[v6] drm/i915: Enable second dbuf slice for ICL and TGL
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Message ID 20191108134500.29212-1-stanislav.lisovskiy@intel.com
State New
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  • [v6] drm/i915: Enable second dbuf slice for ICL and TGL
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Commit Message

Lisovskiy, Stanislav Nov. 8, 2019, 1:45 p.m. UTC
Also implemented algorithm for choosing DBuf slice configuration
based on active pipes, pipe ratio as stated in BSpec 12716.

Now pipe allocation still stays proportional to pipe width as before,
however within allowed DBuf slice for this particular configuration.

v2: Remove unneeded check from commit as ddb enabled slices might
    now differ from hw state.

v3: - Added new field "supported_slices" to ddb to separate max
      supported slices vs currently enabled, to avoid confusion.
    - Removed obsolete comments and code related to DBuf(Matthew Roper).
    - Some code style and long line removal(Matthew Roper).
    - Added WARN_ON to new ddb range offset calc function(Matthew Roper).
    - Removed platform specific call to calc pipe ratio from ddb
      allocation function and fixed the return value(Matthew Roper)
    - Refactored DBUF slice allocation table to improve readability
    - Added DBUF slice allocation for TGL as well.
    - ICL(however not TGL) seems to voluntarily enable second DBuf slice
      after pm suspend/resume causing a mismatch failure, because we
      update DBuf slices only if we do a modeset, however this check
      is done always. Fixed it to be done only when modeset for ICL.

v4: - Now enabled slices is not actually a number, but a bitmask,
      because we might need to enable second slice only and number
      of slices would still 1 and that current code doesn't allow.
    - Remove redundant duplicate code to have some unified way of
      enabling dbuf slices instead of hardcoding.

v5: - Fix failing gen9_assert_dbuf_enabled as it was naively thinking
      that we have only one DBUF_CTL slice. Now another version for
      gen11 will check both slices as only second one can be enabled,
      to keep CI happy.

v6: - Removed enabled dbuf assertion completely. Previous code
      was keeping dbuf enabled, even(!) when _dbuf_disable is called.
      Currently we enable/disable dbuf slices based on requrement
      so no point in asserting this here.
    - Removed unnecessary modeset check from verify_wm_state(Matthew Roper)
    - Slices intersection after union is same as final result(Matthew Roper)
    - Moved DBuf slices to intel_device_info(Matthew Roper)
    - Some macros added(Matthew Roper)
    - ddb range is now always less or equal to ddb size - no need for additional
      checks(previously needed as we had some bandwidth checks in there which
      could "suddenly" return ddb_size smaller than it is.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Matthew Roper <matthew.d.roper@intel.com>
Cc: Ville Syrjälä <ville.syrjala@intel.com>
Cc: James Ausmus <james.ausmus@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c  |  26 +-
 .../drm/i915/display/intel_display_power.c    |  98 ++---
 .../drm/i915/display/intel_display_power.h    |   2 +
 drivers/gpu/drm/i915/i915_drv.c               |   5 +
 drivers/gpu/drm/i915/i915_drv.h               |   2 +-
 drivers/gpu/drm/i915/i915_pci.c               |   7 +-
 drivers/gpu/drm/i915/i915_reg.h               |   8 +-
 drivers/gpu/drm/i915/intel_device_info.h      |   1 +
 drivers/gpu/drm/i915/intel_pm.c               | 384 ++++++++++++++++--
 9 files changed, 429 insertions(+), 104 deletions(-)

Comments

Matt Roper Nov. 13, 2019, 9:15 p.m. UTC | #1
On Fri, Nov 08, 2019 at 03:45:00PM +0200, Stanislav Lisovskiy wrote:
> Also implemented algorithm for choosing DBuf slice configuration
> based on active pipes, pipe ratio as stated in BSpec 12716.
> 
> Now pipe allocation still stays proportional to pipe width as before,
> however within allowed DBuf slice for this particular configuration.
> 
> v2: Remove unneeded check from commit as ddb enabled slices might
>     now differ from hw state.
> 
> v3: - Added new field "supported_slices" to ddb to separate max
>       supported slices vs currently enabled, to avoid confusion.
>     - Removed obsolete comments and code related to DBuf(Matthew Roper).
>     - Some code style and long line removal(Matthew Roper).
>     - Added WARN_ON to new ddb range offset calc function(Matthew Roper).
>     - Removed platform specific call to calc pipe ratio from ddb
>       allocation function and fixed the return value(Matthew Roper)
>     - Refactored DBUF slice allocation table to improve readability
>     - Added DBUF slice allocation for TGL as well.
>     - ICL(however not TGL) seems to voluntarily enable second DBuf slice
>       after pm suspend/resume causing a mismatch failure, because we
>       update DBuf slices only if we do a modeset, however this check
>       is done always. Fixed it to be done only when modeset for ICL.
> 
> v4: - Now enabled slices is not actually a number, but a bitmask,
>       because we might need to enable second slice only and number
>       of slices would still 1 and that current code doesn't allow.
>     - Remove redundant duplicate code to have some unified way of
>       enabling dbuf slices instead of hardcoding.
> 
> v5: - Fix failing gen9_assert_dbuf_enabled as it was naively thinking
>       that we have only one DBUF_CTL slice. Now another version for
>       gen11 will check both slices as only second one can be enabled,
>       to keep CI happy.
> 
> v6: - Removed enabled dbuf assertion completely. Previous code
>       was keeping dbuf enabled, even(!) when _dbuf_disable is called.
>       Currently we enable/disable dbuf slices based on requrement
>       so no point in asserting this here.
>     - Removed unnecessary modeset check from verify_wm_state(Matthew Roper)
>     - Slices intersection after union is same as final result(Matthew Roper)
>     - Moved DBuf slices to intel_device_info(Matthew Roper)
>     - Some macros added(Matthew Roper)
>     - ddb range is now always less or equal to ddb size - no need for additional
>       checks(previously needed as we had some bandwidth checks in there which
>       could "suddenly" return ddb_size smaller than it is.
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Cc: Matthew Roper <matthew.d.roper@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@intel.com>
> Cc: James Ausmus <james.ausmus@intel.com>

A handful of comments inline below but most of them are cosmetic, so
I'll leave it up to you whether you agree or not.  The only one I see
that doesn't appear to match the spec is on your TGL pipe A+B dbuf
assignment.

Otherwise,

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


> ---
>  drivers/gpu/drm/i915/display/intel_display.c  |  26 +-
>  .../drm/i915/display/intel_display_power.c    |  98 ++---
>  .../drm/i915/display/intel_display_power.h    |   2 +
>  drivers/gpu/drm/i915/i915_drv.c               |   5 +
>  drivers/gpu/drm/i915/i915_drv.h               |   2 +-
>  drivers/gpu/drm/i915/i915_pci.c               |   7 +-
>  drivers/gpu/drm/i915/i915_reg.h               |   8 +-
>  drivers/gpu/drm/i915/intel_device_info.h      |   1 +
>  drivers/gpu/drm/i915/intel_pm.c               | 384 ++++++++++++++++--
>  9 files changed, 429 insertions(+), 104 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 876fc25968bf..bd7aff675198 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -13387,7 +13387,7 @@ static void verify_wm_state(struct intel_crtc *crtc,
>  
>  	if (INTEL_GEN(dev_priv) >= 11 &&
>  	    hw->ddb.enabled_slices != sw_ddb->enabled_slices)
> -		DRM_ERROR("mismatch in DBUF Slices (expected %u, got %u)\n",
> +		DRM_ERROR("mismatch in DBUF Slices (expected %x, got %x)\n",
>  			  sw_ddb->enabled_slices,
>  			  hw->ddb.enabled_slices);
>  
> @@ -14614,15 +14614,24 @@ static void skl_commit_modeset_enables(struct intel_atomic_state *state)
>  	u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
>  	u8 required_slices = state->wm_results.ddb.enabled_slices;
>  	struct skl_ddb_entry entries[I915_MAX_PIPES] = {};
> +	u8 slices_union = hw_enabled_slices | required_slices;
> +	u8 slices_intersection = required_slices;

We can probably just drop this variable and use required_slices directly
in the one place below.

>  
>  	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i)
>  		/* ignore allocations for crtc's that have been turned off. */
>  		if (new_crtc_state->hw.active)
>  			entries[i] = old_crtc_state->wm.skl.ddb;
>  
> -	/* If 2nd DBuf slice required, enable it here */
> -	if (INTEL_GEN(dev_priv) >= 11 && required_slices > hw_enabled_slices)
> -		icl_dbuf_slices_update(dev_priv, required_slices);
> +	DRM_DEBUG_KMS("DBuf req slices %d hw slices %d\n",
> +		      required_slices, hw_enabled_slices);
> +
> +	/*
> +	 * If some other DBuf slice required, enable it here,
> +	 * as here we only add more slices, but not remove to prevent
> +	 * issues if somebody still uses those.
> +	 */
> +	if (INTEL_GEN(dev_priv) >= 11 && required_slices != hw_enabled_slices)
> +		icl_dbuf_slices_update(dev_priv, slices_union);
>  
>  	/*
>  	 * Whenever the number of active pipes changes, we need to make sure we
> @@ -14681,9 +14690,12 @@ static void skl_commit_modeset_enables(struct intel_atomic_state *state)
>  		}
>  	} while (progress);
>  
> -	/* If 2nd DBuf slice is no more required disable it */
> -	if (INTEL_GEN(dev_priv) >= 11 && required_slices < hw_enabled_slices)
> -		icl_dbuf_slices_update(dev_priv, required_slices);
> +	/*
> +	 * If some other DBuf slice is not needed, disable it here,
> +	 * as here we only remove slices, which are not needed anymore.
> +	 */
> +	if (INTEL_GEN(dev_priv) >= 11 && required_slices != hw_enabled_slices)
> +		icl_dbuf_slices_update(dev_priv, slices_intersection);
>  }
>  
>  static void intel_atomic_helper_free_state(struct drm_i915_private *dev_priv)
> diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
> index ce1b64f4dd44..f406ee5329b0 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.c
> @@ -1031,15 +1031,6 @@ static bool gen9_dc_off_power_well_enabled(struct drm_i915_private *dev_priv,
>  		(I915_READ(DC_STATE_EN) & DC_STATE_EN_UPTO_DC5_DC6_MASK) == 0);
>  }
>  
> -static void gen9_assert_dbuf_enabled(struct drm_i915_private *dev_priv)
> -{
> -	u32 tmp = I915_READ(DBUF_CTL);
> -
> -	WARN((tmp & (DBUF_POWER_STATE | DBUF_POWER_REQUEST)) !=
> -	     (DBUF_POWER_STATE | DBUF_POWER_REQUEST),
> -	     "Unexpected DBuf power power state (0x%08x)\n", tmp);
> -}
> -
>  static void gen9_disable_dc_states(struct drm_i915_private *dev_priv)
>  {
>  	struct intel_cdclk_state cdclk_state = {};
> @@ -1055,8 +1046,6 @@ static void gen9_disable_dc_states(struct drm_i915_private *dev_priv)
>  	/* Can't read out voltage_level so can't use intel_cdclk_changed() */
>  	WARN_ON(intel_cdclk_needs_modeset(&dev_priv->cdclk.hw, &cdclk_state));
>  
> -	gen9_assert_dbuf_enabled(dev_priv);
> -
>  	if (IS_GEN9_LP(dev_priv))
>  		bxt_verify_ddi_phy_power_wells(dev_priv);
>  
> @@ -4254,31 +4243,51 @@ static void gen9_dbuf_disable(struct drm_i915_private *dev_priv)
>  	intel_dbuf_slice_set(dev_priv, DBUF_CTL, false);
>  }
>  
> -static u8 intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
> +int intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
>  {
> -	if (INTEL_GEN(dev_priv) < 11)
> -		return 1;
> -	return 2;
> +	return INTEL_INFO(dev_priv)->supported_slices;
> +}

I'd be inclined to just drop this function and directly access the
device info at the callsites of this function.


> +
> +void icl_dbuf_slices_restore(struct drm_i915_private *dev_priv)
> +{
> +	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
> +
> +	icl_dbuf_slices_update(dev_priv, hw_enabled_slices);
>  }

Minor nitpick:  you're using this for a lot more than just "restoring"
now.  It's more a matter of you committing software state into the
hardware.  A name like icl_dbuf_slices_commit or icl_program_dbuf_slices
might be slightly more intuitive?

>  
>  void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
>  			    u8 req_slices)
>  {
> -	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
> -	bool ret;
> +	bool ret = true;
> +	int i;
> +	int max_slices = intel_dbuf_max_slices(dev_priv);
>  
> -	if (req_slices > intel_dbuf_max_slices(dev_priv)) {
> +	if (hweight8(req_slices) > intel_dbuf_max_slices(dev_priv)) {
>  		DRM_ERROR("Invalid number of dbuf slices requested\n");
>  		return;
>  	}
>  
> -	if (req_slices == hw_enabled_slices || req_slices == 0)
> -		return;
> +	DRM_DEBUG_KMS("Updating dbuf slices to %x\n", req_slices);
>  
> -	if (req_slices > hw_enabled_slices)
> -		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, true);
> -	else
> -		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, false);
> +	for (i = 0; i < max_slices; i++) {
> +		int slice_bit = BIT(i);
> +		bool slice_set = (slice_bit & req_slices) != 0;
> +
> +		switch (slice_bit) {
> +		case DBUF_S1_BIT:
> +			ret = ret && intel_dbuf_slice_set(dev_priv,
> +							  DBUF_CTL_S1,
> +							  slice_set);
> +			break;
> +		case DBUF_S2_BIT:
> +			ret = ret && intel_dbuf_slice_set(dev_priv,
> +							  DBUF_CTL_S2,
> +							  slice_set);
> +			break;
> +		default:
> +			MISSING_CASE(slice_bit);
> +		}
> +	}
>  
>  	if (ret)
>  		dev_priv->wm.skl_hw.ddb.enabled_slices = req_slices;
> @@ -4286,40 +4295,21 @@ void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
>  
>  static void icl_dbuf_enable(struct drm_i915_private *dev_priv)
>  {
> -	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) | DBUF_POWER_REQUEST);
> -	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) | DBUF_POWER_REQUEST);
> -	POSTING_READ(DBUF_CTL_S2);
> -
> -	udelay(10);
> -
> -	if (!(I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
> -	    !(I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
> -		DRM_ERROR("DBuf power enable timeout\n");
> -	else
> -		/*
> -		 * FIXME: for now pretend that we only have 1 slice, see
> -		 * intel_enabled_dbuf_slices_num().
> -		 */
> -		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
> +	/*
> +	 * Just power up 1 slice, we will
> +	 * figure out later which slices we have and what we need.
> +	 */
> +	dev_priv->wm.skl_hw.ddb.enabled_slices = DBUF_S1_BIT;
> +	icl_dbuf_slices_restore(dev_priv);
>  }
>  
>  static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
>  {
> -	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) & ~DBUF_POWER_REQUEST);
> -	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) & ~DBUF_POWER_REQUEST);
> -	POSTING_READ(DBUF_CTL_S2);
> -
> -	udelay(10);
> -
> -	if ((I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
> -	    (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
> -		DRM_ERROR("DBuf power disable timeout!\n");
> -	else
> -		/*
> -		 * FIXME: for now pretend that the first slice is always
> -		 * enabled, see intel_enabled_dbuf_slices_num().
> -		 */
> -		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
> +	/*
> +	 * Disable all slices
> +	 */
> +	dev_priv->wm.skl_hw.ddb.enabled_slices = 0;
> +	icl_dbuf_slices_restore(dev_priv);
>  }
>  
>  static void icl_mbus_init(struct drm_i915_private *dev_priv)
> diff --git a/drivers/gpu/drm/i915/display/intel_display_power.h b/drivers/gpu/drm/i915/display/intel_display_power.h
> index 1da04f3e0fb3..c5afb3129571 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.h
> @@ -311,8 +311,10 @@ intel_display_power_put_async(struct drm_i915_private *i915,
>  	for ((wf) = intel_display_power_get((i915), (domain)); (wf); \
>  	     intel_display_power_put_async((i915), (domain), (wf)), (wf) = 0)
>  
> +int intel_dbuf_max_slices(struct drm_i915_private *dev_priv);
>  void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
>  			    u8 req_slices);
> +void icl_dbuf_slices_restore(struct drm_i915_private *dev_priv);
>  
>  void chv_phy_powergate_lanes(struct intel_encoder *encoder,
>  			     bool override, unsigned int mask);
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 82e4e6bf08c3..0307aec2c928 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -51,6 +51,7 @@
>  #include "display/intel_bw.h"
>  #include "display/intel_cdclk.h"
>  #include "display/intel_display_types.h"
> +#include "display/intel_display_power.h"
>  #include "display/intel_dp.h"
>  #include "display/intel_fbdev.h"
>  #include "display/intel_hotplug.h"
> @@ -2588,6 +2589,10 @@ static int intel_runtime_resume(struct device *kdev)
>  	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
>  		ret = vlv_resume_prepare(dev_priv, true);
>  
> +	/* Weird hack to fix ICL hardware bug, as it resets DBUF slices reg */
> +	if (INTEL_GEN(dev_priv) == 11)
> +		icl_dbuf_slices_restore(dev_priv);

Has anyone tried this on EHL yet?  I'm wondering if this should be
IS_ICELAKE().

> +
>  	intel_uncore_runtime_resume(&dev_priv->uncore);
>  
>  	intel_runtime_pm_enable_interrupts(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 7e0f67babe20..a396977c9c2d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -804,7 +804,7 @@ static inline bool skl_ddb_entry_equal(const struct skl_ddb_entry *e1,
>  }
>  
>  struct skl_ddb_allocation {
> -	u8 enabled_slices; /* GEN11 has configurable 2 slices */
> +	u8 enabled_slices;   /* Bitmask of currently enabled DBuf slices */
>  };
>  
>  struct skl_ddb_values {
> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> index 1bb701d32a5d..39c3db4ef7da 100644
> --- a/drivers/gpu/drm/i915/i915_pci.c
> +++ b/drivers/gpu/drm/i915/i915_pci.c
> @@ -614,7 +614,8 @@ static const struct intel_device_info intel_cherryview_info = {
>  	.has_gt_uc = 1, \
>  	.display.has_hdcp = 1, \
>  	.display.has_ipc = 1, \
> -	.ddb_size = 896
> +	.ddb_size = 896, \
> +	.supported_slices = 1
>  
>  #define SKL_PLATFORM \
>  	GEN9_FEATURES, \
> @@ -682,12 +683,14 @@ static const struct intel_device_info intel_broxton_info = {
>  	GEN9_LP_FEATURES,
>  	PLATFORM(INTEL_BROXTON),
>  	.ddb_size = 512,
> +	.supported_slices = 1,

If you put this in GEN9_LP_FEATURES it will take care of both BXT and
GLK.

>  };
>  
>  static const struct intel_device_info intel_geminilake_info = {
>  	GEN9_LP_FEATURES,
>  	PLATFORM(INTEL_GEMINILAKE),
>  	.ddb_size = 1024,
> +	.supported_slices = 1,
>  	GLK_COLORS,
>  };
>  
> @@ -737,6 +740,7 @@ static const struct intel_device_info intel_coffeelake_gt3_info = {
>  	GEN9_FEATURES, \
>  	GEN(10), \
>  	.ddb_size = 1024, \
> +	.supported_slices = 1, \
>  	.display.has_dsc = 1, \
>  	.has_coherent_ggtt = false, \
>  	GLK_COLORS
> @@ -773,6 +777,7 @@ static const struct intel_device_info intel_cannonlake_info = {
>  	}, \
>  	GEN(11), \
>  	.ddb_size = 2048, \
> +	.supported_slices = 2, \
>  	.has_logical_ring_elsq = 1, \
>  	.color = { .degamma_lut_size = 33, .gamma_lut_size = 262145 }
>  
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a607ea520829..fba5731063d8 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7734,9 +7734,11 @@ enum {
>  #define DISP_ARB_CTL2	_MMIO(0x45004)
>  #define  DISP_DATA_PARTITION_5_6	(1 << 6)
>  #define  DISP_IPC_ENABLE		(1 << 3)
> -#define DBUF_CTL	_MMIO(0x45008)
> -#define DBUF_CTL_S1	_MMIO(0x45008)
> -#define DBUF_CTL_S2	_MMIO(0x44FE8)
> +#define DBUF_S1_BIT			BIT(0)
> +#define DBUF_S2_BIT			BIT(1)
> +#define DBUF_CTL			_MMIO(0x45008)
> +#define DBUF_CTL_S1			_MMIO(0x45008)
> +#define DBUF_CTL_S2			_MMIO(0x44FE8)
>  #define  DBUF_POWER_REQUEST		(1 << 31)
>  #define  DBUF_POWER_STATE		(1 << 30)
>  #define GEN7_MSG_CTL	_MMIO(0x45010)
> diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
> index 4bdf8a6cfb47..ba34e1a5c591 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.h
> +++ b/drivers/gpu/drm/i915/intel_device_info.h
> @@ -180,6 +180,7 @@ struct intel_device_info {
>  	} display;
>  
>  	u16 ddb_size; /* in blocks */
> +	u8 supported_slices; /* number of DBuf slices */

Since slice/subslice terminology is used on the GT side, it might be
worth naming this "dbuf_slices" instead to avoid any confusion.

>  
>  	/* Register offsets for the various display pipes and transcoders */
>  	int pipe_offsets[I915_MAX_TRANSCODERS];
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 2d389e437e87..b6627c845f1c 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3586,24 +3586,20 @@ bool ilk_disable_lp_wm(struct drm_device *dev)
>  	return _ilk_disable_lp_wm(dev_priv, WM_DIRTY_LP_ALL);
>  }
>  
> -static u8 intel_enabled_dbuf_slices_num(struct drm_i915_private *dev_priv)
> +static u8 intel_enabled_dbuf_slices(struct drm_i915_private *dev_priv)
>  {
> -	u8 enabled_slices;
> -
> -	/* Slice 1 will always be enabled */
> -	enabled_slices = 1;
> +	u8 enabled_slices = 0;
>  
>  	/* Gen prior to GEN11 have only one DBuf slice */
>  	if (INTEL_GEN(dev_priv) < 11)
> -		return enabled_slices;
> +		return DBUF_S1_BIT;
>  
> -	/*
> -	 * FIXME: for now we'll only ever use 1 slice; pretend that we have
> -	 * only that 1 slice enabled until we have a proper way for on-demand
> -	 * toggling of the second slice.
> -	 */
> -	if (0 && I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
> -		enabled_slices++;
> +	/* Check if second DBuf slice is enabled */
> +	if (I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE)
> +		enabled_slices |= DBUF_S1_BIT;
> +
> +	if (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
> +		enabled_slices |= DBUF_S2_BIT;
>  
>  	return enabled_slices;
>  }
> @@ -3812,36 +3808,38 @@ static u16 intel_get_ddb_size(struct drm_i915_private *dev_priv,
>  			      const int num_active,
>  			      struct skl_ddb_allocation *ddb)
>  {
> -	const struct drm_display_mode *adjusted_mode;
> -	u64 total_data_bw;
>  	u16 ddb_size = INTEL_INFO(dev_priv)->ddb_size;
> -
>  	WARN_ON(ddb_size == 0);
>  
>  	if (INTEL_GEN(dev_priv) < 11)
>  		return ddb_size - 4; /* 4 blocks for bypass path allocation */
>  
> -	adjusted_mode = &crtc_state->hw.adjusted_mode;
> -	total_data_bw = total_data_rate * drm_mode_vrefresh(adjusted_mode);
> +	return ddb_size;
> +}
>  
> -	/*
> -	 * 12GB/s is maximum BW supported by single DBuf slice.
> -	 *
> -	 * FIXME dbuf slice code is broken:
> -	 * - must wait for planes to stop using the slice before powering it off
> -	 * - plane straddling both slices is illegal in multi-pipe scenarios
> -	 * - should validate we stay within the hw bandwidth limits
> -	 */
> -	if (0 && (num_active > 1 || total_data_bw >= GBps(12))) {
> -		ddb->enabled_slices = 2;
> -	} else {
> -		ddb->enabled_slices = 1;
> -		ddb_size /= 2;
> -	}
> +/*
> + * Calculate initial DBuf slice offset, based on slice size
> + * and mask(i.e if slice size is 1024 and second slice is enabled
> + * offset would be 1024)
> + */
> +static u32 skl_get_first_dbuf_slice_offset(u32 dbuf_slice_mask,
> +					   u32 slice_size, u32 ddb_size)
> +{
> +	u32 offset = 0;
>  
> -	return ddb_size;
> +	if (!dbuf_slice_mask)
> +		return 0;
> +
> +	offset = (ffs(dbuf_slice_mask) - 1) * slice_size;
> +
> +	WARN_ON(offset >= ddb_size);
> +	return offset;
>  }
>  
> +static u32 i915_get_allowed_dbuf_mask(struct drm_i915_private *dev_priv,
> +				      int pipe, u32 active_pipes,
> +				      const struct intel_crtc_state *crtc_state);
> +
>  static void
>  skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
>  				   const struct intel_crtc_state *crtc_state,
> @@ -3857,7 +3855,14 @@ skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
>  	u32 pipe_width = 0, total_width = 0, width_before_pipe = 0;
>  	enum pipe for_pipe = to_intel_crtc(for_crtc)->pipe;
>  	u16 ddb_size;
> +	u32 ddb_range_size;
>  	u32 i;
> +	u32 dbuf_slice_mask;
> +	u32 active_pipes;
> +	u32 offset;
> +	u32 slice_size;
> +	u32 total_slice_mask;
> +	u32 start, end;
>  
>  	if (WARN_ON(!state) || !crtc_state->hw.active) {
>  		alloc->start = 0;
> @@ -3866,14 +3871,23 @@ skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
>  		return;
>  	}
>  
> -	if (intel_state->active_pipe_changes)
> +	if (intel_state->active_pipe_changes) {
>  		*num_active = hweight8(intel_state->active_pipes);
> -	else
> +		active_pipes = intel_state->active_pipes;
> +	} else {
>  		*num_active = hweight8(dev_priv->active_pipes);
> +		active_pipes = dev_priv->active_pipes;
> +	}
>  
>  	ddb_size = intel_get_ddb_size(dev_priv, crtc_state, total_data_rate,
>  				      *num_active, ddb);
>  
> +	DRM_DEBUG_KMS("Got total ddb size %d\n", ddb_size);
> +
> +	slice_size = ddb_size / INTEL_INFO(dev_priv)->supported_slices;
> +
> +	DRM_DEBUG_KMS("Got DBuf slice size %d\n", slice_size);
> +
>  	/*
>  	 * If the state doesn't change the active CRTC's or there is no
>  	 * modeset request, then there's no need to recalculate;
> @@ -3891,20 +3905,70 @@ skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
>  		return;
>  	}
>  
> +	/*
> +	 * Get allowed DBuf slices for correspondent pipe and platform.
> +	 */
> +	dbuf_slice_mask = i915_get_allowed_dbuf_mask(dev_priv, for_pipe,
> +						     active_pipes, crtc_state);
> +
> +	DRM_DEBUG_KMS("DBuf slice mask %x pipe %d active pipes %x\n",
> +		      dbuf_slice_mask,
> +		      for_pipe, active_pipes);
> +
> +	/*
> +	 * Figure out at which DBuf slice we start, i.e if we start at Dbuf S2
> +	 * and slice size is 1024, the offset would be 1024
> +	 */
> +	offset = skl_get_first_dbuf_slice_offset(dbuf_slice_mask,
> +						 slice_size, ddb_size);
> +
> +	/*
> +	 * Figure out total size of allowed DBuf slices, which is basically
> +	 * a number of allowed slices for that pipe multiplied by slice size.
> +	 * Inside of this
> +	 * range ddb entries are still allocated in proportion to display width.
> +	 */
> +	ddb_range_size = hweight8(dbuf_slice_mask) * slice_size;
> +
>  	/*
>  	 * Watermark/ddb requirement highly depends upon width of the
>  	 * framebuffer, So instead of allocating DDB equally among pipes
>  	 * distribute DDB based on resolution/width of the display.
>  	 */
> +	total_slice_mask = dbuf_slice_mask;
>  	for_each_new_intel_crtc_in_state(intel_state, crtc, crtc_state, i) {
>  		const struct drm_display_mode *adjusted_mode =
>  			&crtc_state->hw.adjusted_mode;
>  		enum pipe pipe = crtc->pipe;
>  		int hdisplay, vdisplay;
> +		u32 pipe_dbuf_slice_mask = \
> +			i915_get_allowed_dbuf_mask(dev_priv,
> +						pipe,
> +						active_pipes,
> +						crtc_state);
>  
>  		if (!crtc_state->hw.enable)
>  			continue;
>  
> +		/*
> +		 * According to BSpec pipe can share one dbuf slice with another
> +		 * pipes or pipe can use multiple dbufs, in both cases we
> +		 * account for other pipes only if they have exactly same mask.
> +		 * However we need to account how many slices we should enable
> +		 * in total.
> +		 */
> +		total_slice_mask |= pipe_dbuf_slice_mask;
> +
> +		/*
> +		 * Do not account pipes using other slice sets
> +		 * luckily as of current BSpec slice sets do not partially
> +		 * intersect(pipes share either same one slice or same slice set
> +		 * i.e no partial intersection), so it is enough to check for
> +		 * equality for now.
> +		 */
> +		if (dbuf_slice_mask != pipe_dbuf_slice_mask)
> +			continue;
> +
>  		drm_mode_get_hv_timing(adjusted_mode, &hdisplay, &vdisplay);
>  		total_width += hdisplay;
>  
> @@ -3914,8 +3978,19 @@ skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
>  			pipe_width = hdisplay;
>  	}
>  
> -	alloc->start = ddb_size * width_before_pipe / total_width;
> -	alloc->end = ddb_size * (width_before_pipe + pipe_width) / total_width;
> +	ddb->enabled_slices = total_slice_mask;
> +
> +	start = ddb_range_size * width_before_pipe / total_width;
> +	end = ddb_range_size * (width_before_pipe + pipe_width) / total_width;
> +
> +	alloc->start = offset + start;
> +	alloc->end = offset + end;
> +
> +	DRM_DEBUG_KMS("Pipe %d ddb %d-%d\n", for_pipe,
> +		      alloc->start, alloc->end);
> +	DRM_DEBUG_KMS("Enabled ddb slices mask %x num supported %d\n",
> +		      ddb->enabled_slices,
> +		      INTEL_INFO(dev_priv)->supported_slices);
>  }
>  
>  static int skl_compute_wm_params(const struct intel_crtc_state *crtc_state,
> @@ -4036,7 +4111,8 @@ void skl_pipe_ddb_get_hw_state(struct intel_crtc *crtc,
>  void skl_ddb_get_hw_state(struct drm_i915_private *dev_priv,
>  			  struct skl_ddb_allocation *ddb /* out */)
>  {
> -	ddb->enabled_slices = intel_enabled_dbuf_slices_num(dev_priv);
> +	ddb->enabled_slices = intel_enabled_dbuf_slices(dev_priv);
> +	DRM_DEBUG_KMS("Got hw dbuf slices mask %x\n", ddb->enabled_slices);
>  }
>  
>  /*
> @@ -4164,6 +4240,238 @@ skl_get_total_relative_data_rate(struct intel_crtc_state *crtc_state,
>  	return total_data_rate;
>  }
>  
> +uint_fixed_16_16_t
> +skl_pipe_downscale_amount(const struct intel_crtc_state *crtc_state)

Since this is only used on gen11+, should it be named
icl_pipe_downscale_amount?

> +{
> +	u32 src_w, src_h, dst_w, dst_h;
> +	uint_fixed_16_16_t fp_w_ratio, fp_h_ratio;
> +	uint_fixed_16_16_t downscale_h, downscale_w;
> +	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
> +
> +	src_w = crtc_state->pipe_src_w;
> +	src_h = crtc_state->pipe_src_h;
> +	dst_w = adjusted_mode->crtc_hdisplay;
> +	dst_h = adjusted_mode->crtc_vdisplay;
> +
> +	fp_w_ratio = div_fixed16(src_w, dst_w);
> +	fp_h_ratio = div_fixed16(src_h, dst_h);
> +	downscale_w = max_fixed16(fp_w_ratio, u32_to_fixed16(1));
> +	downscale_h = max_fixed16(fp_h_ratio, u32_to_fixed16(1));
> +
> +	return mul_fixed16(downscale_w, downscale_h);
> +}
> +
> +uint_fixed_16_16_t
> +icl_get_pipe_ratio(const struct intel_crtc_state *crtc_state)
> +{
> +	struct drm_plane *plane;
> +	const struct drm_plane_state *drm_plane_state;
> +	uint_fixed_16_16_t pipe_downscale, pipe_ratio;
> +	uint_fixed_16_16_t max_downscale = u32_to_fixed16(1);
> +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> +
> +	if (!crtc_state->uapi.enable)
> +		return max_downscale;
> +
> +	drm_atomic_crtc_state_for_each_plane_state(plane, drm_plane_state, &crtc_state->uapi) {
> +		uint_fixed_16_16_t plane_downscale;
> +		const struct intel_plane_state *plane_state =
> +			to_intel_plane_state(drm_plane_state);
> +
> +		if (!intel_wm_plane_visible(crtc_state, plane_state))
> +			continue;
> +
> +		plane_downscale = skl_plane_downscale_amount(crtc_state, plane_state);
> +
> +		DRM_DEBUG_KMS("Plane %d downscale amount %d.%d\n",
> +			      to_intel_plane(plane)->id,
> +			      plane_downscale.val >> 16,
> +			      plane_downscale.val & 0xffff);
> +
> +		max_downscale = max_fixed16(plane_downscale, max_downscale);
> +	}
> +
> +
> +	pipe_downscale = skl_pipe_downscale_amount(crtc_state);
> +
> +	DRM_DEBUG_KMS("Pipe %d downscale amount %d.%d\n",
> +		       crtc->pipe, pipe_downscale.val >> 16,
> +		       pipe_downscale.val & 0xffff);
> +
> +	pipe_downscale = mul_fixed16(pipe_downscale, max_downscale);
> +
> +	/* Convert result to percentage */
> +	pipe_ratio = u32_to_fixed16(100 * div_round_up_u32_fixed16(1, pipe_downscale));

I think the math here is correct, but it gets a bit confusing since we
work with different terms than the bspec steps (e.g., using max plane
downscale rather than minimum plane ratio and such)...maybe a few extra
comments in this function would help reduce confusion?

> +
> +	DRM_DEBUG_KMS("Pipe %d ratio %d.%d\n", crtc->pipe,
> +		      pipe_ratio.val >> 16, pipe_ratio.val & 0xffff);
> +
> +	return pipe_ratio;
> +}
> +
> +struct dbuf_slice_conf_entry {
> +	u32 dbuf_mask[I915_MAX_PIPES];
> +	u32 active_pipes;
> +};
> +
> +
> +#define ICL_PIPE_A_DBUF_SLICES(DBuf1)  \
> +	{ { DBuf1, 0, 0, 0 }, BIT(PIPE_A) }
> +#define ICL_PIPE_B_DBUF_SLICES(DBuf1)  \
> +	{ { 0, DBuf1, 0, 0 }, BIT(PIPE_B) }
> +#define ICL_PIPE_C_DBUF_SLICES(DBuf1)  \
> +	{ { 0, 0, DBuf1, 0 }, BIT(PIPE_C) }
> +#define ICL_PIPE_D_DBUF_SLICES(DBuf1)  \
> +	{ { 0, 0, 0, DBuf1 }, BIT(PIPE_D) }

We'd probably want to call this (and the others that mention pipe D)
TGL_* since they aren't actually relevant until gen12.

> +#define ICL_PIPE_AB_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { DBuf1, DBuf2, 0, 0 }, BIT(PIPE_A) | BIT(PIPE_B) }
> +#define ICL_PIPE_BC_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { 0, DBuf1, DBuf2, 0 }, BIT(PIPE_B) | BIT(PIPE_C) }
> +#define ICL_PIPE_BD_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { 0, DBuf1, 0, DBuf2 }, BIT(PIPE_B) | BIT(PIPE_D) }
> +#define ICL_PIPE_AC_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { DBuf1, 0, DBuf2, 0 }, BIT(PIPE_A) | BIT(PIPE_C) }
> +#define ICL_PIPE_AD_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { DBuf1, 0, 0, DBuf2 }, BIT(PIPE_A) | BIT(PIPE_D) }
> +#define ICL_PIPE_CD_DBUF_SLICES(DBuf1, DBuf2)   \
> +	{ { 0, 0, DBuf1, DBuf2 }, BIT(PIPE_C) | BIT(PIPE_D) }
> +#define ICL_PIPE_ABC_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
> +	{ { DBuf1, DBuf2, DBuf3, 0 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_C) }
> +#define ICL_PIPE_ACD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
> +	{ { DBuf1, 0, DBuf2, DBuf3 }, BIT(PIPE_A) | BIT(PIPE_C) | BIT(PIPE_D) }
> +#define ICL_PIPE_BCD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
> +	{ { 0, DBuf1, DBuf2, DBuf3 }, BIT(PIPE_B) | BIT(PIPE_C) | BIT(PIPE_D) }
> +#define ICL_PIPE_ABD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
> +	{ { DBuf1, DBuf2, 0, DBuf3 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_D) }
> +#define ICL_PIPE_ABC_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
> +	{ { DBuf1, DBuf2, DBuf3, 0 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_C) }
> +#define ICL_PIPE_ABCD_DBUF_SLICES(DBuf1, DBuf2, DBuf3, DBuf4)  \
> +	{ { DBuf1, DBuf2, DBuf3, DBuf4 }, BIT(PIPE_A) | BIT(PIPE_B) | \
> +					  BIT(PIPE_C) | BIT(PIPE_D) }
> +
> +/*
> + * Table taken from Bspec 12716
> + * Pipes do have some preferred DBuf slice affinity,
> + * plus there are some hardcoded requirements on how
> + * those should be distributed for multipipe scenarios.
> + * For more DBuf slices algorithm can get even more messy
> + * and less readable, so decided to use a table almost
> + * as is from BSpec itself - that way it is at least easier
> + * to compare, change and check.
> + */
> +struct dbuf_slice_conf_entry icl_allowed_dbufs[] = {
> +{ { 0, 0, 0, 0 }, 0 },
> +ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
> +ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT),                /* for pipe ratio >= 88.8 */
> +ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
> +ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT),                /* for pipe ratio >= 88.8 */
> +ICL_PIPE_C_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
> +ICL_PIPE_C_DBUF_SLICES(DBUF_S2_BIT),                /* for pipe ratio >= 88.8 */
> +ICL_PIPE_AB_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_AC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_BC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_ABC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
> +};
> +
> +/*
> + * Table taken from Bspec 49255
> + * Pipes do have some preferred DBuf slice affinity,
> + * plus there are some hardcoded requirements on how
> + * those should be distributed for multipipe scenarios.
> + * For more DBuf slices algorithm can get even more messy
> + * and less readable, so decided to use a table almost
> + * as is from BSpec itself - that way it is at least easier
> + * to compare, change and check.
> + */
> +struct dbuf_slice_conf_entry tgl_allowed_dbufs[] = {
> +{ { 0, 0, 0, 0 }, 0 },
> +ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
> +ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
> +ICL_PIPE_C_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
> +ICL_PIPE_D_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
> +ICL_PIPE_AB_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),

The column order in the bspec is bizarre (D, C, A, B), but isn't this
one backwards?  Pipe A gets S2, pipe B gets S1?  Or do we think this is
a bspec mistake (it does seem unusual)?

> +ICL_PIPE_AC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_BC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_AD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_BD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_CD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_ABD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_ABC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
> +ICL_PIPE_ACD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
> +ICL_PIPE_BCD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
> +ICL_PIPE_ABCD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
> +};
> +
> +/*
> + * This function finds an entry with same enabled pipe configuration and
> + * returns correspondent DBuf slice mask as stated in BSpec for particular
> + * platform.
> + */
> +static u32 icl_get_allowed_dbuf_mask(int pipe,
> +				     u32 active_pipes,
> +				     const struct intel_crtc_state *crtc_state)
> +{
> +	int i;
> +	uint_fixed_16_16_t pipe_ratio;
> +
> +	/*
> +	 * Calculate pipe ratio as stated in BSpec 28692
> +	 */
> +	pipe_ratio = icl_get_pipe_ratio(crtc_state);
> +
> +	for (i = 0; i < ARRAY_SIZE(icl_allowed_dbufs); i++) {
> +		if (icl_allowed_dbufs[i].active_pipes == active_pipes) {
> +			if (hweight32(active_pipes) == 1) {
> +				/*
> +				 * According to BSpec 12716: if ratio >= 88.8
> +				 * always use single dbuf slice.
> +				 */
> +				if (pipe_ratio.val >= div_fixed16(888, 10).val)
> +					++i;
> +			}
> +			return icl_allowed_dbufs[i].dbuf_mask[pipe];
> +		}
> +	}
> +	return 0;
> +}
> +
> +/*
> + * This function finds an entry with same enabled pipe configuration and
> + * returns correspondent DBuf slice mask as stated in BSpec for particular
> + * platform.
> + */
> +static u32 tgl_get_allowed_dbuf_mask(int pipe,
> +				     u32 active_pipes,
> +				     const struct intel_crtc_state *crtc_state)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(tgl_allowed_dbufs); i++) {
> +		if (tgl_allowed_dbufs[i].active_pipes == active_pipes)
> +			return tgl_allowed_dbufs[i].dbuf_mask[pipe];
> +	}
> +	return 0;
> +}
> +
> +u32 i915_get_allowed_dbuf_mask(struct drm_i915_private *dev_priv,
> +				      int pipe, u32 active_pipes,
> +				      const struct intel_crtc_state *crtc_state)
> +{
> +	if (IS_GEN(dev_priv, 11))
> +		return icl_get_allowed_dbuf_mask(pipe,
> +						 active_pipes,
> +						 crtc_state);
> +	else if (IS_GEN(dev_priv, 12))
> +		return tgl_get_allowed_dbuf_mask(pipe,
> +						 active_pipes,
> +						 crtc_state);
> +	/*
> +	 * For anything else just return one slice yet.
> +	 * Should be extended for other platforms.
> +	 */
> +	return DBUF_S1_BIT;
> +}
> +
>  static u64
>  icl_get_total_relative_data_rate(struct intel_crtc_state *crtc_state,
>  				 u64 *plane_data_rate)
> -- 
> 2.17.1
>

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 876fc25968bf..bd7aff675198 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -13387,7 +13387,7 @@  static void verify_wm_state(struct intel_crtc *crtc,
 
 	if (INTEL_GEN(dev_priv) >= 11 &&
 	    hw->ddb.enabled_slices != sw_ddb->enabled_slices)
-		DRM_ERROR("mismatch in DBUF Slices (expected %u, got %u)\n",
+		DRM_ERROR("mismatch in DBUF Slices (expected %x, got %x)\n",
 			  sw_ddb->enabled_slices,
 			  hw->ddb.enabled_slices);
 
@@ -14614,15 +14614,24 @@  static void skl_commit_modeset_enables(struct intel_atomic_state *state)
 	u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
 	u8 required_slices = state->wm_results.ddb.enabled_slices;
 	struct skl_ddb_entry entries[I915_MAX_PIPES] = {};
+	u8 slices_union = hw_enabled_slices | required_slices;
+	u8 slices_intersection = required_slices;
 
 	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i)
 		/* ignore allocations for crtc's that have been turned off. */
 		if (new_crtc_state->hw.active)
 			entries[i] = old_crtc_state->wm.skl.ddb;
 
-	/* If 2nd DBuf slice required, enable it here */
-	if (INTEL_GEN(dev_priv) >= 11 && required_slices > hw_enabled_slices)
-		icl_dbuf_slices_update(dev_priv, required_slices);
+	DRM_DEBUG_KMS("DBuf req slices %d hw slices %d\n",
+		      required_slices, hw_enabled_slices);
+
+	/*
+	 * If some other DBuf slice required, enable it here,
+	 * as here we only add more slices, but not remove to prevent
+	 * issues if somebody still uses those.
+	 */
+	if (INTEL_GEN(dev_priv) >= 11 && required_slices != hw_enabled_slices)
+		icl_dbuf_slices_update(dev_priv, slices_union);
 
 	/*
 	 * Whenever the number of active pipes changes, we need to make sure we
@@ -14681,9 +14690,12 @@  static void skl_commit_modeset_enables(struct intel_atomic_state *state)
 		}
 	} while (progress);
 
-	/* If 2nd DBuf slice is no more required disable it */
-	if (INTEL_GEN(dev_priv) >= 11 && required_slices < hw_enabled_slices)
-		icl_dbuf_slices_update(dev_priv, required_slices);
+	/*
+	 * If some other DBuf slice is not needed, disable it here,
+	 * as here we only remove slices, which are not needed anymore.
+	 */
+	if (INTEL_GEN(dev_priv) >= 11 && required_slices != hw_enabled_slices)
+		icl_dbuf_slices_update(dev_priv, slices_intersection);
 }
 
 static void intel_atomic_helper_free_state(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index ce1b64f4dd44..f406ee5329b0 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -1031,15 +1031,6 @@  static bool gen9_dc_off_power_well_enabled(struct drm_i915_private *dev_priv,
 		(I915_READ(DC_STATE_EN) & DC_STATE_EN_UPTO_DC5_DC6_MASK) == 0);
 }
 
-static void gen9_assert_dbuf_enabled(struct drm_i915_private *dev_priv)
-{
-	u32 tmp = I915_READ(DBUF_CTL);
-
-	WARN((tmp & (DBUF_POWER_STATE | DBUF_POWER_REQUEST)) !=
-	     (DBUF_POWER_STATE | DBUF_POWER_REQUEST),
-	     "Unexpected DBuf power power state (0x%08x)\n", tmp);
-}
-
 static void gen9_disable_dc_states(struct drm_i915_private *dev_priv)
 {
 	struct intel_cdclk_state cdclk_state = {};
@@ -1055,8 +1046,6 @@  static void gen9_disable_dc_states(struct drm_i915_private *dev_priv)
 	/* Can't read out voltage_level so can't use intel_cdclk_changed() */
 	WARN_ON(intel_cdclk_needs_modeset(&dev_priv->cdclk.hw, &cdclk_state));
 
-	gen9_assert_dbuf_enabled(dev_priv);
-
 	if (IS_GEN9_LP(dev_priv))
 		bxt_verify_ddi_phy_power_wells(dev_priv);
 
@@ -4254,31 +4243,51 @@  static void gen9_dbuf_disable(struct drm_i915_private *dev_priv)
 	intel_dbuf_slice_set(dev_priv, DBUF_CTL, false);
 }
 
-static u8 intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
+int intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
 {
-	if (INTEL_GEN(dev_priv) < 11)
-		return 1;
-	return 2;
+	return INTEL_INFO(dev_priv)->supported_slices;
+}
+
+void icl_dbuf_slices_restore(struct drm_i915_private *dev_priv)
+{
+	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
+
+	icl_dbuf_slices_update(dev_priv, hw_enabled_slices);
 }
 
 void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 			    u8 req_slices)
 {
-	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
-	bool ret;
+	bool ret = true;
+	int i;
+	int max_slices = intel_dbuf_max_slices(dev_priv);
 
-	if (req_slices > intel_dbuf_max_slices(dev_priv)) {
+	if (hweight8(req_slices) > intel_dbuf_max_slices(dev_priv)) {
 		DRM_ERROR("Invalid number of dbuf slices requested\n");
 		return;
 	}
 
-	if (req_slices == hw_enabled_slices || req_slices == 0)
-		return;
+	DRM_DEBUG_KMS("Updating dbuf slices to %x\n", req_slices);
 
-	if (req_slices > hw_enabled_slices)
-		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, true);
-	else
-		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, false);
+	for (i = 0; i < max_slices; i++) {
+		int slice_bit = BIT(i);
+		bool slice_set = (slice_bit & req_slices) != 0;
+
+		switch (slice_bit) {
+		case DBUF_S1_BIT:
+			ret = ret && intel_dbuf_slice_set(dev_priv,
+							  DBUF_CTL_S1,
+							  slice_set);
+			break;
+		case DBUF_S2_BIT:
+			ret = ret && intel_dbuf_slice_set(dev_priv,
+							  DBUF_CTL_S2,
+							  slice_set);
+			break;
+		default:
+			MISSING_CASE(slice_bit);
+		}
+	}
 
 	if (ret)
 		dev_priv->wm.skl_hw.ddb.enabled_slices = req_slices;
@@ -4286,40 +4295,21 @@  void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 
 static void icl_dbuf_enable(struct drm_i915_private *dev_priv)
 {
-	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) | DBUF_POWER_REQUEST);
-	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) | DBUF_POWER_REQUEST);
-	POSTING_READ(DBUF_CTL_S2);
-
-	udelay(10);
-
-	if (!(I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
-	    !(I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
-		DRM_ERROR("DBuf power enable timeout\n");
-	else
-		/*
-		 * FIXME: for now pretend that we only have 1 slice, see
-		 * intel_enabled_dbuf_slices_num().
-		 */
-		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
+	/*
+	 * Just power up 1 slice, we will
+	 * figure out later which slices we have and what we need.
+	 */
+	dev_priv->wm.skl_hw.ddb.enabled_slices = DBUF_S1_BIT;
+	icl_dbuf_slices_restore(dev_priv);
 }
 
 static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
 {
-	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) & ~DBUF_POWER_REQUEST);
-	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) & ~DBUF_POWER_REQUEST);
-	POSTING_READ(DBUF_CTL_S2);
-
-	udelay(10);
-
-	if ((I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
-	    (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
-		DRM_ERROR("DBuf power disable timeout!\n");
-	else
-		/*
-		 * FIXME: for now pretend that the first slice is always
-		 * enabled, see intel_enabled_dbuf_slices_num().
-		 */
-		dev_priv->wm.skl_hw.ddb.enabled_slices = 1;
+	/*
+	 * Disable all slices
+	 */
+	dev_priv->wm.skl_hw.ddb.enabled_slices = 0;
+	icl_dbuf_slices_restore(dev_priv);
 }
 
 static void icl_mbus_init(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/display/intel_display_power.h b/drivers/gpu/drm/i915/display/intel_display_power.h
index 1da04f3e0fb3..c5afb3129571 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.h
+++ b/drivers/gpu/drm/i915/display/intel_display_power.h
@@ -311,8 +311,10 @@  intel_display_power_put_async(struct drm_i915_private *i915,
 	for ((wf) = intel_display_power_get((i915), (domain)); (wf); \
 	     intel_display_power_put_async((i915), (domain), (wf)), (wf) = 0)
 
+int intel_dbuf_max_slices(struct drm_i915_private *dev_priv);
 void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 			    u8 req_slices);
+void icl_dbuf_slices_restore(struct drm_i915_private *dev_priv);
 
 void chv_phy_powergate_lanes(struct intel_encoder *encoder,
 			     bool override, unsigned int mask);
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 82e4e6bf08c3..0307aec2c928 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -51,6 +51,7 @@ 
 #include "display/intel_bw.h"
 #include "display/intel_cdclk.h"
 #include "display/intel_display_types.h"
+#include "display/intel_display_power.h"
 #include "display/intel_dp.h"
 #include "display/intel_fbdev.h"
 #include "display/intel_hotplug.h"
@@ -2588,6 +2589,10 @@  static int intel_runtime_resume(struct device *kdev)
 	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
 		ret = vlv_resume_prepare(dev_priv, true);
 
+	/* Weird hack to fix ICL hardware bug, as it resets DBUF slices reg */
+	if (INTEL_GEN(dev_priv) == 11)
+		icl_dbuf_slices_restore(dev_priv);
+
 	intel_uncore_runtime_resume(&dev_priv->uncore);
 
 	intel_runtime_pm_enable_interrupts(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 7e0f67babe20..a396977c9c2d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -804,7 +804,7 @@  static inline bool skl_ddb_entry_equal(const struct skl_ddb_entry *e1,
 }
 
 struct skl_ddb_allocation {
-	u8 enabled_slices; /* GEN11 has configurable 2 slices */
+	u8 enabled_slices;   /* Bitmask of currently enabled DBuf slices */
 };
 
 struct skl_ddb_values {
diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index 1bb701d32a5d..39c3db4ef7da 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -614,7 +614,8 @@  static const struct intel_device_info intel_cherryview_info = {
 	.has_gt_uc = 1, \
 	.display.has_hdcp = 1, \
 	.display.has_ipc = 1, \
-	.ddb_size = 896
+	.ddb_size = 896, \
+	.supported_slices = 1
 
 #define SKL_PLATFORM \
 	GEN9_FEATURES, \
@@ -682,12 +683,14 @@  static const struct intel_device_info intel_broxton_info = {
 	GEN9_LP_FEATURES,
 	PLATFORM(INTEL_BROXTON),
 	.ddb_size = 512,
+	.supported_slices = 1,
 };
 
 static const struct intel_device_info intel_geminilake_info = {
 	GEN9_LP_FEATURES,
 	PLATFORM(INTEL_GEMINILAKE),
 	.ddb_size = 1024,
+	.supported_slices = 1,
 	GLK_COLORS,
 };
 
@@ -737,6 +740,7 @@  static const struct intel_device_info intel_coffeelake_gt3_info = {
 	GEN9_FEATURES, \
 	GEN(10), \
 	.ddb_size = 1024, \
+	.supported_slices = 1, \
 	.display.has_dsc = 1, \
 	.has_coherent_ggtt = false, \
 	GLK_COLORS
@@ -773,6 +777,7 @@  static const struct intel_device_info intel_cannonlake_info = {
 	}, \
 	GEN(11), \
 	.ddb_size = 2048, \
+	.supported_slices = 2, \
 	.has_logical_ring_elsq = 1, \
 	.color = { .degamma_lut_size = 33, .gamma_lut_size = 262145 }
 
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a607ea520829..fba5731063d8 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7734,9 +7734,11 @@  enum {
 #define DISP_ARB_CTL2	_MMIO(0x45004)
 #define  DISP_DATA_PARTITION_5_6	(1 << 6)
 #define  DISP_IPC_ENABLE		(1 << 3)
-#define DBUF_CTL	_MMIO(0x45008)
-#define DBUF_CTL_S1	_MMIO(0x45008)
-#define DBUF_CTL_S2	_MMIO(0x44FE8)
+#define DBUF_S1_BIT			BIT(0)
+#define DBUF_S2_BIT			BIT(1)
+#define DBUF_CTL			_MMIO(0x45008)
+#define DBUF_CTL_S1			_MMIO(0x45008)
+#define DBUF_CTL_S2			_MMIO(0x44FE8)
 #define  DBUF_POWER_REQUEST		(1 << 31)
 #define  DBUF_POWER_STATE		(1 << 30)
 #define GEN7_MSG_CTL	_MMIO(0x45010)
diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
index 4bdf8a6cfb47..ba34e1a5c591 100644
--- a/drivers/gpu/drm/i915/intel_device_info.h
+++ b/drivers/gpu/drm/i915/intel_device_info.h
@@ -180,6 +180,7 @@  struct intel_device_info {
 	} display;
 
 	u16 ddb_size; /* in blocks */
+	u8 supported_slices; /* number of DBuf slices */
 
 	/* Register offsets for the various display pipes and transcoders */
 	int pipe_offsets[I915_MAX_TRANSCODERS];
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2d389e437e87..b6627c845f1c 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3586,24 +3586,20 @@  bool ilk_disable_lp_wm(struct drm_device *dev)
 	return _ilk_disable_lp_wm(dev_priv, WM_DIRTY_LP_ALL);
 }
 
-static u8 intel_enabled_dbuf_slices_num(struct drm_i915_private *dev_priv)
+static u8 intel_enabled_dbuf_slices(struct drm_i915_private *dev_priv)
 {
-	u8 enabled_slices;
-
-	/* Slice 1 will always be enabled */
-	enabled_slices = 1;
+	u8 enabled_slices = 0;
 
 	/* Gen prior to GEN11 have only one DBuf slice */
 	if (INTEL_GEN(dev_priv) < 11)
-		return enabled_slices;
+		return DBUF_S1_BIT;
 
-	/*
-	 * FIXME: for now we'll only ever use 1 slice; pretend that we have
-	 * only that 1 slice enabled until we have a proper way for on-demand
-	 * toggling of the second slice.
-	 */
-	if (0 && I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
-		enabled_slices++;
+	/* Check if second DBuf slice is enabled */
+	if (I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE)
+		enabled_slices |= DBUF_S1_BIT;
+
+	if (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
+		enabled_slices |= DBUF_S2_BIT;
 
 	return enabled_slices;
 }
@@ -3812,36 +3808,38 @@  static u16 intel_get_ddb_size(struct drm_i915_private *dev_priv,
 			      const int num_active,
 			      struct skl_ddb_allocation *ddb)
 {
-	const struct drm_display_mode *adjusted_mode;
-	u64 total_data_bw;
 	u16 ddb_size = INTEL_INFO(dev_priv)->ddb_size;
-
 	WARN_ON(ddb_size == 0);
 
 	if (INTEL_GEN(dev_priv) < 11)
 		return ddb_size - 4; /* 4 blocks for bypass path allocation */
 
-	adjusted_mode = &crtc_state->hw.adjusted_mode;
-	total_data_bw = total_data_rate * drm_mode_vrefresh(adjusted_mode);
+	return ddb_size;
+}
 
-	/*
-	 * 12GB/s is maximum BW supported by single DBuf slice.
-	 *
-	 * FIXME dbuf slice code is broken:
-	 * - must wait for planes to stop using the slice before powering it off
-	 * - plane straddling both slices is illegal in multi-pipe scenarios
-	 * - should validate we stay within the hw bandwidth limits
-	 */
-	if (0 && (num_active > 1 || total_data_bw >= GBps(12))) {
-		ddb->enabled_slices = 2;
-	} else {
-		ddb->enabled_slices = 1;
-		ddb_size /= 2;
-	}
+/*
+ * Calculate initial DBuf slice offset, based on slice size
+ * and mask(i.e if slice size is 1024 and second slice is enabled
+ * offset would be 1024)
+ */
+static u32 skl_get_first_dbuf_slice_offset(u32 dbuf_slice_mask,
+					   u32 slice_size, u32 ddb_size)
+{
+	u32 offset = 0;
 
-	return ddb_size;
+	if (!dbuf_slice_mask)
+		return 0;
+
+	offset = (ffs(dbuf_slice_mask) - 1) * slice_size;
+
+	WARN_ON(offset >= ddb_size);
+	return offset;
 }
 
+static u32 i915_get_allowed_dbuf_mask(struct drm_i915_private *dev_priv,
+				      int pipe, u32 active_pipes,
+				      const struct intel_crtc_state *crtc_state);
+
 static void
 skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
 				   const struct intel_crtc_state *crtc_state,
@@ -3857,7 +3855,14 @@  skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
 	u32 pipe_width = 0, total_width = 0, width_before_pipe = 0;
 	enum pipe for_pipe = to_intel_crtc(for_crtc)->pipe;
 	u16 ddb_size;
+	u32 ddb_range_size;
 	u32 i;
+	u32 dbuf_slice_mask;
+	u32 active_pipes;
+	u32 offset;
+	u32 slice_size;
+	u32 total_slice_mask;
+	u32 start, end;
 
 	if (WARN_ON(!state) || !crtc_state->hw.active) {
 		alloc->start = 0;
@@ -3866,14 +3871,23 @@  skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
 		return;
 	}
 
-	if (intel_state->active_pipe_changes)
+	if (intel_state->active_pipe_changes) {
 		*num_active = hweight8(intel_state->active_pipes);
-	else
+		active_pipes = intel_state->active_pipes;
+	} else {
 		*num_active = hweight8(dev_priv->active_pipes);
+		active_pipes = dev_priv->active_pipes;
+	}
 
 	ddb_size = intel_get_ddb_size(dev_priv, crtc_state, total_data_rate,
 				      *num_active, ddb);
 
+	DRM_DEBUG_KMS("Got total ddb size %d\n", ddb_size);
+
+	slice_size = ddb_size / INTEL_INFO(dev_priv)->supported_slices;
+
+	DRM_DEBUG_KMS("Got DBuf slice size %d\n", slice_size);
+
 	/*
 	 * If the state doesn't change the active CRTC's or there is no
 	 * modeset request, then there's no need to recalculate;
@@ -3891,20 +3905,70 @@  skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
 		return;
 	}
 
+	/*
+	 * Get allowed DBuf slices for correspondent pipe and platform.
+	 */
+	dbuf_slice_mask = i915_get_allowed_dbuf_mask(dev_priv, for_pipe,
+						     active_pipes, crtc_state);
+
+	DRM_DEBUG_KMS("DBuf slice mask %x pipe %d active pipes %x\n",
+		      dbuf_slice_mask,
+		      for_pipe, active_pipes);
+
+	/*
+	 * Figure out at which DBuf slice we start, i.e if we start at Dbuf S2
+	 * and slice size is 1024, the offset would be 1024
+	 */
+	offset = skl_get_first_dbuf_slice_offset(dbuf_slice_mask,
+						 slice_size, ddb_size);
+
+	/*
+	 * Figure out total size of allowed DBuf slices, which is basically
+	 * a number of allowed slices for that pipe multiplied by slice size.
+	 * Inside of this
+	 * range ddb entries are still allocated in proportion to display width.
+	 */
+	ddb_range_size = hweight8(dbuf_slice_mask) * slice_size;
+
 	/*
 	 * Watermark/ddb requirement highly depends upon width of the
 	 * framebuffer, So instead of allocating DDB equally among pipes
 	 * distribute DDB based on resolution/width of the display.
 	 */
+	total_slice_mask = dbuf_slice_mask;
 	for_each_new_intel_crtc_in_state(intel_state, crtc, crtc_state, i) {
 		const struct drm_display_mode *adjusted_mode =
 			&crtc_state->hw.adjusted_mode;
 		enum pipe pipe = crtc->pipe;
 		int hdisplay, vdisplay;
+		u32 pipe_dbuf_slice_mask = \
+			i915_get_allowed_dbuf_mask(dev_priv,
+						pipe,
+						active_pipes,
+						crtc_state);
 
 		if (!crtc_state->hw.enable)
 			continue;
 
+		/*
+		 * According to BSpec pipe can share one dbuf slice with another
+		 * pipes or pipe can use multiple dbufs, in both cases we
+		 * account for other pipes only if they have exactly same mask.
+		 * However we need to account how many slices we should enable
+		 * in total.
+		 */
+		total_slice_mask |= pipe_dbuf_slice_mask;
+
+		/*
+		 * Do not account pipes using other slice sets
+		 * luckily as of current BSpec slice sets do not partially
+		 * intersect(pipes share either same one slice or same slice set
+		 * i.e no partial intersection), so it is enough to check for
+		 * equality for now.
+		 */
+		if (dbuf_slice_mask != pipe_dbuf_slice_mask)
+			continue;
+
 		drm_mode_get_hv_timing(adjusted_mode, &hdisplay, &vdisplay);
 		total_width += hdisplay;
 
@@ -3914,8 +3978,19 @@  skl_ddb_get_pipe_allocation_limits(struct drm_i915_private *dev_priv,
 			pipe_width = hdisplay;
 	}
 
-	alloc->start = ddb_size * width_before_pipe / total_width;
-	alloc->end = ddb_size * (width_before_pipe + pipe_width) / total_width;
+	ddb->enabled_slices = total_slice_mask;
+
+	start = ddb_range_size * width_before_pipe / total_width;
+	end = ddb_range_size * (width_before_pipe + pipe_width) / total_width;
+
+	alloc->start = offset + start;
+	alloc->end = offset + end;
+
+	DRM_DEBUG_KMS("Pipe %d ddb %d-%d\n", for_pipe,
+		      alloc->start, alloc->end);
+	DRM_DEBUG_KMS("Enabled ddb slices mask %x num supported %d\n",
+		      ddb->enabled_slices,
+		      INTEL_INFO(dev_priv)->supported_slices);
 }
 
 static int skl_compute_wm_params(const struct intel_crtc_state *crtc_state,
@@ -4036,7 +4111,8 @@  void skl_pipe_ddb_get_hw_state(struct intel_crtc *crtc,
 void skl_ddb_get_hw_state(struct drm_i915_private *dev_priv,
 			  struct skl_ddb_allocation *ddb /* out */)
 {
-	ddb->enabled_slices = intel_enabled_dbuf_slices_num(dev_priv);
+	ddb->enabled_slices = intel_enabled_dbuf_slices(dev_priv);
+	DRM_DEBUG_KMS("Got hw dbuf slices mask %x\n", ddb->enabled_slices);
 }
 
 /*
@@ -4164,6 +4240,238 @@  skl_get_total_relative_data_rate(struct intel_crtc_state *crtc_state,
 	return total_data_rate;
 }
 
+uint_fixed_16_16_t
+skl_pipe_downscale_amount(const struct intel_crtc_state *crtc_state)
+{
+	u32 src_w, src_h, dst_w, dst_h;
+	uint_fixed_16_16_t fp_w_ratio, fp_h_ratio;
+	uint_fixed_16_16_t downscale_h, downscale_w;
+	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+
+	src_w = crtc_state->pipe_src_w;
+	src_h = crtc_state->pipe_src_h;
+	dst_w = adjusted_mode->crtc_hdisplay;
+	dst_h = adjusted_mode->crtc_vdisplay;
+
+	fp_w_ratio = div_fixed16(src_w, dst_w);
+	fp_h_ratio = div_fixed16(src_h, dst_h);
+	downscale_w = max_fixed16(fp_w_ratio, u32_to_fixed16(1));
+	downscale_h = max_fixed16(fp_h_ratio, u32_to_fixed16(1));
+
+	return mul_fixed16(downscale_w, downscale_h);
+}
+
+uint_fixed_16_16_t
+icl_get_pipe_ratio(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_plane *plane;
+	const struct drm_plane_state *drm_plane_state;
+	uint_fixed_16_16_t pipe_downscale, pipe_ratio;
+	uint_fixed_16_16_t max_downscale = u32_to_fixed16(1);
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+
+	if (!crtc_state->uapi.enable)
+		return max_downscale;
+
+	drm_atomic_crtc_state_for_each_plane_state(plane, drm_plane_state, &crtc_state->uapi) {
+		uint_fixed_16_16_t plane_downscale;
+		const struct intel_plane_state *plane_state =
+			to_intel_plane_state(drm_plane_state);
+
+		if (!intel_wm_plane_visible(crtc_state, plane_state))
+			continue;
+
+		plane_downscale = skl_plane_downscale_amount(crtc_state, plane_state);
+
+		DRM_DEBUG_KMS("Plane %d downscale amount %d.%d\n",
+			      to_intel_plane(plane)->id,
+			      plane_downscale.val >> 16,
+			      plane_downscale.val & 0xffff);
+
+		max_downscale = max_fixed16(plane_downscale, max_downscale);
+	}
+
+
+	pipe_downscale = skl_pipe_downscale_amount(crtc_state);
+
+	DRM_DEBUG_KMS("Pipe %d downscale amount %d.%d\n",
+		       crtc->pipe, pipe_downscale.val >> 16,
+		       pipe_downscale.val & 0xffff);
+
+	pipe_downscale = mul_fixed16(pipe_downscale, max_downscale);
+
+	/* Convert result to percentage */
+	pipe_ratio = u32_to_fixed16(100 * div_round_up_u32_fixed16(1, pipe_downscale));
+
+	DRM_DEBUG_KMS("Pipe %d ratio %d.%d\n", crtc->pipe,
+		      pipe_ratio.val >> 16, pipe_ratio.val & 0xffff);
+
+	return pipe_ratio;
+}
+
+struct dbuf_slice_conf_entry {
+	u32 dbuf_mask[I915_MAX_PIPES];
+	u32 active_pipes;
+};
+
+
+#define ICL_PIPE_A_DBUF_SLICES(DBuf1)  \
+	{ { DBuf1, 0, 0, 0 }, BIT(PIPE_A) }
+#define ICL_PIPE_B_DBUF_SLICES(DBuf1)  \
+	{ { 0, DBuf1, 0, 0 }, BIT(PIPE_B) }
+#define ICL_PIPE_C_DBUF_SLICES(DBuf1)  \
+	{ { 0, 0, DBuf1, 0 }, BIT(PIPE_C) }
+#define ICL_PIPE_D_DBUF_SLICES(DBuf1)  \
+	{ { 0, 0, 0, DBuf1 }, BIT(PIPE_D) }
+#define ICL_PIPE_AB_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { DBuf1, DBuf2, 0, 0 }, BIT(PIPE_A) | BIT(PIPE_B) }
+#define ICL_PIPE_BC_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { 0, DBuf1, DBuf2, 0 }, BIT(PIPE_B) | BIT(PIPE_C) }
+#define ICL_PIPE_BD_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { 0, DBuf1, 0, DBuf2 }, BIT(PIPE_B) | BIT(PIPE_D) }
+#define ICL_PIPE_AC_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { DBuf1, 0, DBuf2, 0 }, BIT(PIPE_A) | BIT(PIPE_C) }
+#define ICL_PIPE_AD_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { DBuf1, 0, 0, DBuf2 }, BIT(PIPE_A) | BIT(PIPE_D) }
+#define ICL_PIPE_CD_DBUF_SLICES(DBuf1, DBuf2)   \
+	{ { 0, 0, DBuf1, DBuf2 }, BIT(PIPE_C) | BIT(PIPE_D) }
+#define ICL_PIPE_ABC_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
+	{ { DBuf1, DBuf2, DBuf3, 0 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_C) }
+#define ICL_PIPE_ACD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
+	{ { DBuf1, 0, DBuf2, DBuf3 }, BIT(PIPE_A) | BIT(PIPE_C) | BIT(PIPE_D) }
+#define ICL_PIPE_BCD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
+	{ { 0, DBuf1, DBuf2, DBuf3 }, BIT(PIPE_B) | BIT(PIPE_C) | BIT(PIPE_D) }
+#define ICL_PIPE_ABD_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
+	{ { DBuf1, DBuf2, 0, DBuf3 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_D) }
+#define ICL_PIPE_ABC_DBUF_SLICES(DBuf1, DBuf2, DBuf3)  \
+	{ { DBuf1, DBuf2, DBuf3, 0 }, BIT(PIPE_A) | BIT(PIPE_B) | BIT(PIPE_C) }
+#define ICL_PIPE_ABCD_DBUF_SLICES(DBuf1, DBuf2, DBuf3, DBuf4)  \
+	{ { DBuf1, DBuf2, DBuf3, DBuf4 }, BIT(PIPE_A) | BIT(PIPE_B) | \
+					  BIT(PIPE_C) | BIT(PIPE_D) }
+
+/*
+ * Table taken from Bspec 12716
+ * Pipes do have some preferred DBuf slice affinity,
+ * plus there are some hardcoded requirements on how
+ * those should be distributed for multipipe scenarios.
+ * For more DBuf slices algorithm can get even more messy
+ * and less readable, so decided to use a table almost
+ * as is from BSpec itself - that way it is at least easier
+ * to compare, change and check.
+ */
+struct dbuf_slice_conf_entry icl_allowed_dbufs[] = {
+{ { 0, 0, 0, 0 }, 0 },
+ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
+ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT),                /* for pipe ratio >= 88.8 */
+ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
+ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT),                /* for pipe ratio >= 88.8 */
+ICL_PIPE_C_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),  /* pipe ratio < 88.8 */
+ICL_PIPE_C_DBUF_SLICES(DBUF_S2_BIT),                /* for pipe ratio >= 88.8 */
+ICL_PIPE_AB_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_AC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_BC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_ABC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
+};
+
+/*
+ * Table taken from Bspec 49255
+ * Pipes do have some preferred DBuf slice affinity,
+ * plus there are some hardcoded requirements on how
+ * those should be distributed for multipipe scenarios.
+ * For more DBuf slices algorithm can get even more messy
+ * and less readable, so decided to use a table almost
+ * as is from BSpec itself - that way it is at least easier
+ * to compare, change and check.
+ */
+struct dbuf_slice_conf_entry tgl_allowed_dbufs[] = {
+{ { 0, 0, 0, 0 }, 0 },
+ICL_PIPE_A_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
+ICL_PIPE_B_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
+ICL_PIPE_C_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
+ICL_PIPE_D_DBUF_SLICES(DBUF_S1_BIT | DBUF_S2_BIT),
+ICL_PIPE_AB_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_AC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_BC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_AD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_BD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_CD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_ABD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_ABC_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT),
+ICL_PIPE_ACD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
+ICL_PIPE_BCD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
+ICL_PIPE_ABCD_DBUF_SLICES(DBUF_S1_BIT, DBUF_S1_BIT, DBUF_S2_BIT, DBUF_S2_BIT),
+};
+
+/*
+ * This function finds an entry with same enabled pipe configuration and
+ * returns correspondent DBuf slice mask as stated in BSpec for particular
+ * platform.
+ */
+static u32 icl_get_allowed_dbuf_mask(int pipe,
+				     u32 active_pipes,
+				     const struct intel_crtc_state *crtc_state)
+{
+	int i;
+	uint_fixed_16_16_t pipe_ratio;
+
+	/*
+	 * Calculate pipe ratio as stated in BSpec 28692
+	 */
+	pipe_ratio = icl_get_pipe_ratio(crtc_state);
+
+	for (i = 0; i < ARRAY_SIZE(icl_allowed_dbufs); i++) {
+		if (icl_allowed_dbufs[i].active_pipes == active_pipes) {
+			if (hweight32(active_pipes) == 1) {
+				/*
+				 * According to BSpec 12716: if ratio >= 88.8
+				 * always use single dbuf slice.
+				 */
+				if (pipe_ratio.val >= div_fixed16(888, 10).val)
+					++i;
+			}
+			return icl_allowed_dbufs[i].dbuf_mask[pipe];
+		}
+	}
+	return 0;
+}
+
+/*
+ * This function finds an entry with same enabled pipe configuration and
+ * returns correspondent DBuf slice mask as stated in BSpec for particular
+ * platform.
+ */
+static u32 tgl_get_allowed_dbuf_mask(int pipe,
+				     u32 active_pipes,
+				     const struct intel_crtc_state *crtc_state)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(tgl_allowed_dbufs); i++) {
+		if (tgl_allowed_dbufs[i].active_pipes == active_pipes)
+			return tgl_allowed_dbufs[i].dbuf_mask[pipe];
+	}
+	return 0;
+}
+
+u32 i915_get_allowed_dbuf_mask(struct drm_i915_private *dev_priv,
+				      int pipe, u32 active_pipes,
+				      const struct intel_crtc_state *crtc_state)
+{
+	if (IS_GEN(dev_priv, 11))
+		return icl_get_allowed_dbuf_mask(pipe,
+						 active_pipes,
+						 crtc_state);
+	else if (IS_GEN(dev_priv, 12))
+		return tgl_get_allowed_dbuf_mask(pipe,
+						 active_pipes,
+						 crtc_state);
+	/*
+	 * For anything else just return one slice yet.
+	 * Should be extended for other platforms.
+	 */
+	return DBUF_S1_BIT;
+}
+
 static u64
 icl_get_total_relative_data_rate(struct intel_crtc_state *crtc_state,
 				 u64 *plane_data_rate)