Re: [PATCH 6/6] drm/i915/gen10: Calculate and enable transition WM

["Lankhorst, Maarten" <maarten.lankhorst@intel.com>]

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Hey,

Mahesh Kumar schreef op di 13-06-2017 om 11:34 [+0530]:
> GEN > 9 require transition WM to be programmed if IPC is enabled.
> This patch calculates & enable transition WM for supported platforms.
> If transition WM is enabled, Plane read requests are sent at high
> priority until filling above the transition watermark, then the
> requests are sent at lower priority until dropping below the level-0
> WM.
> The lower priority requests allow other memory clients to have better
> memory access.
> 
> transition minimum is the minimum amount needed for trans_wm to work
> to
> ensure  the demote does not happen before enough data has been read
> to
> meet the level 0 watermark requirements.
> 
> transition amount is configurable value. Higher values will
> tend to cause longer periods of high priority reads followed by
> longer
> periods of lower priority reads. Tuning to lower values will tend to
> cause shorter periods of high and lower priority reads.
> 
> Keeping transition amount to 0 in this patch.

> Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 51
> ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 48 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> index 10ec2660acd7..6b951aa14840 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4163,6 +4163,15 @@ skl_enable_plane_wm_levels(const struct
> drm_i915_private *dev_priv,
>  			level_wm->plane_en = true;
>  		}
>  	}
> +
> +	/*
> +	 * Unsupported GEN will have plane_res_b = 0 & transition WM
> for
> +	 * them will get disabled here.
> +	 */
> +	if (wm->trans_wm.plane_res_b && wm->trans_wm.plane_res_b <
> plane_ddb)
> +		wm->trans_wm.plane_en = true;
> +	else
> +		wm->trans_wm.plane_en = false;
>  }
>  
>  static int
> @@ -4639,13 +4648,48 @@ skl_compute_linetime_wm(struct
> intel_crtc_state *cstate)
>  }
>  
>  static void skl_compute_transition_wm(struct intel_crtc_state
> *cstate,
> +				      struct skl_wm_params *wp,
> +				      struct skl_wm_level *wm_l0,
>  				      struct skl_wm_level *trans_wm
> /* out */)
>  {
> +	struct drm_device *dev = cstate->base.crtc->dev;
> +	const struct drm_i915_private *dev_priv = to_i915(dev);
> +	uint16_t trans_min, trans_y_tile_min;
> +	uint16_t trans_amount = 0; /* This is configurable amount */
> +	uint16_t trans_offset_b, res_blocks;
> +
>  	if (!cstate->base.active)
>  		return;
> -	/* Until we know more, just disable transition WMs */
> -	trans_wm->plane_en = false;
> +	/* Transition WM are not recommended by HW team for GEN9 */
> +	if (INTEL_GEN(dev_priv) <= 9)
> +		return;
> +
> +	/* Transition WM don't have any impact if ipc is disabled */
> +	if (!dev_priv->ipc_enabled)
> +		return;
ipc_enabled is never set, so this patch on its own doesn't do much. :)

Otherwise series looks good, I didn't check the math on this patch,
but the series doesn't regress KBL.

For patch 3 and 4:
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

For patch 5 and 6:
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

> +	if (INTEL_GEN(dev_priv) >= 10)
> +		trans_min = 4;
> +
> +	trans_offset_b = trans_min + trans_amount;
> +	trans_y_tile_min = (uint16_t) mul_round_up_u32_fixed16(2,
> +							wp-
> >y_tile_minimum);
> +
> +	if (wp->y_tiled) {
> +		res_blocks = max(wm_l0->plane_res_b,
> trans_y_tile_min) +
> +				trans_offset_b;
> +	} else {
> +		res_blocks = wm_l0->plane_res_b + trans_offset_b;
> +	}
> +
> +	res_blocks += 1;
> +
> +	/* WA BUG:1938466 add one block for non y-tile planes */
> +	if (!wp->y_tiled && IS_CNL_REVID(dev_priv, CNL_REVID_A0,
> CNL_REVID_A0))
> +		res_blocks += 1;
> +
> +	trans_wm->plane_res_b = res_blocks;
>  }
>  
>  static int skl_build_pipe_wm(struct intel_crtc_state *cstate,
> @@ -4684,7 +4728,8 @@ static int skl_build_pipe_wm(struct
> intel_crtc_state *cstate,
>  					    &wm_params, wm);
>  		if (ret)
>  			return ret;
> -		skl_compute_transition_wm(cstate, &wm->trans_wm);
> +		skl_compute_transition_wm(cstate, &wm_params, &wm-
> >wm[0],
> +					  &wm->trans_wm);
>  	}
>  	pipe_wm->linetime = skl_compute_linetime_wm(cstate);
>  

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