Re: [PATCH 2/3] drm/i915/skl: Restore pipe interrupt registers after power well enabling

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Mar 02, 2015 at 03:37:47PM -0300, Paulo Zanoni wrote:
> 2015-02-13 17:37 GMT-02:00 Damien Lespiau <damien.lespiau@intel.com>:
> > The pipe interrupt registers are in the actual pipe power well, so we
> > need to restore them when re-enable the corresponding power well.
> >
> > I've also copied what we do on HSW/BDW for VGA, even if the we haven't
> > enabled unclaimed registers just yet.
> >
> > Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_irq.c         |  4 ++++
> >  drivers/gpu/drm/i915/intel_runtime_pm.c | 31 +++++++++++++++++++++++++++++++
> >  2 files changed, 35 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 65fe9e7..292ba89 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -3235,6 +3235,10 @@ void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv,
> >         uint32_t extra_ier = GEN8_PIPE_VBLANK | GEN8_PIPE_FIFO_UNDERRUN;
> >
> >         spin_lock_irq(&dev_priv->irq_lock);
> > +       if (pipe_mask & 1 << PIPE_A)
> > +               GEN8_IRQ_INIT_NDX(DE_PIPE, PIPE_A,
> > +                                 dev_priv->de_irq_mask[PIPE_A],
> > +                                 ~dev_priv->de_irq_mask[PIPE_A] | extra_ier);
> >         if (pipe_mask & 1 << PIPE_B)
> >                 GEN8_IRQ_INIT_NDX(DE_PIPE, PIPE_B,
> >                                   dev_priv->de_irq_mask[PIPE_B],
> > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > index 35e0cb6..8989747 100644
> > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > @@ -199,6 +199,34 @@ static void hsw_power_well_post_enable(struct drm_i915_private *dev_priv)
> >                                                 1 << PIPE_C | 1 << PIPE_B);
> >  }
> >
> > +static void skl_power_well_post_enable(struct drm_i915_private *dev_priv,
> > +                                      struct i915_power_well *power_well)
> > +{
> > +       struct drm_device *dev = dev_priv->dev;
> > +
> > +       /*
> > +        * After we re-enable the power well, if we touch VGA register 0x3d5
> > +        * we'll get unclaimed register interrupts. This stops after we write
> > +        * anything to the VGA MSR register. The vgacon module uses this
> > +        * register all the time, so if we unbind our driver and, as a
> > +        * consequence, bind vgacon, we'll get stuck in an infinite loop at
> > +        * console_unlock(). So make here we touch the VGA MSR register, making
> > +        * sure vgacon can keep working normally without triggering interrupts
> > +        * and error messages.
> > +        */
> > +       if (power_well->data == SKL_DISP_PW_2) {
> > +               vga_get_uninterruptible(dev->pdev, VGA_RSRC_LEGACY_IO);
> > +               outb(inb(VGA_MSR_READ), VGA_MSR_WRITE);
> > +               vga_put(dev->pdev, VGA_RSRC_LEGACY_IO);
> > +
> > +               gen8_irq_power_well_post_enable(dev_priv,
> > +                                               1 << PIPE_C | 1 << PIPE_B);
> > +       }
> > +
> > +       if (power_well->data == SKL_DISP_PW_1)
> > +               gen8_irq_power_well_post_enable(dev_priv, 1 << PIPE_A);
> > +}
> > +
> >  static void hsw_set_power_well(struct drm_i915_private *dev_priv,
> >                                struct i915_power_well *power_well, bool enable)
> >  {
> > @@ -359,6 +387,9 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
> >                                 DRM_ERROR("PG2 distributing status timeout\n");
> >                 }
> >         }
> > +
> > +       if (enable)
> > +               skl_power_well_post_enable(dev_priv, power_well);
> 
> Please take a look at "drm/i915: only run hsw_power_well_post_enable
> when really needed": http://patchwork.freedesktop.org/patch/34764/ and
> please do the equivalent change here. I also won't complain if you
> create "is_enabled" and "enable_requested" variables on
> skl_set_power_well, just like we have for hsw_set_power_well.

tbh I wonder whether we should move the irq enable/disable into the crtc
enable/disable functions on gen8+. That would have avoided the "have we
enabled this already" logic, which tends to be fragile in general. Otoh
this works too.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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