Re: [PATCH v4 07/13] drm/i915/display: Add DC3CO eligibility computation

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 27 May 2026, Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com> wrote:
> Compute DC3CO eligibility during atomic_check based on
> pipe/port constraints and runtime triggers and store
> result in display->power.dc3co.

Atomic check should not change persistent state. It's almost always a
mistake. (I guess sometimes can't be avoided.)

> When DC3CO is allowed, request DC_STATE_EN_UPTO_DC3CO and
> reduce the DC entry delay. Otherwise, retain the existing
> delay and set default DC_STATE_EN_UPTO_DC6.
>
> Changes in v2:
> - Move dc3co state from intel_atomic_state to display->power (Uma Shankar)
> - Use #define bitmasks instead of enum for DC3CO triggers (Jani Nikula)
>
> Changes in v3:
> - Fix trigger always returning zero in intel_dc3co_compute_state().
>
> Changes in v4:
> - Call intel_display_power_set_target_dc_state() only when DC3CO is
>   supported.
> - For Panel replay DC3CO trigger, add check for as_sdp_supported flag
> - Add 1:1 mapping check to intel_dc3co_port_pipe_compatible for
>   display version 35.(Uma Shankar,Animesh Manna)
> - Add guard for intel_dc3co_compute_state()
>
> BSpec: 75253
> Signed-off-by: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c  | 102 +++++++++++++++++-
>  .../gpu/drm/i915/display/intel_display_core.h |   3 +-
>  .../drm/i915/display/intel_display_power.c    |  30 ++++++
>  .../drm/i915/display/intel_display_power.h    |  22 ++++
>  4 files changed, 151 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 757a78c75bbf..375ffb329022 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -5874,6 +5874,74 @@ static bool intel_pipes_need_modeset(struct intel_atomic_state *state,
>  	return false;
>  }
>  
> +static bool intel_dc3co_port_pipe_compatible(struct intel_dp *intel_dp,
> +					     const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> +	enum pipe pipe = to_intel_crtc(crtc_state->uapi.crtc)->pipe;
> +	enum port port = dig_port->base.port;
> +	int num_pipes = intel_crtc_num_joined_pipes(crtc_state);
> +
> +	/* Need to follow 1:1 mapping because of CMTG restriction*/
> +	if (DISPLAY_VER(to_intel_display(crtc_state)) == 35)
> +		return num_pipes == 1 &&
> +		       ((pipe == PIPE_A && port == PORT_A) ||
> +			(pipe == PIPE_B && port == PORT_B));
> +	else
> +		return num_pipes == 1 && pipe <= PIPE_B && port <= PORT_B;
> +}
> +
> +static void intel_dc3co_compute_state(struct intel_atomic_state *state)
> +{
> +	struct intel_display *display = to_intel_display(state);
> +	struct intel_crtc *crtc;
> +	struct intel_crtc_state *crtc_state;
> +	struct intel_encoder *encoder;
> +	struct intel_dp *intel_dp;
> +	u8 active_pipes = 0;
> +	enum pipe pipe;
> +	u32 trigger = DC3CO_TRIGGER_NONE;
> +
> +	if (!HAS_DC3CO(display))
> +		return;
> +
> +	for_each_intel_crtc(display->drm, crtc)
> +		active_pipes |= crtc->active ? BIT(crtc->pipe) : 0;
> +
> +	active_pipes = intel_calc_active_pipes(state, active_pipes);
> +
> +	if (hweight8(active_pipes) != 1)
> +		goto done;
> +
> +	pipe = ffs(active_pipes) - 1;
> +	crtc = intel_crtc_for_pipe(display, pipe);
> +
> +	crtc_state = to_intel_crtc_state(crtc->base.state);
> +
> +	for_each_intel_encoder_mask(display->drm, encoder,
> +				    crtc_state->uapi.encoder_mask) {
> +		if (encoder->type != INTEL_OUTPUT_EDP)
> +			goto done;
> +
> +		intel_dp = enc_to_intel_dp(encoder);
> +
> +		if (!intel_dc3co_port_pipe_compatible(intel_dp, crtc_state))
> +			goto done;
> +	}
> +
> +	if (crtc_state->has_lobf)
> +		trigger |= DC3CO_TRIGGER_LOBF;
> +	if (crtc_state->has_panel_replay && intel_dp->as_sdp_supported)
> +		trigger |= DC3CO_TRIGGER_PANEL_REPLAY;
> +	if (crtc_state->has_sel_update)
> +		trigger |= DC3CO_TRIGGER_PSR2;
> +
> +done:
> +	intel_display_power_dc3co_update(display, !!trigger, trigger);

Are two parameters necessary?

> +	drm_dbg_kms(display->drm, "DC3CO allowed=%d trigger=0x%x\n",
> +		    !!trigger, trigger);
> +}

None of the above stuff belongs in intel_display.c. The file's too big
as it is. Probably intel_display_power.c.

> +
>  static int intel_atomic_check_joiner(struct intel_atomic_state *state,
>  				     struct intel_crtc *primary_crtc)
>  {
> @@ -6570,6 +6638,9 @@ int intel_atomic_check(struct drm_device *dev,
>  				      "modeset" : "fastset");
>  	}
>  
> +	if (intel_display_power_dc3co_supported(display))
> +		intel_dc3co_compute_state(state);
> +

Smells like intel_display_power_atomic_check(), maybe, without the if
statement here.

>  	return 0;
>  
>   fail:
> @@ -7421,6 +7492,12 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  	struct intel_power_domain_mask put_domains[I915_MAX_PIPES] = {};
>  	struct ref_tracker *wakeref = NULL;
>  	int i;
> +	u32 target_dc_state;
> +	/*
> +	 * Delay re-enabling DC states by 17 ms to avoid the off->on->off
> +	 * toggling overhead at and above 60 FPS.
> +	 */
> +	int power_async_delay = 17;
>  
>  	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i)
>  		intel_atomic_dsb_prepare(state, crtc);
> @@ -7627,11 +7704,26 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  		 */
>  		intel_uncore_arm_unclaimed_mmio_detection(uncore);
>  	}
> -	/*
> -	 * Delay re-enabling DC states by 17 ms to avoid the off->on->off
> -	 * toggling overhead at and above 60 FPS.
> -	 */
> -	intel_display_power_put_async_delay(display, POWER_DOMAIN_DC_OFF, wakeref, 17);
> +
> +	if (intel_display_power_dc3co_supported(display)) {
> +		if (intel_display_power_dc3co_allowed(display)) {
> +			/*
> +			 * Use minimal re-enable delay to allow DC3CO entry on
> +			 * the next idle frame, unlike the 17ms guard needed to
> +			 * prevent DC5/DC6 toggling overhead at 60+ FPS.
> +			 */
> +			power_async_delay = 1;
> +			target_dc_state = DC_STATE_EN_UPTO_DC3CO;
> +		} else {
> +			target_dc_state = DC_STATE_EN_UPTO_DC6;
> +		}
> +
> +		intel_display_power_set_target_dc_state(display, target_dc_state);
> +	}
> +

This is also way too detailed for intel_atomic_commit_tail(). This is
the highest level of modeset functions. See the code around here,
there's nothing as detailed.

> +	intel_display_power_put_async_delay(display,
> +					    POWER_DOMAIN_DC_OFF, wakeref, power_async_delay);

Maybe need to consider intel_display_power_put_commit_tail() or
something along those lines to hide all of the delay stuff there.


> +
>  	intel_display_rpm_put(display, state->wakeref);
>  
>  	/*
> diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
> index 3dc5ac75a98b..e24accf473d7 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_core.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_core.h
> @@ -537,7 +537,8 @@ struct intel_display {
>  
>  	struct {
>  		struct i915_power_domains domains;
> -
> +		/* DC3CO eligibility state */
> +		struct intel_dc3co_state dc3co;
>  		/* Shadow for DISPLAY_PHY_CONTROL which can't be safely read */
>  		u32 chv_phy_control;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
> index 4b91747b38f1..b0f40e4233c8 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.c
> @@ -366,6 +366,35 @@ bool intel_display_power_dc3co_supported(struct intel_display *display)
>  	return (power_domains->allowed_dc_mask & DC_STATE_EN_UPTO_DC3CO) == DC_STATE_EN_UPTO_DC3CO;
>  }
>  
> +void intel_display_power_dc3co_update(struct intel_display *display,
> +				      bool allowed, u32 trigger)
> +{
> +	struct intel_dc3co_state *dc3co = &display->power.dc3co;
> +
> +	if (!HAS_DC3CO(display))
> +		return;
> +
> +	mutex_lock(&dc3co->lock);
> +	dc3co->allowed = allowed;

Can this always be derived from dc3co->trigger?

> +	dc3co->trigger = trigger;
> +	mutex_unlock(&dc3co->lock);
> +}
> +
> +bool intel_display_power_dc3co_allowed(struct intel_display *display)
> +{
> +	struct intel_dc3co_state *dc3co = &display->power.dc3co;
> +	bool allowed;
> +
> +	if (!HAS_DC3CO(display))
> +		return false;
> +
> +	mutex_lock(&dc3co->lock);
> +	allowed = dc3co->allowed;
> +	mutex_unlock(&dc3co->lock);
> +
> +	return allowed;
> +}
> +
>  static void __async_put_domains_mask(struct i915_power_domains *power_domains,
>  				     struct intel_power_domain_mask *mask)
>  {
> @@ -1045,6 +1074,7 @@ int intel_power_domains_init(struct intel_display *display)
>  		sanitize_target_dc_state(display, DC_STATE_EN_UPTO_DC6);
>  
>  	mutex_init(&power_domains->lock);
> +	mutex_init(&display->power.dc3co.lock);
>  
>  	INIT_DELAYED_WORK(&power_domains->async_put_work,
>  			  intel_display_power_put_async_work);
> diff --git a/drivers/gpu/drm/i915/display/intel_display_power.h b/drivers/gpu/drm/i915/display/intel_display_power.h
> index 05880e9da89f..0b1a06f88ae5 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.h
> @@ -131,6 +131,25 @@ struct intel_power_domain_mask {
>  	DECLARE_BITMAP(bits, POWER_DOMAIN_NUM);
>  };
>  
> +/*
> + * DC3CO enabling triggers (bitmask).
> + * DC3CO may be enabled when at least one of these triggers is active.
> + * Additional constraints may still apply.
> + */
> +#define DC3CO_TRIGGER_NONE		(0)
> +#define DC3CO_TRIGGER_PSR2		BIT(0)
> +#define DC3CO_TRIGGER_LOBF		BIT(1)
> +#define DC3CO_TRIGGER_PANEL_REPLAY	BIT(2)
> +#define DC3CO_TRIGGER_ALL		(DC3CO_TRIGGER_PSR2 | \
> +					 DC3CO_TRIGGER_LOBF | \
> +					 DC3CO_TRIGGER_PANEL_REPLAY)
> +
> +struct intel_dc3co_state {
> +	struct mutex lock; /* Protects allowed and trigger fields */
> +	bool allowed; /* DC3CO eligibility result */
> +	u32 trigger; /* Bitmask of active DC3CO triggers */
> +};
> +
>  struct i915_power_domains {
>  	/*
>  	 * Power wells needed for initialization at driver init and suspend
> @@ -187,6 +206,9 @@ void intel_display_power_set_target_dc_state(struct intel_display *display,
>  					     u32 state);
>  u32 intel_display_power_get_current_dc_state(struct intel_display *display);
>  bool intel_display_power_dc3co_supported(struct intel_display *display);
> +void intel_display_power_dc3co_update(struct intel_display *display,
> +				      bool allowed, u32 trigger);
> +bool intel_display_power_dc3co_allowed(struct intel_display *display);
>  
>  bool intel_display_power_is_enabled(struct intel_display *display,
>  				    enum intel_display_power_domain domain);

-- 
Jani Nikula, Intel