[Intel-gfx] [PATCH] drm/i915: Undo gtt scratch pte unmapping again

[Takashi Iwai]

At Wed, 26 Mar 2014 20:10:09 +0100,
Daniel Vetter wrote:
> 
> It apparently blows up on some machines. This functionally reverts
> 
> commit 828c79087cec61eaf4c76bb32c222fbe35ac3930
> Author: Ben Widawsky <benjamin.widawsky at intel.com>
> Date:   Wed Oct 16 09:21:30 2013 -0700
> 
>     drm/i915: Disable GGTT PTEs on GEN6+ suspend
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=64841
> Reported-and-Tested-by: Brad  Jackson <bjackson0971 at gmail.com>
> Cc: stable at vger.kernel.org
> Cc: Takashi Iwai <tiwai at suse.de>
> Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> Cc: Todd Previte <tprevite at gmail.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

The commit was the fix for the memory corruption and lock up at S4 on
some (Haswell) machines.  This revert will re-introduce the issue
again very likely.  I'm going to check with the latest tree, but this
may take some time.

Wouldn't it be safer to revert this conditionally like I suggested in
comment 10 of the bugzilla entry?

--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -818,7 +818,7 @@ void i915_gem_suspend_gtt_mappings(struct
drm_device *dev)
        /* Don't bother messing with faults pre GEN6 as we have little
         * documentation supporting that it's a good idea.
         */
-       if (INTEL_INFO(dev)->gen < 6)
+       if (INTEL_INFO(dev)->gen < 7)
                return;
 
        i915_check_and_clear_faults(dev);

thanks,

Takashi


> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 5d61de18ae55..4467974eb53b 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -1281,7 +1281,7 @@ void i915_gem_suspend_gtt_mappings(struct drm_device *dev)
>  	dev_priv->gtt.base.clear_range(&dev_priv->gtt.base,
>  				       dev_priv->gtt.base.start,
>  				       dev_priv->gtt.base.total,
> -				       false);
> +				       true);
>  }
>  
>  void i915_gem_restore_gtt_mappings(struct drm_device *dev)
> -- 
> 1.8.5.2
>