Re: [PATCH v6 8/8] drm/i915/gen9: WM memory bandwidth related workaround

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Mahesh Kumar schreef op do 24-11-2016 om 09:31 [+0530]:
> This patch implemnets Workariunds related to display arbitrated
> memory
> bandwidth. These WA are applicabe for all gen-9 based platforms.
> 
> Changes since v1:
>  - Rebase on top of Paulo's patch series
> Changes since v2:
>  - Address review comments
>  - Rebase/rework as per other patch changes in series
> 
> Signed-off-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/i915_drv.h |   9 +++
>  drivers/gpu/drm/i915/intel_pm.c | 149
> +++++++++++++++++++++++++++++++++++++---
>  2 files changed, 149 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> b/drivers/gpu/drm/i915/i915_drv.h
> index 4e2f17f..2b673c6 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1193,6 +1193,13 @@ enum intel_sbi_destination {
>  	SBI_MPHY,
>  };
>  
> +/* SKL+ Watermark arbitrated display bandwidth Workarounds */
> +enum watermark_memory_wa {
> +	WATERMARK_WA_NONE,
> +	WATERMARK_WA_X_TILED,
> +	WATERMARK_WA_Y_TILED,
> +};
> +
>  #define QUIRK_PIPEA_FORCE (1<<0)
>  #define QUIRK_LVDS_SSC_DISABLE (1<<1)
>  #define QUIRK_INVERT_BRIGHTNESS (1<<2)
> @@ -1764,6 +1771,8 @@ struct skl_ddb_allocation {
>  
>  struct skl_wm_values {
>  	unsigned dirty_pipes;
> +	/* any WaterMark memory workaround Required */
> +	enum watermark_memory_wa mem_wa;
>  	struct skl_ddb_allocation ddb;
>  };
>  
> diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> index 3e2dd8f..547bbda 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2889,11 +2889,7 @@ skl_wm_plane_id(const struct intel_plane
> *plane)
>  	}
>  }
>  
> -/*
> - * FIXME: We still don't have the proper code detect if we need to
> apply the WA,
> - * so assume we'll always need it in order to avoid underruns.
> - */
> -static bool skl_needs_memory_bw_wa(struct intel_atomic_state *state)
> +static bool intel_needs_memory_bw_wa(struct intel_atomic_state
> *state)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(state-
> >base.dev);
>  
> @@ -3067,7 +3063,7 @@ bool intel_can_enable_sagv(struct
> drm_atomic_state *state)
>  
>  		latency = dev_priv->wm.skl_latency[level];
>  
> -		if (skl_needs_memory_bw_wa(intel_state) &&
> +		if (intel_needs_memory_bw_wa(intel_state) &&
>  		    plane->base.state->fb->modifier ==
>  		    I915_FORMAT_MOD_X_TILED)
>  			latency += 15;
> @@ -3597,7 +3593,7 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  	uint32_t y_min_scanlines;
>  	struct intel_atomic_state *state =
>  		to_intel_atomic_state(cstate->base.state);
> -	bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
> +	enum watermark_memory_wa mem_wa;
>  	bool y_tiled, x_tiled;
>  
>  	if (latency == 0 || !cstate->base.active || !intel_pstate-
> >base.visible) {
> @@ -3613,7 +3609,8 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  	if (IS_KABYLAKE(dev_priv) && dev_priv->ipc_enabled)
>  		latency += 4;
>  
> -	if (apply_memory_bw_wa && x_tiled)
> +	mem_wa = state->wm_results.mem_wa;
> +	if (mem_wa != WATERMARK_WA_NONE && x_tiled)
>  		latency += 15;
>  
>  	width = drm_rect_width(&intel_pstate->base.src) >> 16;
> @@ -3648,7 +3645,7 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  		y_min_scanlines = 4;
>  	}
>  
> -	if (apply_memory_bw_wa)
> +	if (mem_wa == WATERMARK_WA_Y_TILED)
>  		y_min_scanlines *= 2;
>  
>  	plane_bytes_per_line = width * cpp;
> @@ -4077,6 +4074,15 @@ skl_compute_ddb(struct drm_atomic_state
> *state)
>  	}
>  
>  	/*
> +	 * If Watermark workaround is changed we need to recalculate
> +	 * watermark values for all active pipes
> +	 */
> +	if (intel_state->wm_results.mem_wa != dev_priv-
> >wm.skl_hw.mem_wa) {
> +		realloc_pipes = ~0;
> +		intel_state->wm_results.dirty_pipes = ~0;
> +	}
> +
> +	/*
>  	 * We're not recomputing for the pipes not included in the
> commit, so
>  	 * make sure we start with the current state.
>  	 */
> @@ -4102,6 +4108,129 @@ skl_compute_ddb(struct drm_atomic_state
> *state)
>  }
>  
>  static void
> +skl_compute_memory_bandwidth_wm_wa(struct drm_atomic_state *state)
> +{
> +	struct drm_device *dev = state->dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct intel_crtc *intel_crtc;
> +	struct intel_plane_state *intel_pstate;
> +	struct intel_atomic_state *intel_state =
> to_intel_atomic_state(state);
> +	struct memdev_info *memdev_info = &dev_priv->memdev_info;
> +	int num_active_pipes;
> +	uint32_t max_pipe_bw_kbps, total_pipe_bw_kbps;
> +	int display_bw_percentage;
> +	bool y_tile_enabled = false;
> +
> +	if (!intel_needs_memory_bw_wa(intel_state)) {
> +		intel_state->wm_results.mem_wa = WATERMARK_WA_NONE;
> +		return;
> +	}
> +
> +	if (!memdev_info->valid)
> +		goto exit;
> +
> +	max_pipe_bw_kbps = 0;
> +	num_active_pipes = 0;
> +	for_each_intel_crtc(dev, intel_crtc) {
> +		struct intel_crtc_state *cstate;
> +		struct intel_plane *plane;
> +		int num_active_planes;
> +		uint32_t  max_plane_bw_kbps, pipe_bw_kbps;
> +
> +		/*
> +		 * If CRTC is part of current atomic commit, get
> crtc state from
> +		 * existing CRTC state. else take the cached CRTC
> state
> +		 */
> +		cstate = NULL;
> +		if (state)
> +			cstate =
> intel_atomic_get_existing_crtc_state(state,
> +					intel_crtc);
> +		if (!cstate)
> +			cstate = to_intel_crtc_state(intel_crtc-
> >base.state);
This is really really not allowed. If you want to access
crtc->state, you need to get the state.

Since a w/a forces a full recalculation, best you can do is put the per
pipe status in crtc_state->wm.skl as well. If it changes you could add
all other pipes.

> +		if (!cstate->base.active)
> +			continue;
> +
> +		num_active_planes = 0;
> +		max_plane_bw_kbps = 0;
> +		for_each_intel_plane_mask(dev, plane, cstate-
> >base.plane_mask) {
This is very much not allowed either!

If you want to do this safely and you hold crtc_state, use
drm_atomic_crtc_state_for_each_plane_state.
> +			struct drm_framebuffer *fb;
> +			uint32_t plane_bw_kbps;
> +			uint32_t id = skl_wm_plane_id(plane);
> +
> +			intel_pstate = NULL;
> +			intel_pstate =
> +				intel_atomic_get_existing_plane_stat
> e(state,
> +									
> plane);
> +			if (!intel_pstate)
> +				intel_pstate =
> +					to_intel_plane_state(plane-
> >base.state);
> +
> +			if (!intel_pstate->base.visible)
> +				continue;
> +
> +			if (WARN_ON(!intel_pstate->base.fb))
> +				continue;
> +
> +			if (id == PLANE_CURSOR)
> +				continue;
> +
> +			fb = intel_pstate->base.fb;
> +			if ((fb->modifier == I915_FORMAT_MOD_Y_TILED
> ||
> +				fb->modifier ==
> I915_FORMAT_MOD_Yf_TILED))
> +				y_tile_enabled = true;
> +
> +			plane_bw_kbps =
> skl_adjusted_plane_pixel_rate(cstate,
> +								inte
> l_pstate);
> +			max_plane_bw_kbps = max(plane_bw_kbps,
> +							max_plane_bw
> _kbps);
> +			num_active_planes++;
> +		}
> +		pipe_bw_kbps = max_plane_bw_kbps *
> num_active_planes;
> +		max_pipe_bw_kbps = max(pipe_bw_kbps,
> max_pipe_bw_kbps);
> +		num_active_pipes++;
> +	}
> +
> +	total_pipe_bw_kbps = max_pipe_bw_kbps * num_active_pipes;
> +
> +	display_bw_percentage = DIV_ROUND_UP_ULL(total_pipe_bw_kbps
> * 100,
> +						memdev_info-
> >bandwidth_kbps);
> +
> +	/*
> +	 * If there is any Ytile plane enabled and arbitrated
> display
> +	 * bandwidth > 20% of raw system memory bandwidth
> +	 * Enale Y-tile related WA
> +	 *
> +	 * If memory is dual channel single rank, Xtile limit = 35%,
> else Xtile
> +	 * limit = 60%
> +	 * If there is no Ytile plane enabled and
> +	 * arbitrated display bandwidth > Xtile limit
> +	 * Enable X-tile realated WA
> +	 */
> +	if (y_tile_enabled && (display_bw_percentage > 20))
> +		intel_state->wm_results.mem_wa =
> WATERMARK_WA_Y_TILED;
> +	else {
> +		int x_tile_percentage = 60;
> +		enum rank rank = DRAM_RANK_SINGLE;
> +
> +		if (memdev_info->rank != DRAM_RANK_INVALID)
> +			rank = memdev_info->rank;
> +
> +		if ((rank == DRAM_RANK_SINGLE) &&
> +					(memdev_info->num_channels
> == 2))
> +			x_tile_percentage = 35;
> +
> +		if (display_bw_percentage > x_tile_percentage)
> +			intel_state->wm_results.mem_wa =
> WATERMARK_WA_X_TILED;
> +	}
> +	return;
> +
> +exit:
> +	intel_state->wm_results.mem_wa = WATERMARK_WA_Y_TILED;
> +}
> +
> +
> +static void
>  skl_copy_wm_for_pipe(struct skl_wm_values *dst,
>  		     struct skl_wm_values *src,
>  		     enum pipe pipe)
> @@ -4177,6 +4306,8 @@ skl_compute_wm(struct drm_atomic_state *state)
>  	/* Clear all dirty flags */
>  	results->dirty_pipes = 0;
>  
> +	skl_compute_memory_bandwidth_wm_wa(state);
> +
>  	ret = skl_compute_ddb(state);
>  	if (ret)
>  		return ret;
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