Re: [PATCH v6] drm/i915: Apply missed interrupt after reset w/a to all ringbuffer gen

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

On Mon, Dec 17, 2018 at 06:07:45PM +0000, Chris Wilson wrote:
> Quoting Ville Syrjälä (2018-12-17 18:02:25)
> > On Mon, Dec 17, 2018 at 03:20:55PM +0000, Chris Wilson wrote:
> > > Having completed a test run of gem_eio across all machines in CI we also
> > > observe the phenomenon (of lost interrupts after resetting the GPU) on
> > > gen3 machines as well as the previously sighted gen6/gen7. Let's apply
> > > the same HWSTAM workaround that was effective for gen6+ for all, as
> > > although we haven't seen the same failure on gen4/5 it seems prudent to
> > > keep the code the same.
> > > 
> > > As a consequence we can remove the extra setting of HWSTAM and apply the
> > > register from a single site.
> > > 
> > > v2: Delazy and move the HWSTAM into its own function
> > > v3: Mask off all HWSP writes on driver unload and engine cleanup.
> > > v4: And what about the physical hwsp?
> > > v5: No, engine->init_hw() is not called from driver_init_hw(), don't be
> > > daft. Really scrub HWSTAM as early as we can in driver_init_mmio()
> > > v6: Rename set_hwsp as it was setting the mask not the hwsp register.
> > > 
> > > References: https://bugs.freedesktop.org/show_bug.cgi?id=108735
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_irq.c         |   9 --
> > >  drivers/gpu/drm/i915/intel_engine_cs.c  |  23 +++++
> > >  drivers/gpu/drm/i915/intel_ringbuffer.c | 107 +++++++++++++++---------
> > >  3 files changed, 91 insertions(+), 48 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > > index e2dac9b5f4ce..0c7fc9890891 100644
> > > --- a/drivers/gpu/drm/i915/i915_irq.c
> > > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > > @@ -3586,9 +3586,6 @@ static void ironlake_irq_reset(struct drm_device *dev)
> > >  {
> > >       struct drm_i915_private *dev_priv = to_i915(dev);
> > >  
> > > -     if (IS_GEN(dev_priv, 5))
> > > -             I915_WRITE(HWSTAM, 0xffffffff);
> > > -
> > >       GEN3_IRQ_RESET(DE);
> > >       if (IS_GEN(dev_priv, 7))
> > >               I915_WRITE(GEN7_ERR_INT, 0xffffffff);
> > > @@ -4368,8 +4365,6 @@ static void i8xx_irq_reset(struct drm_device *dev)
> > >  
> > >       i9xx_pipestat_irq_reset(dev_priv);
> > >  
> > > -     I915_WRITE16(HWSTAM, 0xffff);
> > > -
> > >       GEN2_IRQ_RESET();
> > >  }
> > >  
> > > @@ -4537,8 +4532,6 @@ static void i915_irq_reset(struct drm_device *dev)
> > >  
> > >       i9xx_pipestat_irq_reset(dev_priv);
> > >  
> > > -     I915_WRITE(HWSTAM, 0xffffffff);
> > > -
> > >       GEN3_IRQ_RESET();
> > >  }
> > >  
> > > @@ -4648,8 +4641,6 @@ static void i965_irq_reset(struct drm_device *dev)
> > >  
> > >       i9xx_pipestat_irq_reset(dev_priv);
> > >  
> > > -     I915_WRITE(HWSTAM, 0xffffffff);
> > > -
> > >       GEN3_IRQ_RESET();
> > >  }
> > >  
> > > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> > > index 6f165f9ad2bf..f1a2aeb34e5e 100644
> > > --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> > > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> > > @@ -261,6 +261,23 @@ static void __sprint_engine_name(char *name, const struct engine_info *info)
> > >                        info->instance) >= INTEL_ENGINE_CS_MAX_NAME);
> > >  }
> > >  
> > > +static void set_hwsp_writemask(struct intel_engine_cs *engine, u32 mask)
> > > +{
> > > +     struct drm_i915_private *dev_priv = engine->i915;
> > > +     i915_reg_t hwstam = RING_HWSTAM(engine->mmio_base);
> > 
> > g4x/ilk don't have HWSTAM for the bsd. A quick test on my ilk shows that
> > the register at that offset stays at 0x0 even if written, so it might
> > even be safe. But maybe we shouldn't poke at things that aren't there?
> 
> Swines. Did they forget where the copy function was? Or did they use the
> one mask for both status pages? Probably just don't maintain a copy of
> the iir in hwsp/bsd.

Not sure. Morbid curiosity might force me to find out one day.

-- 
Ville Syrjälä
Intel
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