Re: [PATCH] drm/i915: unconditionally use mt forcewake on hsw/ivb

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 18 Oct 2012 14:44:35 +0200
Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> Single-threaded forcewake was only used on some early pre-production
> ivybridge machines, all the latest ones should use mt forcewake. And
> we already assume this in other places of the code (e.g. DERRMR
> support in the ddx, or the latest intel_gt_reset patch to reset any
> lingering forcewake references left behind by the bios), so don't
> bother here, too.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/intel_pm.c |   31 ++++---------------------------
>  1 file changed, 4 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 2b3cddf..568c98d 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4146,35 +4146,12 @@ 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 (INTEL_INFO(dev)->gen >= 6) {
> +	} else if (IS_IVYBRIDGE(dev) || 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_GEN6(dev)) {
>  		dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
>  		dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;
> -
> -		/* IVB configs may use multi-threaded forcewake */
> -		if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
> -			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;
> -			}
> -		}
>  	}
>  }
>  

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Pretty sure it was just early, pre-production IVB that didn't use MT,
so this should be safe.

-- 
Jesse Barnes, Intel Open Source Technology Center