[Intel-gfx] [PATCH 11/13] drm/i915: Turn off pipe gamma when it's not needed.

[Matt Roper]

On Fri, Jan 11, 2019 at 07:08:21PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The pipe internal precision is higher than what we currently program to
> the degamma/gamma LUTs. We can get a higher quality image by bypassing
> the LUTs when they're not needed. Let's do that.
> 
> Each plane has its own control bit for this, so we have to update
> all active planes. The way we've done this we don't actually have
> to run through the whole .check_plane() thing. And we actually
> do the .color_check() after .check_plane() so we couldn't even do
> that without shuffling the code around.
> 
> Additionally on pre-skl we have to update the primary plane regardless
> of whether it's active or not on account of the primayr plane gamma

s/primayr/primary/

> enable bit also affecting the pipe bottom color.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_color.c | 55 ++++++++++++++++++++++++++++--
>  1 file changed, 53 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_color.c b/drivers/gpu/drm/i915/intel_color.c
> index 8d7ea902a34b..a8b7428a64bf 100644
> --- a/drivers/gpu/drm/i915/intel_color.c
> +++ b/drivers/gpu/drm/i915/intel_color.c
> @@ -633,27 +633,78 @@ void intel_color_commit(const struct intel_crtc_state *crtc_state)
>  	dev_priv->display.color_commit(crtc_state);
>  }
>  
> +static bool need_plane_update(struct intel_plane *plane,
> +			      const struct intel_crtc_state *crtc_state)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
> +
> +	/*
> +	 * On pre-SKL the pipe gamma enable and pipe csc enable for
> +	 * the pipe bottom color are configured via the primary plane.
> +	 * We have to reconfigure that even if the plane is inactive.
> +	 */
> +	return crtc_state->active_planes & BIT(plane->id) ||
> +		(INTEL_GEN(dev_priv) < 9 &&
> +		 plane->id == PLANE_PRIMARY);
> +}
> +
> +static int
> +intel_color_add_affected_planes(struct intel_crtc_state *new_crtc_state)
> +{
> +	struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->base.crtc);
> +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> +	struct intel_atomic_state *state =
> +		to_intel_atomic_state(new_crtc_state->base.state);
> +	const struct intel_crtc_state *old_crtc_state =
> +		intel_atomic_get_old_crtc_state(state, crtc);
> +	struct intel_plane *plane;
> +
> +	if (new_crtc_state->gamma_enable == old_crtc_state->gamma_enable)
> +		return 0;
> +
> +	for_each_intel_plane_on_crtc(&dev_priv->drm, crtc, plane) {
> +		struct intel_plane_state *plane_state;
> +
> +		if (!need_plane_update(plane, new_crtc_state))
> +			continue;
> +
> +		plane_state = intel_atomic_get_plane_state(state, plane);
> +		if (IS_ERR(plane_state))
> +			return PTR_ERR(plane_state);
> +
> +		new_crtc_state->update_planes |= BIT(plane->id);
> +	}
> +
> +	return 0;
> +}
> +
>  int intel_color_check(struct intel_crtc_state *crtc_state)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
>  	const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
>  	const struct drm_property_blob *degamma_lut = crtc_state->base.degamma_lut;
>  	size_t gamma_length, degamma_length;
> +	int ret;
>  
>  	degamma_length = INTEL_INFO(dev_priv)->color.degamma_lut_size;
>  	gamma_length = INTEL_INFO(dev_priv)->color.gamma_lut_size;
>  
> -	crtc_state->gamma_enable = true;
> +	crtc_state->gamma_enable = gamma_lut || degamma_lut;
>  
>  	if (INTEL_GEN(dev_priv) >= 9 ||
>  	    IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
>  		crtc_state->csc_enable = true;
>  
> +	ret = intel_color_add_affected_planes(crtc_state);
> +	if (ret)
> +		return ret;
> +
>  	/*
>  	 * We also allow no degamma lut/ctm and a gamma lut at the legacy
>  	 * size (256 entries).
>  	 */
> -	if (crtc_state_is_legacy_gamma(crtc_state)) {
> +	if (!crtc_state->gamma_enable ||
> +	    crtc_state_is_legacy_gamma(crtc_state)) {
>  		crtc_state->gamma_mode = GAMMA_MODE_MODE_8BIT;

If none of our planes are actually using the gamma, what does switching
back to 8bit mode do for us?

Regardless,

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>


>  		return 0;
>  	}
> -- 
> 2.19.2
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795