Re: [PATCH 1/2] drm/i915/icl: Drop spurious register read from icl_dbuf_slices_update

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

On Fri, Nov 09, 2018 at 04:09:23PM +0200, Mika Kuoppala wrote:
> Register DBUF_CTL_S2 is read and it's value is not used. As
> there is no explanation why we should prime the hardware with
> read, remove it as spurious.
> 
> Fixes: aa9664ffe863 ("drm/i915/icl: Enable 2nd DBuf slice only when needed")
> Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index f945db6ea420..770de2632530 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -3236,8 +3236,7 @@ static u8 intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
>  void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
>  			    u8 req_slices)
>  {
> -	u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
> -	u32 val;
> +	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
>  	bool ret;
>  
>  	if (req_slices > intel_dbuf_max_slices(dev_priv)) {
> @@ -3248,7 +3247,6 @@ void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
>  	if (req_slices == hw_enabled_slices || req_slices == 0)
>  		return;
>  
> -	val = I915_READ(DBUF_CTL_S2);
>  	if (req_slices > hw_enabled_slices)
>  		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, true);
>  	else
> -- 
> 2.17.1
> 
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