[Intel-gfx] [PATCH] drm/i915: Re-enable mt forcewake check for IVB

[Daniel Vetter]

On Thu, Nov 15, 2012 at 6:03 PM, Takashi Iwai <tiwai at suse.de> wrote:
> Some IVB machines seem to need non-MT forcewake.  Using MT forcewake
> on such machines result in broken or blank screens.
>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
> The commit 36ec8f877481449bdfa072e6adf2060869e2b970 triggered a
> regression on my test IVY laptops.  Instead of reverting the commit,
> I cooked a bit to make fitting only for IS_IVYBRIDGE().

Hm, that's rather bad since proper usage of DERRMR requires that we
enable rc6 on ivb, which is only really possible when we have
multi-threaded forcewake. Now I've thought that all production
machines have that enabled (it's something the bios should do), so the
big question: Is this a pre-production hw? If so, a bios upgrade
should fix it since historically we've killed pre-production
workarounds once the real hw ships, there are simply too many ...
-Daniel


>
>  drivers/gpu/drm/i915/intel_pm.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 0cbc0e6..944911e 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4239,9 +4239,36 @@ void intel_gt_init(struct drm_device *dev)
>         if (IS_VALLEYVIEW(dev)) {
>                 dev_priv->gt.force_wake_get = vlv_force_wake_get;
>                 dev_priv->gt.force_wake_put = vlv_force_wake_put;
> -       } else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
> +       } else if (IS_HASWELL(dev)) {
>                 dev_priv->gt.force_wake_get = __gen6_gt_force_wake_mt_get;
>                 dev_priv->gt.force_wake_put = __gen6_gt_force_wake_mt_put;
> +       } else if (IS_IVYBRIDGE(dev)) {
> +               /* IVB configs may use multi-threaded forcewake */
> +               u32 ecobus;
> +
> +               /* A small trick here - if the bios hasn't configured
> +                * MT forcewake, and if the device is in RC6, then
> +                * force_wake_mt_get will not wake the device and the
> +                * ECOBUS read will return zero. Which will be
> +                * (correctly) interpreted by the test below as MT
> +                * forcewake being disabled.
> +                */
> +               mutex_lock(&dev->struct_mutex);
> +               __gen6_gt_force_wake_mt_get(dev_priv);
> +               ecobus = I915_READ_NOTRACE(ECOBUS);
> +               __gen6_gt_force_wake_mt_put(dev_priv);
> +               mutex_unlock(&dev->struct_mutex);
> +
> +               if (ecobus & FORCEWAKE_MT_ENABLE) {
> +                       DRM_DEBUG_KMS("Using MT version of forcewake\n");
> +                       dev_priv->gt.force_wake_get =
> +                               __gen6_gt_force_wake_mt_get;
> +                       dev_priv->gt.force_wake_put =
> +                               __gen6_gt_force_wake_mt_put;
> +               } else {
> +                       dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
> +                       dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;
> +               }
>         } else if (IS_GEN6(dev)) {
>                 dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
>                 dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;
> --
> 1.8.0
>



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch