[Intel-gfx] [PATCH i-g-t] pm_rps: Extended testcases with checking PMINTRMSK register value

[Chris Wilson]

Quoting Arkadiusz Hiler (2017-08-21 10:42:25)
> On Mon, Aug 21, 2017 at 08:05:58AM +0000, Dec, Katarzyna wrote:
> > I understand we do not want to check registers in IGT tests. What
> > about reading interrupt masks from debugfs (i915_frequency_info).
> 
> Hey Kasia
> 
> It would be pretty much the same thing, but instead of us reading the
> PMINTRMASK directly we would ask the kernel to do that on our behalf.
> 
> That would just hide register read, not get rid of it.
> 
> 
> I think you are missing the point. The idea is that we do not want to
> test details of in-kernel implementation, not ban the register reads
> completely.
> 
> Reading register directly, especially just to make sure that the kernel
> set something correctly is a good indicator that we are trying to do
> just that - test the internal details.
> 
> > Would that be better approach? You guys suggested to get interested in
> > kselftests for having such checks, but I am afraid that it could be
> > too much job and we have too few hands to work.
> 
> How much of an effort would the kselftest be, since it seems that you did some
> investigation already?

It doesn't even require a whole selftest, just something like

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 448e71af4772..e83b67fe0354 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -7733,7 +7733,8 @@ void intel_suspend_gt_powersave(struct drm_i915_private *dev_priv)
        if (cancel_delayed_work_sync(&dev_priv->rps.autoenable_work))
                intel_runtime_pm_put(dev_priv);
 
-       /* gen6_rps_idle() will be called later to disable interrupts */
+       WARN_ON(I915_READ(GEN6_PMINTRMSK) !=
+               gen6_sanitize_rps_pm_mask(dev_priv, ~0));
 }
 
 void intel_sanitize_gt_powersave(struct drm_i915_private *dev_priv)

(I would say an equivalent to GEM_WARN_ON for the driver, DRV_WARN_ON, or
PM_WARN_ON?)

By testing every time we do suspend the GT (i.e. after all requests are
idle and gen6_rps_idle() should have been called, that all the
interrupts are masked.) You can make a similar assertion before waking
up, but that isn't our concern.
-Chris