Re: [PATCH v4 2/2] drm/i915: Restrict qgv points which don't have enough bandwidth.

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On Tue, Oct 15, 2019 at 04:50:13PM +0300, Stanislav Lisovskiy wrote:
> According to BSpec 53998, we should try to
> restrict qgv points, which can't provide
> enough bandwidth for desired display configuration.
> 
> Currently we are just comparing against all of
> those and take minimum(worst case).
> 
> v2: Fixed wrong PCode reply mask, removed hardcoded
>     values.
> 
> v3: Forbid simultaneous legacy SAGV PCode requests and
>     restricting qgv points. Put the actual restriction
>     to commit function, added serialization(thanks to Ville)
>     to prevent commit being applied out of order in case of
>     nonblocking and/or nomodeset commits.
> 
> v4:
>     - Minor code refactoring, fixed few typos(thanks to James Ausmus)
>     - Change the naming of qgv point
>       masking/unmasking functions(James Ausmus).
>     - Simplify the masking/unmasking operation itself,
>       as we don't need to mask only single point per request(James Ausmus)
>     - Reject and stick to highest bandwidth point if SAGV
>       can't be enabled(BSpec)
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxx>
> Cc: James Ausmus <james.ausmus@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/display/intel_atomic.c   |  16 +++
>  drivers/gpu/drm/i915/display/intel_atomic.h   |   3 +
>  drivers/gpu/drm/i915/display/intel_bw.c       | 105 ++++++++++++++----
>  drivers/gpu/drm/i915/display/intel_bw.h       |   2 +
>  drivers/gpu/drm/i915/display/intel_display.c  |  58 +++++++++-
>  .../drm/i915/display/intel_display_types.h    |   3 +
>  drivers/gpu/drm/i915/i915_drv.h               |   2 +
>  drivers/gpu/drm/i915/i915_reg.h               |   3 +
>  8 files changed, 166 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
> index c5a552a69752..b3f4f02f380b 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic.c
> @@ -207,6 +207,22 @@ intel_crtc_duplicate_state(struct drm_crtc *crtc)
>  	return &crtc_state->base;
>  }
>  
> +int intel_atomic_serialize_global_state(struct intel_atomic_state *state)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> +	struct intel_crtc *crtc;
> +
> +	for_each_intel_crtc(&dev_priv->drm, crtc) {
> +		struct intel_crtc_state *crtc_state;
> +
> +		crtc_state = intel_atomic_get_crtc_state(&state->base, crtc);
> +		if (IS_ERR(crtc_state))
> +			return PTR_ERR(crtc_state);
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * intel_crtc_destroy_state - destroy crtc state
>   * @crtc: drm crtc
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.h b/drivers/gpu/drm/i915/display/intel_atomic.h
> index 58065d3161a3..fd17b3ca257f 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic.h
> +++ b/drivers/gpu/drm/i915/display/intel_atomic.h
> @@ -7,6 +7,7 @@
>  #define __INTEL_ATOMIC_H__
>  
>  #include <linux/types.h>
> +#include "intel_display_types.h"
>  
>  struct drm_atomic_state;
>  struct drm_connector;
> @@ -38,6 +39,8 @@ void intel_crtc_destroy_state(struct drm_crtc *crtc,
>  struct drm_atomic_state *intel_atomic_state_alloc(struct drm_device *dev);
>  void intel_atomic_state_clear(struct drm_atomic_state *state);
>  
> +int intel_atomic_serialize_global_state(struct intel_atomic_state *state);
> +
>  struct intel_crtc_state *
>  intel_atomic_get_crtc_state(struct drm_atomic_state *state,
>  			    struct intel_crtc *crtc);
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> index 22e83f857de8..09f786cfdfaa 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -8,6 +8,8 @@
>  #include "intel_bw.h"
>  #include "intel_display_types.h"
>  #include "intel_sideband.h"
> +#include "intel_atomic.h"
> +#include "intel_pm.h"
>  
>  /* Parameters for Qclk Geyserville (QGV) */
>  struct intel_qgv_point {
> @@ -113,6 +115,27 @@ static int icl_pcode_read_qgv_point_info(struct drm_i915_private *dev_priv,
>  	return 0;
>  }
>  
> +int icl_pcode_restrict_qgv_points(struct drm_i915_private *dev_priv,
> +				  u32 points_mask)
> +{
> +	int ret;
> +
> +	/* bspec says to keep retrying for at least 1 ms */
> +	ret = skl_pcode_request(dev_priv, ICL_PCODE_SAGV_DE_MEM_SS_CONFIG,
> +				points_mask,
> +				GEN11_PCODE_POINTS_RESTRICTED_MASK,
> +				GEN11_PCODE_POINTS_RESTRICTED,
> +				1);
> +
> +	if (ret < 0) {
> +		DRM_ERROR("Failed to disable qgv points (%d)\n", ret);

This could also be enabling qgv points, so this might better be "Failed
to set qgv point mask".

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +
>  static int icl_get_qgv_points(struct drm_i915_private *dev_priv,
>  			      struct intel_qgv_info *qi)
>  {
> @@ -270,22 +293,6 @@ void intel_bw_init_hw(struct drm_i915_private *dev_priv)
>  		icl_get_bw_info(dev_priv, &icl_sa_info);
>  }
>  
> -static unsigned int intel_max_data_rate(struct drm_i915_private *dev_priv,
> -					int num_planes)
> -{
> -	if (INTEL_GEN(dev_priv) >= 11)
> -		/*
> -		 * FIXME with SAGV disabled maybe we can assume
> -		 * point 1 will always be used? Seems to match
> -		 * the behaviour observed in the wild.
> -		 */
> -		return min3(icl_max_bw(dev_priv, num_planes, 0),
> -			    icl_max_bw(dev_priv, num_planes, 1),
> -			    icl_max_bw(dev_priv, num_planes, 2));
> -	else
> -		return UINT_MAX;
> -}
> -
>  static unsigned int intel_bw_crtc_num_active_planes(const struct intel_crtc_state *crtc_state)
>  {
>  	/*
> @@ -377,7 +384,10 @@ int intel_bw_atomic_check(struct intel_atomic_state *state)
>  	unsigned int data_rate, max_data_rate;
>  	unsigned int num_active_planes;
>  	struct intel_crtc *crtc;
> -	int i;
> +	int i, ret;
> +	struct intel_qgv_info qi = {};
> +	u32 allowed_points = 0;
> +	unsigned int max_bw_point = 0, max_bw = 0;
>  
>  	/* FIXME earlier gens need some checks too */
>  	if (INTEL_GEN(dev_priv) < 11)
> @@ -421,16 +431,67 @@ int intel_bw_atomic_check(struct intel_atomic_state *state)
>  	data_rate = intel_bw_data_rate(dev_priv, bw_state);
>  	num_active_planes = intel_bw_num_active_planes(dev_priv, bw_state);
>  
> -	max_data_rate = intel_max_data_rate(dev_priv, num_active_planes);
> -
>  	data_rate = DIV_ROUND_UP(data_rate, 1000);
>  
> -	if (data_rate > max_data_rate) {
> -		DRM_DEBUG_KMS("Bandwidth %u MB/s exceeds max available %d MB/s (%d active planes)\n",
> -			      data_rate, max_data_rate, num_active_planes);
> +	ret = icl_get_qgv_points(dev_priv, &qi);
> +	if (ret < 0)
> +		return 0;
> +
> +	for (i = 0; i < qi.num_points; i++) {
> +		max_data_rate = icl_max_bw(dev_priv, num_active_planes, i);
> +		/*
> +		 * We need to know which qgv point gives us
> +		 * maximum bandwidth in order to disable SAGV
> +		 * if we find that we exceed SAGV block time
> +		 * with watermarks. By that moment we already
> +		 * have those, as it is calculated earlier in
> +		 * intel_atomic_check,
> +		 */
> +		if (max_data_rate > max_bw) {
> +			max_bw_point = i;
> +			max_bw = max_data_rate;
> +		}
> +		if (max_data_rate >= data_rate)
> +			allowed_points |= 1 << i;
> +		DRM_DEBUG_KMS("QGV point %d: max bw %d required %d\n",
> +			      i, max_data_rate, data_rate);
> +	}
> +
> +	/*
> +	 * BSpec states that we always should have at least one allowed point
> +	 * left, so if we couldn't - simply reject the configuration for obvious
> +	 * reasons.
> +	 */
> +	if (allowed_points == 0) {
> +		DRM_DEBUG_KMS("Could not find any suitable QGV points\n");
>  		return -EINVAL;
>  	}
>  
> +	/*
> +	 * Leave only single point with highest bandwidth, if
> +	 * we can't enable SAGV according to BSpec.
> +	 */
> +	if (!intel_can_enable_sagv(state))
> +		allowed_points = 1 << max_bw_point;
> +
> +	/*
> +	 * We store the ones which need to be masked as that is what PCode
> +	 * actually accepts as a parameter.
> +	 */
> +	state->qgv_points_mask = (~allowed_points) & ((1 << qi.num_points) - 1);
> +
> +	/*
> +	 * If the actual mask had changed we need to make sure that
> +	 * the commits are serialized(in case this is a nomodeset, nonblocking)
> +	 */
> +	if (state->qgv_points_mask != dev_priv->qgv_points_mask) {
> +		ret = intel_atomic_serialize_global_state(state);
> +		if (ret) {
> +			DRM_DEBUG_KMS("Could not serialize global state\n");
> +			return ret;
> +		}
> +	}
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.h b/drivers/gpu/drm/i915/display/intel_bw.h
> index 9db10af012f4..66bf9bc10b73 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.h
> +++ b/drivers/gpu/drm/i915/display/intel_bw.h
> @@ -28,5 +28,7 @@ int intel_bw_init(struct drm_i915_private *dev_priv);
>  int intel_bw_atomic_check(struct intel_atomic_state *state);
>  void intel_bw_crtc_update(struct intel_bw_state *bw_state,
>  			  const struct intel_crtc_state *crtc_state);
> +int icl_pcode_restrict_qgv_points(struct drm_i915_private *dev_priv,
> +				  u32 points_mask);
>  
>  #endif /* __INTEL_BW_H__ */
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index a8168e2aacd5..4aaf66955149 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -14003,6 +14003,48 @@ static void intel_atomic_cleanup_work(struct work_struct *work)
>  	intel_atomic_helper_free_state(i915);
>  }
>  
> +static void intel_qgv_points_mask(struct intel_atomic_state *state)
> +{
> +	struct drm_device *dev = state->base.dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	int ret;
> +	u32 new_mask = dev_priv->qgv_points_mask | state->qgv_points_mask;
> +
> +	/*
> +	 * Restrict required qgv points before updating the configuration.
> +	 * According to BSpec we can't mask and unmask qgv points at the same
> +	 * time. Also masking should be done before updating the configuration
> +	 * and unmasking afterwards.
> +	 */
> +	ret = icl_pcode_restrict_qgv_points(dev_priv, new_mask);
> +	if (ret < 0)
> +		DRM_DEBUG_KMS("Could not restrict required qgv points(%d)\n",

Nit: "Could not mask unusable qgv points"

> +			      ret);
> +	else
> +		dev_priv->qgv_points_mask = new_mask;
> +}
> +
> +static void intel_qgv_points_unmask(struct intel_atomic_state *state)
> +{
> +	struct drm_device *dev = state->base.dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	int ret;
> +	u32 new_mask = dev_priv->qgv_points_mask & state->qgv_points_mask;
> +
> +	/*
> +	 * Allow required qgv points after updating the configuration.
> +	 * According to BSpec we can't mask and unmask qgv points at the same
> +	 * time. Also masking should be done before updating the configuration
> +	 * and unmasking afterwards.
> +	 */
> +	ret = icl_pcode_restrict_qgv_points(dev_priv, new_mask);
> +	if (ret < 0)
> +		DRM_DEBUG_KMS("Could not restrict required qgv points(%d)\n",

Nit: "Could not unmask allowed qgv points"

With those:

Reviewed-by: James Ausmus <james.ausmus@xxxxxxxxx>

> +			      ret);
> +	else
> +		dev_priv->qgv_points_mask = new_mask;
> +}
> +
>  static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  {
>  	struct drm_device *dev = state->base.dev;
> @@ -14030,6 +14072,9 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  		}
>  	}
>  
> +	if ((INTEL_GEN(dev_priv) >= 11))
> +		intel_qgv_points_mask(state);
> +
>  	intel_commit_modeset_disables(state);
>  
>  	/* FIXME: Eventually get rid of our crtc->config pointer */
> @@ -14048,8 +14093,9 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  		 * SKL workaround: bspec recommends we disable the SAGV when we
>  		 * have more then one pipe enabled
>  		 */
> -		if (!intel_can_enable_sagv(state))
> -			intel_disable_sagv(dev_priv);
> +		if (INTEL_GEN(dev_priv) < 11)
> +			if (!intel_can_enable_sagv(state))
> +				intel_disable_sagv(dev_priv);
>  
>  		intel_modeset_verify_disabled(dev_priv, state);
>  	}
> @@ -14127,8 +14173,12 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  	if (state->modeset)
>  		intel_verify_planes(state);
>  
> -	if (state->modeset && intel_can_enable_sagv(state))
> -		intel_enable_sagv(dev_priv);
> +	if (INTEL_GEN(dev_priv) < 11) {
> +		if (state->modeset && intel_can_enable_sagv(state))
> +			intel_enable_sagv(dev_priv);
> +	}
> +	else
> +		intel_qgv_points_unmask(state);
>  
>  	drm_atomic_helper_commit_hw_done(&state->base);
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 40390d855815..8750a34c3e28 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -512,6 +512,9 @@ struct intel_atomic_state {
>  	struct i915_sw_fence commit_ready;
>  
>  	struct llist_node freed;
> +
> +	/* Gen11+ only */
> +	u32 qgv_points_mask;
>  };
>  
>  struct intel_plane_state {
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index c46b339064c0..0b1b641a280f 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1335,6 +1335,8 @@ struct drm_i915_private {
>  		u8 num_planes;
>  	} max_bw[6];
>  
> +	u32 qgv_points_mask;
> +
>  	struct drm_private_obj bw_obj;
>  
>  	struct intel_runtime_pm runtime_pm;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index e24991e54897..1f3402547ba5 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -8869,6 +8869,7 @@ enum {
>  #define   ICL_PCODE_MEM_SUBSYSYSTEM_INFO	0xd
>  #define     ICL_PCODE_MEM_SS_READ_GLOBAL_INFO	(0x0 << 8)
>  #define     ICL_PCODE_MEM_SS_READ_QGV_POINT_INFO(point)	(((point) << 16) | (0x1 << 8))
> +#define   ICL_PCODE_SAGV_DE_MEM_SS_CONFIG	0xe
>  #define   GEN6_PCODE_READ_D_COMP		0x10
>  #define   GEN6_PCODE_WRITE_D_COMP		0x11
>  #define   HSW_PCODE_DE_WRITE_FREQ_REQ		0x17
> @@ -8881,6 +8882,8 @@ enum {
>  #define     GEN9_SAGV_IS_DISABLED		0x1
>  #define     GEN9_SAGV_ENABLE			0x3
>  #define GEN12_PCODE_READ_SAGV_BLOCK_TIME_US	0x23
> +#define GEN11_PCODE_POINTS_RESTRICTED		0x0
> +#define GEN11_PCODE_POINTS_RESTRICTED_MASK	0x1
>  #define GEN6_PCODE_DATA				_MMIO(0x138128)
>  #define   GEN6_PCODE_FREQ_IA_RATIO_SHIFT	8
>  #define   GEN6_PCODE_FREQ_RING_RATIO_SHIFT	16
> -- 
> 2.17.1
> 
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