Quoting Mika Kuoppala (2018-02-08 11:43:50)
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > After we assert the reset request (and wait for 20us), when the device
> > has been fully reset it asserts the reset-status bit. Before we stop
> > requesting the reset and allow the device to return to normal, we should
> > wait for the reset to be completed. (Similar to how we wait for the
> > device to return to normal after deasserting the reset request.)
> >
> > v2: Rename i915_reset_completed() probe to not cause as much confusion.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_uncore.c | 15 +++++++++++----
> > 1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> > index 0fd59dd6bbb5..e09981a3113c 100644
> > --- a/drivers/gpu/drm/i915/intel_uncore.c
> > +++ b/drivers/gpu/drm/i915/intel_uncore.c
> > @@ -1550,24 +1550,31 @@ static void i915_stop_engines(struct drm_i915_private *dev_priv,
> > gen3_stop_engine(engine);
> > }
> >
> > -static bool i915_reset_complete(struct pci_dev *pdev)
> > +static bool i915_in_reset(struct pci_dev *pdev)
> > {
> > u8 gdrst;
> >
> > pci_read_config_byte(pdev, I915_GDRST, &gdrst);
> > - return (gdrst & GRDOM_RESET_STATUS) == 0;
> > + return gdrst & GRDOM_RESET_STATUS;
> > }
> >
> > static int i915_do_reset(struct drm_i915_private *dev_priv, unsigned engine_mask)
> > {
> > struct pci_dev *pdev = dev_priv->drm.pdev;
> > + int err;
> >
> > - /* assert reset for at least 20 usec */
> > + /* Assert reset for at least 20 usec, and wait for acknowledgement. */
> > pci_write_config_byte(pdev, I915_GDRST, GRDOM_RESET_ENABLE);
> > usleep_range(50, 200);
> > + err = wait_for(i915_in_reset(pdev), 500);
> > +
> > + /* Clear the reset request. */
> > pci_write_config_byte(pdev, I915_GDRST, 0);
> > + usleep_range(50, 200);
> > + if (!err)
> > + err = wait_for(!i915_in_reset(pdev), 500);
> >
>
> Regardless of if this helps or not with pnv, it makes the
> both phases clear.
>
> Any thoughts of starting to log the reset attempts
> with timeout, even if the subsequent reset succeeds?
>
> Patch is,
> Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Although I don't expect this pair to help CI, it feels justifiable
paranoia. Thanks for the review,
-Chris
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