver loading /
> > suspending we also disable RPS interrupts and so we also had a short
> > window during the rest of the loading / resuming where a similar
> > workload could run without the workaround applied.
> >
> > v2:
> > - separate the fix to route RPS interrupts to the CPU on GEN9 too
> > to a separate patch (Daniel)
> >
> > Bisected-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
> > Testcase: igt/gem_reset_stats/ban-ctx-render
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87429
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> > drivers/gpu/drm/i915/i915_irq.c | 18 ++++++++++++++++--
> > drivers/gpu/drm/i915/intel_drv.h | 1 +
> > drivers/gpu/drm/i915/intel_pm.c | 11 +----------
> > 3 files changed, 18 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index aa3180c..f853f26 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -296,6 +296,21 @@ void gen6_enable_rps_interrupts(struct drm_device *dev)
> > spin_unlock_irq(&dev_priv->irq_lock);
> > }
> >
> > +u32 gen6_sanitize_rps_pm_mask(struct drm_i915_private *dev_priv, u32 mask)
> > +{
> > + /*
> > + * IVB and SNB hard hangs on looping batchbuffer
> > + * if GEN6_PM_UP_EI_EXPIRED is masked.
> > + */
> > + if (INTEL_INFO(dev_priv)->gen <= 7 && !IS_HASWELL(dev_priv))
>
> Hm, the comment says snb&ivb, but the code includes byt.

Yea, that code comment is out-of-date. You want me to send a v3 fixing
that?

> We also have an unprocted write to PMINTRMSK still in vlv_set_rps_idle.
> For consistency I think we should either switch to explicitly check for
> only snb/ivb here or adapt the mask in vlv_set_rps_idle too.

gen6_rps_pm_mask() is also used for VLV, so there is only the
unprotected write you mention. But that can be fixed up separately.

> I think the later is preferrable since that's the only vlv function
> that doesn't sanitize the rps interrupts with this now. We could later
> on blow through some cycles on vlv to figure out whether it's afflicted
> from this bug or not.

> -Daniel
>
> > + mask &= ~GEN6_PM_RP_UP_EI_EXPIRED;
> > +
> > + if (INTEL_INFO(dev_priv)->gen >= 8)
> > + mask &= ~GEN8_PMINTR_REDIRECT_TO_NON_DISP;
> > +
> > + return mask;
> > +}
> > +
> > void gen6_disable_rps_interrupts(struct drm_device *dev)
> > {
> > struct drm_i915_private *dev_priv = dev->dev_private;
> > @@ -308,8 +323,7 @@ void gen6_disable_rps_interrupts(struct drm_device *dev)
> >
> > spin_lock_irq(&dev_priv->irq_lock);
> >
> > - I915_WRITE(GEN6_PMINTRMSK, INTEL_INFO(dev_priv)->gen >= 8 ?
> > - ~GEN8_PMINTR_REDIRECT_TO_NON_DISP : ~0);
> > + I915_WRITE(GEN6_PMINTRMSK, gen6_sanitize_rps_pm_mask(dev_priv, ~0));
> >
> > __gen6_disable_pm_irq(dev_priv, dev_priv->pm_rps_events);
> > I915_WRITE(gen6_pm_ier(dev_priv), I915_READ(gen6_pm_ier(dev_priv)) &
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index 588b618..bb871f3 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -795,6 +795,7 @@ void gen6_disable_pm_irq(struct drm_i915_private *dev_priv, uint32_t mask);
> > void gen6_reset_rps_interrupts(struct drm_device *dev);
> > void gen6_enable_rps_interrupts(struct drm_device *dev);
> > void gen6_disable_rps_interrupts(struct drm_device *dev);
> > +u32 gen6_sanitize_rps_pm_mask(struct drm_i915_private *dev_priv, u32 mask);
> > void intel_runtime_pm_disable_interrupts(struct drm_i915_private *dev_priv);
> > void intel_runtime_pm_enable_interrupts(struct drm_i915_private *dev_priv);
> > static inline bool intel_irqs_enabled(struct drm_i915_private *dev_priv)
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index f1f06d7..4bd1b8b 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3745,16 +3745,7 @@ static u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val)
> > mask |= dev_priv->pm_rps_events & (GEN6_PM_RP_DOWN_EI_EXPIRED | GEN6_PM_RP_UP_EI_EXPIRED);
> > mask &= dev_priv->pm_rps_events;
> >
> > - /* IVB and SNB hard hangs on looping batchbuffer
> > - * if GEN6_PM_UP_EI_EXPIRED is masked.
> > - */
> > - if (INTEL_INFO(dev_priv->dev)->gen <= 7 && !IS_HASWELL(dev_priv->dev))
> > - mask |= GEN6_PM_RP_UP_EI_EXPIRED;
> > -
> > - if (INTEL_INFO(dev_priv)->gen >= 8)
> > - mask |= GEN8_PMINTR_REDIRECT_TO_NON_DISP;
> > -
> > - return ~mask;
> > + return gen6_sanitize_rps_pm_mask(dev_priv, ~mask);
> > }
> >
> > /* gen6_set_rps is called to update the frequency request, but should also be
> > --
> > 1.8.4
> >
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