Re: [Intel-gfx] [PATCH 3/3] drm/i915: Workaround broken BIOS DBUF configuration on TGL/RKL

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Fri, Feb 04, 2022 at 04:18:18PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> On TGL/RKL the BIOS likes to use some kind of bogus DBUF layout
> that doesn't match what the spec recommends. With a single active
> pipe that is not going to be a problem, but with multiple pipes
> active skl_commit_modeset_enables() goes into an infinite loop
> since it can't figure out any order in which it can commit the
> pipes without causing DBUF overlaps between the planes.
> 
> We'd need some kind of extra DBUF defrag stage in between to
> make the transition possible. But that is clearly way too complex
> a solution, so in the name of simplicity let's just sanitize the
> DBUF state by simply turning off all planes when we detect a
> pipe encroaching on its neighbours' DBUF slices. We only have
> to disable the primary planes as all other planes should have
> already been disabled (if they somehow were enabled) by
> earlier sanitization steps.
> 
> And for good measure let's also sanitize in case the DBUF
> allocations of the pipes already seem to overlap each other.
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4762
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_display.c |  1 +
>  drivers/gpu/drm/i915/intel_pm.c              | 68 ++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_pm.h              |  1 +
>  3 files changed, 70 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index df347329d90e..7f512f9e9e5c 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -10649,6 +10649,7 @@ intel_modeset_setup_hw_state(struct drm_device *dev,
>  		vlv_wm_sanitize(dev_priv);
>  	} else if (DISPLAY_VER(dev_priv) >= 9) {
>  		skl_wm_get_hw_state(dev_priv);
> +		skl_wm_sanitize(dev_priv);
>  	} else if (HAS_PCH_SPLIT(dev_priv)) {
>  		ilk_wm_get_hw_state(dev_priv);
>  	}
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 79d61a2935ea..02084652fe3d 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -6710,6 +6710,74 @@ void skl_wm_get_hw_state(struct drm_i915_private *dev_priv)
>  	dbuf_state->enabled_slices = dev_priv->dbuf.enabled_slices;
>  }
>  
> +static bool skl_dbuf_is_misconfigured(struct drm_i915_private *i915)
> +{
> +	const struct intel_dbuf_state *dbuf_state =
> +		to_intel_dbuf_state(i915->dbuf.obj.state);
> +	struct skl_ddb_entry entries[I915_MAX_PIPES] = {};
> +	struct intel_crtc *crtc;
> +
> +	for_each_intel_crtc(&i915->drm, crtc) {
> +		const struct intel_crtc_state *crtc_state =
> +			to_intel_crtc_state(crtc->base.state);
> +
> +		entries[crtc->pipe] = crtc_state->wm.skl.ddb;
> +	}
> +
> +	for_each_intel_crtc(&i915->drm, crtc) {
> +		const struct intel_crtc_state *crtc_state =
> +			to_intel_crtc_state(crtc->base.state);
> +		u8 slices;
> +
> +		slices = skl_compute_dbuf_slices(crtc, dbuf_state->active_pipes,
> +						 dbuf_state->joined_mbus);
> +		if (dbuf_state->slices[crtc->pipe] & ~slices)
> +			return true;
> +
> +		if (skl_ddb_allocation_overlaps(&crtc_state->wm.skl.ddb, entries,
> +						I915_MAX_PIPES, crtc->pipe))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +void skl_wm_sanitize(struct drm_i915_private *i915)
> +{
> +	struct intel_crtc *crtc;
> +
> +	/*
> +	 * On TGL/RKL (at least) the BIOS likes to assign the planes
> +	 * to the wrong DBUF slices. This will cause an infinite loop
> +	 * in skl_commit_modeset_enables() as it can't find a way to
> +	 * transition between the old bogus DBUF layout to the new
> +	 * proper DBUF layout without DBUF allocation overlaps between
> +	 * the planes (which cannot be allowed or else the hardware
> +	 * may hang). If we detect a bogus DBUF layout just turn off
> +	 * all the planes so that skl_commit_modeset_enables() can
> +	 * simply ignore them.
> +	 */
> +	if (!skl_dbuf_is_misconfigured(i915))
> +		return;
> +
> +	drm_dbg_kms(&i915->drm, "BIOS has misprogrammed the DBUF, disabling all planes\n");
> +
> +	for_each_intel_crtc(&i915->drm, crtc) {
> +		struct intel_plane *plane = to_intel_plane(crtc->base.primary);
> +		const struct intel_plane_state *plane_state =
> +			to_intel_plane_state(plane->base.state);
> +		struct intel_crtc_state *crtc_state =
> +			to_intel_crtc_state(crtc->base.state);
> +
> +		if (plane_state->uapi.visible)
> +			intel_plane_disable_noatomic(crtc, plane);
> +
> +		drm_WARN_ON(&i915->drm, crtc_state->active_planes != 0);
> +
> +		memset(&crtc_state->wm.skl.ddb, 0, sizeof(crtc_state->wm.skl.ddb));
> +	}
> +}
> +
>  static void ilk_pipe_wm_get_hw_state(struct intel_crtc *crtc)
>  {
>  	struct drm_device *dev = crtc->base.dev;
> diff --git a/drivers/gpu/drm/i915/intel_pm.h b/drivers/gpu/drm/i915/intel_pm.h
> index ae821e35d5fc..51705151b842 100644
> --- a/drivers/gpu/drm/i915/intel_pm.h
> +++ b/drivers/gpu/drm/i915/intel_pm.h
> @@ -46,6 +46,7 @@ void skl_pipe_wm_get_hw_state(struct intel_crtc *crtc,
>  			      struct skl_pipe_wm *out);
>  void g4x_wm_sanitize(struct drm_i915_private *dev_priv);
>  void vlv_wm_sanitize(struct drm_i915_private *dev_priv);
> +void skl_wm_sanitize(struct drm_i915_private *dev_priv);
>  bool intel_can_enable_sagv(struct drm_i915_private *dev_priv,
>  			   const struct intel_bw_state *bw_state);
>  void intel_sagv_pre_plane_update(struct intel_atomic_state *state);
> -- 
> 2.34.1
>