[Intel-gfx] [PATCH] drm/i915: Only unmask required PM interrupts

[Azad, Vinit]

Our interrupt handler isn't being fired since we do set the IER bits properly (IIR bits aren't set). The overhead isn't because our driver is reacting to these interrupts, but because hardware keeps generating internal messages when PMINTRMSK doesn't mask out the up/down EI interrupts (which happen periodically).

Unfortunately, the default value of PMINTRMSK register is 0 instead of 0xFFFFFFFF as it is for other IMR, so we have to mask out the interrupts manually.

-----Original Message-----
From: daniel.vetter at ffwll.ch [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
Sent: Wednesday, August 14, 2013 13:47
To: Azad, Vinit
Cc: intel-gfx
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Only unmask required PM interrupts

On Wed, Aug 14, 2013 at 10:34 PM, Vinit Azad <vinit.azad at intel.com> wrote:
> Un-masking all PM interrupts causes hardware to generate interrupts 
> regardless of whether the interrupts are enabled on the DE side. Since 
> turbo only need up/down threshold and
> rc6 timeout interrupt, mask all other interrupts bits to avoid 
> unnecessary overhead/wake up.

Just to clarify since I can't really believe this yet: Even though we disable all other interrupt sources in PMIER and mask them in PMIMR hw still manages to fire off our interrupt handler? Do those interrupts end up setting PMIIR?

Thanks, Daniel
>
> Change-Id: I6c947df6fd5f60584d39b9e8b8c89faa51a5e827
> Signed-off-by: Vinit Azad <vinit.azad at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c 
> b/drivers/gpu/drm/i915/intel_pm.c index 8e9ce07..17a0dae 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3328,8 +3328,8 @@ static void gen6_enable_rps(struct drm_device *dev)
>         I915_WRITE(GEN6_PMIMR, I915_READ(GEN6_PMIMR) & ~GEN6_PM_RPS_EVENTS);
>         I915_WRITE(GEN6_PMIIR, GEN6_PM_RPS_EVENTS);
>         spin_unlock_irq(&dev_priv->rps.lock);
> -       /* unmask all PM interrupts */
> -       I915_WRITE(GEN6_PMINTRMSK, 0);
> +       /* only unmask PM interrupts we need. Mask all others. */
> +       I915_WRITE(GEN6_PMINTRMSK, ~GEN6_PM_RPS_EVENTS);
>
>         rc6vids = 0;
>         ret = sandybridge_pcode_read(dev_priv, 
> GEN6_PCODE_READ_RC6VIDS, &rc6vids); @@ -3596,8 +3596,8 @@ static void valleyview_enable_rps(struct drm_device *dev)
>         WARN_ON(dev_priv->rps.pm_iir != 0);
>         I915_WRITE(GEN6_PMIMR, 0);
>         spin_unlock_irq(&dev_priv->rps.lock);
> -       /* enable all PM interrupts */
> -       I915_WRITE(GEN6_PMINTRMSK, 0);
> +       /* enable only the PM interrupts we need. Mask everything else */
> +       I915_WRITE(GEN6_PMINTRMSK, ~GEN6_PM_RPS_EVENTS);
>
>         gen6_gt_force_wake_put(dev_priv);  }
> --
> 1.7.9.5
>
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> http://lists.freedesktop.org/mailman/listinfo/intel-gfx



--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch