Re: [PATCH 08/19] drm/i915/display: Add DC3CO eligibility computation

[Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>]

On 14-04-2026 03:12, Shankar, Uma wrote:
>
>> -----Original Message-----
>> From: Dibin Moolakadan Subrahmanian
>> <dibin.moolakadan.subrahmanian@intel.com>
>> Sent: Thursday, March 26, 2026 10:46 PM
>> To: intel-gfx@lists.freedesktop.org; intel-xe@lists.freedesktop.org
>> Cc: Manna, Animesh <animesh.manna@intel.com>; Shankar, Uma
>> <uma.shankar@intel.com>; Kurmi, Suresh Kumar
>> <suresh.kumar.kurmi@intel.com>
>> Subject: [PATCH 08/19] drm/i915/display: Add DC3CO eligibility computation
>>
>> Compute DC3CO eligibility during atomic_check based on pipe/port constraints
>> and runtime triggers, and propagate the result via intel_atomic_state.
>>
>> 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 .
> Specify reasoning for reducing delay, would be good to add as comment.

I will add reason as comment

>> BSpec: 75253
>> Signed-off-by: Dibin Moolakadan Subrahmanian
>> <dibin.moolakadan.subrahmanian@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_display.c  | 98 ++++++++++++++++++-
>> drivers/gpu/drm/i915/display/intel_display.h  |  2 +-
>>   .../drm/i915/display/intel_display_types.h    |  7 ++
>>   3 files changed, 101 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
>> b/drivers/gpu/drm/i915/display/intel_display.c
>> index f20d5ebe06ed..df0eaf6ae76b 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> @@ -5943,6 +5943,81 @@ static bool intel_pipes_need_modeset(struct
>> intel_atomic_state *state,
>>   	return false;
>>   }
>>
>> +bool intel_dc3co_allowed(struct intel_atomic_state *state) {
>> +	return state && state->dc3co.allowed;
>> +}
>> +
>> +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);
>> +
>> +	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;
>> +	int active_pipes = 0;
>> +	u32 trigger = 0;
>> +
>> +	/* disable unless all conditions are met */
>> +	state->dc3co.trigger = DC3CO_TRIGGER_NONE;
>> +	state->dc3co.allowed = false;
>> +
>> +	if (!HAS_DC3CO(display))
>> +		return;
>> +
>> +	if (state->modeset)
>> +		return;
>> +
>> +	for_each_intel_crtc(display->drm, crtc) {
>> +		crtc_state = intel_atomic_get_new_crtc_state(state, crtc);
>> +		if (!crtc_state)
>> +			crtc_state = intel_atomic_get_old_crtc_state(state, crtc);
>> +
>> +		if (!crtc_state || !crtc_state->hw.active)
>> +			continue;
>> +
>> +		active_pipes++;
>> +
>> +		if (active_pipes > 1)
>> +			return;
>> +
>> +		for_each_intel_encoder_mask(display->drm, encoder,
>> +					    crtc_state->uapi.encoder_mask) {
>> +			if (encoder->type != INTEL_OUTPUT_EDP)
>> +				return;
>> +
>> +			intel_dp = enc_to_intel_dp(encoder);
>> +
>> +			if (!intel_dc3co_port_pipe_compatible(intel_dp,
>> crtc_state))
>> +				return;
>> +		}
>> +
>> +		if (crtc_state->has_lobf)
>> +			trigger |= DC3CO_TRIGGER_LOBF;
>> +		if (crtc_state->has_panel_replay)
>> +			trigger |= DC3CO_TRIGGER_PANEL_REPLAY;
>> +		if (crtc_state->has_sel_update)
>> +			trigger |= DC3CO_TRIGGER_PSR2;
>> +	}
> Leave a blank line

will fix this.

>
>> +	if (trigger) {
>> +		state->dc3co.trigger = trigger;
> Here if we have 2 pipes, trigger will still get updated. Harmless but it doesn't look nice.
> Would be good to fix it to reflect default value for trigger if more than 1 crtc's.

when two pipes are active control wont reach here, It will return from
for loop itself.

>> +		state->dc3co.allowed = true;
>> +	}
> Here as well.
>
>> +	drm_dbg_kms(display->drm, "DC3CO allowed=%d trigger=0x%x\n",
>> +		    state->dc3co.allowed, state->dc3co.trigger); }
>> +
>>   static int intel_atomic_check_joiner(struct intel_atomic_state *state,
>>   				     struct intel_crtc *primary_crtc)  { @@ -6623,6
>> +6698,7 @@ int intel_atomic_check(struct drm_device *dev,
>>   	if (ret)
>>   		goto fail;
>>
>> +	intel_dc3co_compute_state(state);
>>   	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
>>   					    new_crtc_state, i) {
>>   		intel_color_assert_luts(new_crtc_state);
>> @@ -7505,6 +7581,7 @@ 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;
>> +	int power_async_delay;
>>
>>   	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i)
>>   		intel_atomic_dsb_prepare(state, crtc); @@ -7711,11 +7788,22
>> @@ 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_dc3co_allowed(state) &&
>> +	    intel_display_power_dc3co_supported(display)) {
>> +		intel_display_power_set_target_dc_state(display,
>> DC_STATE_EN_UPTO_DC3CO);
>> +		power_async_delay = 1;
> Add comment explaining reason for 1ms delay.

I will add comment.

> What happens if DC3Co was already enabled. Do we need to enable again at every commit ?

DC state is disabled in the beginning of this function, so it looks okay to re enable here.

>
>> +	} else {
>> +		/*
>> +		 * Delay re-enabling DC states by 17 ms to avoid the off->on->off
>> +		 * toggling overhead at and above 60 FPS.
>> +		 */
>> +		intel_display_power_set_target_dc_state(display,
>> DC_STATE_EN_UPTO_DC6);
>> +		power_async_delay = 17;
>> +	}
> Leave a blank line.
>
>> +	intel_display_power_put_async_delay(display,
>> +					    POWER_DOMAIN_DC_OFF, wakeref,
>> power_async_delay);
>> +
>>   	intel_display_rpm_put(display, state->wakeref);
>>
>>   	/*
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.h
>> b/drivers/gpu/drm/i915/display/intel_display.h
>> index 552a59d19e0f..6eb84f9d8791 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display.h
>> @@ -535,5 +535,5 @@ bool assert_port_valid(struct intel_display *display, enum
>> port port);
>>
>>   bool intel_scanout_needs_vtd_wa(struct intel_display *display);  int
>> intel_crtc_num_joined_pipes(const struct intel_crtc_state *crtc_state);
>> -
>> +bool intel_dc3co_allowed(struct intel_atomic_state *state);
>>   #endif
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
>> b/drivers/gpu/drm/i915/display/intel_display_types.h
>> index 6830f911d94d..6c7f5bbbc821 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -632,6 +632,11 @@ struct dpll {
>>   	int	p;
>>   };
>>
>> +struct intel_dc3co_state {
>> +	bool allowed; /* DC3CO eligibility result */
>> +	u32 trigger; /* Bitmask of active DC3CO triggers */ };
>> +
>>   struct intel_atomic_state {
>>   	struct drm_atomic_state base;
>>
>> @@ -658,6 +663,8 @@ struct intel_atomic_state {
>>   	bool rps_interactive;
>>
>>   	struct work_struct cleanup_work;
>> +
>> +	struct intel_dc3co_state dc3co;
> Atomic_state may not be the right place for this, check and place it at right structure.

I will dc3co from atomic state.

>
>>   };
>>
>>   struct intel_plane_state {
>> --
>> 2.43.0