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

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

On Fri, 2014-10-17 at 16:01 -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".
> 
> v2: VLV is an exception to the early_sanitize() rule: it needs to do
> stuff before calling early_sanitize(), so instead of calling it
> earlier for every platform, we call it earlier for non-VLV by adding
> the early_sanitize() call inside intel_resume_prepare(). This doesn't
> look like the most-beautiful-solution-ever, but, well, at least it
> fixes the bug. (Imre)
> 
> 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 | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index a05a1d0..f6d28f2 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -669,7 +669,6 @@ static int i915_drm_thaw_early(struct drm_device *dev)
>  	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);
>  
> @@ -1049,6 +1048,8 @@ static int snb_resume_prepare(struct drm_i915_private *dev_priv,
>  
>  	if (rpm_resume)
>  		intel_init_pch_refclk(dev);
> +	else
> +		intel_uncore_early_sanitize(dev, true);
>  
>  	return 0;
>  }
> @@ -1056,6 +1057,9 @@ static int snb_resume_prepare(struct drm_i915_private *dev_priv,
>  static int hsw_resume_prepare(struct drm_i915_private *dev_priv,
>  				bool rpm_resume)
>  {
> +	if (!rpm_resume)
> +		intel_uncore_early_sanitize(dev_priv->dev, true);
> +
>  	hsw_disable_pc8(dev_priv);
>  
>  	return 0;
> @@ -1421,6 +1425,9 @@ static int vlv_resume_prepare(struct drm_i915_private *dev_priv,
>  		i915_gem_restore_fences(dev);
>  	}
>  
> +	if (!rpm_resume)
> +		intel_uncore_early_sanitize(dev, true);
> +
>  	return ret;
>  }
>  

You also need to call intel_uncore_early_sanitize() from
intel_resume_prepare() for the rest of the platforms. With that fixed:
Reviewed-by: Imre Deak <imre.deak@intel.com>

Looking at the result, I agree it's not the nicest, so yet another way
to reduce the clutter would be to have the following instead in
i915_drm_thaw_early():

intel_resume_early_prepare()
intel_uncore_early_sanitize()
intel_resume_prepare()

and do the early steps for VLV in intel_resume_early_prepare(). I'm ok
with both solutions.

--Imre