Re: [PATCH 2/6] drm/i915/gt: Reorganise gen8+ interrupt handler

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Quoting Mika Kuoppala (2020-01-28 12:20:46)
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> 
> > We always use a deferred bottom-half (either tasklet or irq_work) for
> > processing the response to an interrupt which means we can recombine the
> > GT irq ack+handler into one. This simplicity is important in later
> > patches as we will need to handle and then ack multiple interrupt levels
> > before acking the GT and master interrupts.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_gt_irq.c | 70 +++++++++++---------------
> >  drivers/gpu/drm/i915/gt/intel_gt_irq.h |  3 +-
> >  drivers/gpu/drm/i915/i915_irq.c        | 10 +---
> >  3 files changed, 33 insertions(+), 50 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_irq.c b/drivers/gpu/drm/i915/gt/intel_gt_irq.c
> > index f796bdf1ed30..71873a4cafc0 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_irq.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_irq.c
> > @@ -286,59 +286,49 @@ void gen6_gt_irq_handler(struct intel_gt *gt, u32 gt_iir)
> >               gen7_parity_error_irq_handler(gt, gt_iir);
> >  }
> >  
> > -void gen8_gt_irq_ack(struct intel_gt *gt, u32 master_ctl, u32 gt_iir[4])
> > +void gen8_gt_irq_handler(struct intel_gt *gt, u32 master_ctl)
> >  {
> >       void __iomem * const regs = gt->uncore->regs;
> > +     u32 iir;
> >  
> >       if (master_ctl & (GEN8_GT_RCS_IRQ | GEN8_GT_BCS_IRQ)) {
> > -             gt_iir[0] = raw_reg_read(regs, GEN8_GT_IIR(0));
> > -             if (likely(gt_iir[0]))
> > -                     raw_reg_write(regs, GEN8_GT_IIR(0), gt_iir[0]);
> > -     }
> > -
> > -     if (master_ctl & (GEN8_GT_VCS0_IRQ | GEN8_GT_VCS1_IRQ)) {
> > -             gt_iir[1] = raw_reg_read(regs, GEN8_GT_IIR(1));
> > -             if (likely(gt_iir[1]))
> > -                     raw_reg_write(regs, GEN8_GT_IIR(1), gt_iir[1]);
> > -     }
> > -
> > -     if (master_ctl & (GEN8_GT_PM_IRQ | GEN8_GT_GUC_IRQ)) {
> > -             gt_iir[2] = raw_reg_read(regs, GEN8_GT_IIR(2));
> > -             if (likely(gt_iir[2]))
> > -                     raw_reg_write(regs, GEN8_GT_IIR(2), gt_iir[2]);
> > -     }
> > -
> > -     if (master_ctl & GEN8_GT_VECS_IRQ) {
> > -             gt_iir[3] = raw_reg_read(regs, GEN8_GT_IIR(3));
> > -             if (likely(gt_iir[3]))
> > -                     raw_reg_write(regs, GEN8_GT_IIR(3), gt_iir[3]);
> > -     }
> > -}
> > -
> > -void gen8_gt_irq_handler(struct intel_gt *gt, u32 master_ctl, u32 gt_iir[4])
> > -{
> > -     if (master_ctl & (GEN8_GT_RCS_IRQ | GEN8_GT_BCS_IRQ)) {
> > -             cs_irq_handler(gt->engine_class[RENDER_CLASS][0],
> > -                            gt_iir[0] >> GEN8_RCS_IRQ_SHIFT);
> > -             cs_irq_handler(gt->engine_class[COPY_ENGINE_CLASS][0],
> > -                            gt_iir[0] >> GEN8_BCS_IRQ_SHIFT);
> > +             iir = raw_reg_read(regs, GEN8_GT_IIR(0));
> > +             if (likely(iir)) {
> > +                     cs_irq_handler(gt->engine_class[RENDER_CLASS][0],
> > +                                    iir >> GEN8_RCS_IRQ_SHIFT);
> > +                     cs_irq_handler(gt->engine_class[COPY_ENGINE_CLASS][0],
> > +                                    iir >> GEN8_BCS_IRQ_SHIFT);
> > +                     raw_reg_write(regs, GEN8_GT_IIR(0), iir);
> > +             }
> >       }
> >  
> >       if (master_ctl & (GEN8_GT_VCS0_IRQ | GEN8_GT_VCS1_IRQ)) {
> > -             cs_irq_handler(gt->engine_class[VIDEO_DECODE_CLASS][0],
> > -                            gt_iir[1] >> GEN8_VCS0_IRQ_SHIFT);
> > -             cs_irq_handler(gt->engine_class[VIDEO_DECODE_CLASS][1],
> > -                            gt_iir[1] >> GEN8_VCS1_IRQ_SHIFT);
> > +             iir = raw_reg_read(regs, GEN8_GT_IIR(1));
> > +             if (likely(iir)) {
> > +                     cs_irq_handler(gt->engine_class[VIDEO_DECODE_CLASS][0],
> > +                                    iir >> GEN8_VCS0_IRQ_SHIFT);
> > +                     cs_irq_handler(gt->engine_class[VIDEO_DECODE_CLASS][1],
> > +                                    iir >> GEN8_VCS1_IRQ_SHIFT);
> > +                     raw_reg_write(regs, GEN8_GT_IIR(1), iir);
> > +             }
> >       }
> >  
> >       if (master_ctl & GEN8_GT_VECS_IRQ) {
> > -             cs_irq_handler(gt->engine_class[VIDEO_ENHANCEMENT_CLASS][0],
> > -                            gt_iir[3] >> GEN8_VECS_IRQ_SHIFT);
> > +             iir = raw_reg_read(regs, GEN8_GT_IIR(3));
> > +             if (likely(iir)) {
> > +                     cs_irq_handler(gt->engine_class[VIDEO_ENHANCEMENT_CLASS][0],
> > +                                    iir >> GEN8_VECS_IRQ_SHIFT);
> > +                     raw_reg_write(regs, GEN8_GT_IIR(3), iir);
> > +             }
> >       }
> >  
> >       if (master_ctl & (GEN8_GT_PM_IRQ | GEN8_GT_GUC_IRQ)) {
> > -             gen6_rps_irq_handler(&gt->rps, gt_iir[2]);
> > -             guc_irq_handler(&gt->uc.guc, gt_iir[2] >> 16);
> > +             iir = raw_reg_read(regs, GEN8_GT_IIR(2));
> > +             if (likely(iir)) {
> > +                     gen6_rps_irq_handler(&gt->rps, iir);
> > +                     guc_irq_handler(&gt->uc.guc, iir >> 16);
> > +                     raw_reg_write(regs, GEN8_GT_IIR(2), iir);
> > +             }
> >       }
> >  }
> >  
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_irq.h b/drivers/gpu/drm/i915/gt/intel_gt_irq.h
> > index 8f37593712c9..886c5cf408a2 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_irq.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_irq.h
> > @@ -36,9 +36,8 @@ void gen5_gt_enable_irq(struct intel_gt *gt, u32 mask);
> >  
> >  void gen6_gt_irq_handler(struct intel_gt *gt, u32 gt_iir);
> >  
> > -void gen8_gt_irq_ack(struct intel_gt *gt, u32 master_ctl, u32 gt_iir[4]);
> > +void gen8_gt_irq_handler(struct intel_gt *gt, u32 master_ctl);
> >  void gen8_gt_irq_reset(struct intel_gt *gt);
> > -void gen8_gt_irq_handler(struct intel_gt *gt, u32 master_ctl, u32 gt_iir[4]);
> >  void gen8_gt_irq_postinstall(struct intel_gt *gt);
> >  
> >  #endif /* INTEL_GT_IRQ_H */
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 87a6662abc1b..e40dd226fde8 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -1614,7 +1614,6 @@ static irqreturn_t cherryview_irq_handler(int irq, void *arg)
> >               u32 master_ctl, iir;
> >               u32 pipe_stats[I915_MAX_PIPES] = {};
> >               u32 hotplug_status = 0;
> > -             u32 gt_iir[4];
> >               u32 ier = 0;
> >  
> >               master_ctl = I915_READ(GEN8_MASTER_IRQ) & ~GEN8_MASTER_IRQ_CONTROL;
> > @@ -1642,7 +1641,7 @@ static irqreturn_t cherryview_irq_handler(int irq, void *arg)
> >               ier = I915_READ(VLV_IER);
> >               I915_WRITE(VLV_IER, 0);
> >  
> > -             gen8_gt_irq_ack(&dev_priv->gt, master_ctl, gt_iir);
> > +             gen8_gt_irq_handler(&dev_priv->gt, master_ctl);
> >  
> >               if (iir & I915_DISPLAY_PORT_INTERRUPT)
> >                       hotplug_status = i9xx_hpd_irq_ack(dev_priv);
> > @@ -1666,8 +1665,6 @@ static irqreturn_t cherryview_irq_handler(int irq, void *arg)
> >               I915_WRITE(VLV_IER, ier);
> >               I915_WRITE(GEN8_MASTER_IRQ, GEN8_MASTER_IRQ_CONTROL);
> >  
> > -             gen8_gt_irq_handler(&dev_priv->gt, master_ctl, gt_iir);
> > -
> >               if (hotplug_status)
> >                       i9xx_hpd_irq_handler(dev_priv, hotplug_status);
> >  
> > @@ -2396,7 +2393,6 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
> >       struct drm_i915_private *dev_priv = arg;
> >       void __iomem * const regs = dev_priv->uncore.regs;
> >       u32 master_ctl;
> > -     u32 gt_iir[4];
> >  
> >       if (!intel_irqs_enabled(dev_priv))
> >               return IRQ_NONE;
> > @@ -2408,7 +2404,7 @@ static irqreturn_t gen8_irq_handler(int irq, void *arg)
> >       }
> >  
> >       /* Find, clear, then process each source of interrupt */
> 
> /* Find, process and then clear each source of interrupt */

The order is still ack / process, and that is quite important for
allowing interrupt delivery as we process. It's just that we use
bottom-halves rather than a local deferral.

	/* Find, clear, then process (via bottom-halves) each source of interrupt */
-Chris
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