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

[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?

> 
> 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);
>