Re: [PATCH] drm/i915: run intel_uncore_early_sanitize earlier on resume

[Imre Deak <imre.deak@intel.com>]

On Wed, 2014-10-15 at 16:07 -0300, Paulo Zanoni wrote:
> 2014-10-10 8:25 GMT-03:00 Imre Deak <imre.deak@intel.com>:
> > On Thu, 2014-10-09 at 14:46 -0300, Paulo Zanoni wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> >>
> >> As far as I understand, intel_uncore_early_sanitize() was supposed to
> >> be ran before any register access, but currently
> >> intel_resume_prepare() is ran earlier, and it does register
> >> access. I don't think it should be safe to be calling
> >> I915_{READ,WRITE} without calling intel_uncore_early_sanitize() first.
> >>
> >> One of the problems we currently have is that when we suspend/resume
> >> BDW, the FPGA_DBG_RM_NOCLAIM bit becomes 1, so we end up printing an
> >> "unclaimed register" message on resume, but this message doesn't
> >> really seem to have been triggered by our driver or user space, since
> >> the bit was not there before suspending, and gets there just after
> >> resuming, before any of our own register accesses. So calling
> >> intel_uncore_early_sanitize() as a first thing will allow us to stop
> >> printing the error message, fixing the "bug".
> >
> > One issue is that intel_uncore_early_sanitize() uses forcewake, which is
> > enabled only in prepare resume for VLV (vlv_allow_gt_wake()). Maybe
> > FPGA_DBG could be reset separately before the rest?
> 
> It doesn't "use" forcewake, it calls intel_uncore_forcewake_reset().

Hm, right I only remembered that because of

"drm/i915: check for GT faults during S3 resume and S4 restore too"

on the mailing list, but it's not yet merged. 

> Shouldn't we move the vlv code (e.g., vlv_allow_gt_wake()) to inside
> intel_uncore_forcewake_reset() instead?
>
> To my understanding, it doesn't make sense to call anything at all
> before intel_uncore_early_sanitize()...

On VLV we need to do the steps in the resume_prepare handler first. Also
we don't want to call vlv_allow_gt_wake() during driver init. But yes, I
see that for other platforms it makes sense to move
intel_uncore_early_sanitize() earlier. One way would be to call it from
resume_prepare for each platform at the proper place in case of system
resume.

> >
> >>
> >> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> >> Cc: Imre Deak <imre.deak@intel.com>
> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83094
> >> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_drv.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> Maybe we need to move even more code up?
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> >> index a05a1d0..dffb173 100644
> >> --- a/drivers/gpu/drm/i915/i915_drv.c
> >> +++ b/drivers/gpu/drm/i915/i915_drv.c
> >> @@ -665,11 +665,11 @@ static int i915_drm_thaw_early(struct drm_device *dev)
> >>       struct drm_i915_private *dev_priv = dev->dev_private;
> >>       int ret;
> >>
> >> +     intel_uncore_early_sanitize(dev, true);
> >>       ret = intel_resume_prepare(dev_priv, false);
> >>       if (ret)
> >>               DRM_ERROR("Resume prepare failed: %d,Continuing resume\n", ret);
> >>
> >> -     intel_uncore_early_sanitize(dev, true);
> >>       intel_uncore_sanitize(dev);
> >>       intel_power_domains_init_hw(dev_priv);
> >>
> >
> >
> 
> 
>