Re: [PATCH] drm/i915/icl: Prevent incorrect DBuf enabling

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Mar 07, 2019 at 12:32:35PM +0200, Imre Deak wrote:
> Pretend that we have only 1 DBuf slice and that 1 slice is always
> enabled, until we have a proper way for on-demand toggling of the second
> slice.  Currently we'll try to incorrectly enable DBuf even when all
> pipes are disabled and we are already runtime suspended (as the computed
> number of DBuf slices will be 1 in that case).
> 
> This also means we'll leave the second slice enabled redundantly (except
> when suspended), but that's an acceptable tradeoff until we have a
> proper solution.

redundant is the word of the week :)

> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108756
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c         |  7 ++++++-
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 12 ++++++++++--
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 9c97a95c1816..bece16ae6d15 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3624,7 +3624,12 @@ static u8 intel_enabled_dbuf_slices_num(struct drm_i915_private *dev_priv)
>  	if (INTEL_GEN(dev_priv) < 11)
>  		return enabled_slices;
>  
> -	if (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
> +	/*
> +	 * FIXME: for now we'll only ever use 1 slice; pretend that we have
> +	 * only that 1 slice enabled until we have a proper way for on-demand
> +	 * toggling of the second slice.
> +	 */
> +	if (0 && I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)

what if just add a check for enabled_slices >= 2 and avoid the FIXME here?

but up to you:

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

>  		enabled_slices++;
>  
>  	return enabled_slices;
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index aa974b11928a..676a89bb8194 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -3576,7 +3576,11 @@ static void icl_dbuf_enable(struct drm_i915_private *dev_priv)
>  	    !(I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
>  		DRM_ERROR("DBuf power enable timeout\n");
>  	else
> -		dev_priv->wm.skl_hw.ddb.enabled_slices = 2;
> +		/*
> +		 * FIXME: for now pretend that we only have 1 slice, see
> +		 * intel_enabled_dbuf_slices_num().
> +		 */
> +		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
>  }
>  
>  static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
> @@ -3591,7 +3595,11 @@ static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
>  	    (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
>  		DRM_ERROR("DBuf power disable timeout!\n");
>  	else
> -		dev_priv->wm.skl_hw.ddb.enabled_slices = 0;
> +		/*
> +		 * FIXME: for now pretend that the first slice is always
> +		 * enabled, see intel_enabled_dbuf_slices_num().
> +		 */
> +		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
>  }
>  
>  static void icl_mbus_init(struct drm_i915_private *dev_priv)
> -- 
> 2.13.2
> 
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