Re: [Intel-gfx] [PATCH 01/20] drm/i915/fbc: Eliminate racy intel_fbc_is_active() usage

["Kahola, Mika" <mika.kahola@intel.com>]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, November 24, 2021 1:37 PM
> To: intel-gfx@lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 01/20] drm/i915/fbc: Eliminate racy
> intel_fbc_is_active() usage
> 
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The ilk fbc watermark computation uses intel_fbc_is_active() which is racy since
> we don't know whether FBC will be enabled or not at some point. So let's just
> assume it will be if both HAS_FBC() and the modparam agree.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Mika Kahola <mika.kahola@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 01fa3fac1b57..18fbdd204a93 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3369,13 +3369,8 @@ static void ilk_wm_merge(struct drm_i915_private
> *dev_priv,
>  	}
> 
>  	/* ILK: LP2+ must be disabled when FBC WM is disabled but FBC enabled
> */
> -	/*
> -	 * FIXME this is racy. FBC might get enabled later.
> -	 * What we should check here is whether FBC can be
> -	 * enabled sometime later.
> -	 */
> -	if (DISPLAY_VER(dev_priv) == 5 && !merged->fbc_wm_enabled &&
> -	    intel_fbc_is_active(&dev_priv->fbc)) {
> +	if (DISPLAY_VER(dev_priv) == 5 && HAS_FBC(dev_priv) &&
> +	    dev_priv->params.enable_fbc && !merged->fbc_wm_enabled) {
>  		for (level = 2; level <= max_level; level++) {
>  			struct intel_wm_level *wm = &merged->wm[level];
> 
> --
> 2.32.0