Re: [PATCH 15/20] drm/i915/dp: Read/ack sink count and sink IRQs for SST as it's done for MST

[Imre Deak <imre.deak@intel.com>]

On Thu, Jul 03, 2025 at 04:02:18PM +0300, Luca Coelho wrote:
> On Thu, 2025-06-26 at 11:20 +0300, Imre Deak wrote:
> > From: Imre Deak <imre.deak@gmail.com>
> > 
> > Read and ack the sink count, sink device and link service IRQs for SST
> > the same way this is done for MST, the read/ack happening in separate
> > steps via an ESI (Event Status Indicator) vector.
> > 
> > The above way is more efficient, since on newer (DPCD_REV >= 1.2) sinks
> > the DP_SINK_COUNT_ESI..DP_LINK_SERVICE_IRQ_VECTOR_ESI0 registers can be
> > read out in one AUX transaction - and the 3 last one written in one
> > transaction. Also this allows sharing more of the SST and MST IRQ
> > handling code (done as a follow-up).
> > 
> > For now keep the current behavior of always reading the legacy
> > DP_SINK_COUNT, DP_DEVICE_SERVICE_IRQ_VECTOR registers and not reading
> > the DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1 register.
> > 
> > Signed-off-by: Imre Deak <imre.deak@gmail.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 132 +++++++++++++-----------
> >  1 file changed, 73 insertions(+), 59 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 2ba4a810f22c2..2e6ed7d2a64a6 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -4573,6 +4573,70 @@ static bool intel_dp_ack_sink_irq_esi(struct intel_dp *intel_dp, u8 esi[4])
> >  	return false;
> >  }
> >  
> > +static bool intel_dp_get_sink_irq_esi_sst(struct intel_dp *intel_dp, u8 esi[4])
> > +{
> > +	memset(esi, 0, 4);
> > +
> > +	/*
> > +	 * TODO: For DP_DPCD_REV >= 0x12 read
> > +	 * DP_SINK_COUNT_ESI and DP_DEVICE_SERVICE_IRQ_VECTOR_ESI0.
> > +	 */
> > +	if (drm_dp_dpcd_read_data(&intel_dp->aux, DP_SINK_COUNT, esi, 2) != 0)
> > +		return false;
> > +
> > +	if (intel_dp->dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
> > +		return true;
> > +
> > +	/* TODO: Read DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1 as well */
> > +	if (drm_dp_dpcd_read_byte(&intel_dp->aux, DP_LINK_SERVICE_IRQ_VECTOR_ESI0, &esi[3]) != 0)
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> > +static bool intel_dp_ack_sink_irq_esi_sst(struct intel_dp *intel_dp, u8 esi[4])
> > +{
> > +	/*
> > +	 * TODO: For DP_DPCD_REV >= 0x12 write
> > +	 * DP_DEVICE_SERVICE_IRQ_VECTOR_ESI0
> > +	 */
> > +	if (drm_dp_dpcd_write_byte(&intel_dp->aux, DP_DEVICE_SERVICE_IRQ_VECTOR, esi[1]) != 0)
> > +		return false;
> > +
> > +	if (intel_dp->dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
> > +		return true;
> > +
> > +	/* TODO: Read DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1 as well */
> > +	if (drm_dp_dpcd_write_byte(&intel_dp->aux, DP_LINK_SERVICE_IRQ_VECTOR_ESI0, esi[3]) != 0)
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> > +static bool intel_dp_get_and_ack_sink_irq_esi_sst(struct intel_dp *intel_dp, u8 esi[4])
> > +{
> > +	struct intel_display *display = to_intel_display(intel_dp);
> > +	struct intel_connector *connector = intel_dp->attached_connector;
> > +	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
> > +
> > +	if (!intel_dp_get_sink_irq_esi_sst(intel_dp, esi))
> > +		return false;
> > +
> > +	drm_dbg_kms(display->drm,
> > +		    "[CONNECTOR:%d:%s][ENCODER:%d:%s] DPRX ESI: %4ph\n",
> > +		    connector->base.base.id, connector->base.name,
> > +		    encoder->base.base.id, encoder->base.name,
> > +		    esi);
> > +
> > +	if (mem_is_zero(&esi[1], 3))
> > +		return true;
> > +
> > +	if (!intel_dp_ack_sink_irq_esi_sst(intel_dp, esi))
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> 
> Again, I think it's better to propagate the error than to swallow it
> and return a bool.

I agree. But doing that would make these functions return error in
different ways than the MST

intel_dp_get_sink_irq_esi(), intel_dp_ack_sink_irq_esi()

functions, which return a pass/fail bool. Imo the error return should be
the same for both the SST and MST variety of functions and converting
to propagate an error instead of a pass/fail bool should be done for
both (SST and MST), which is best done as a follow-up. Are you ok with
that?

> Other than that, it looks good to me.  So if you agree with this
> change:
>
> Reviewed-by: Luca Coelho <luciano.coelho@tintel.com>
> 
> --
> Cheers,
> Luca.
> 
> > @@ -5393,27 +5457,6 @@ void intel_dp_check_link_state(struct intel_dp *intel_dp)
> >  	intel_encoder_link_check_queue_work(encoder, 0);
> >  }
> >  
> > -static bool intel_dp_get_and_ack_device_service_irq(struct intel_dp *intel_dp, u8 *irq_mask)
> > -{
> > -	u8 val;
> > -
> > -	*irq_mask = 0;
> > -
> > -	if (drm_dp_dpcd_readb(&intel_dp->aux,
> > -			      DP_DEVICE_SERVICE_IRQ_VECTOR, &val) != 1)
> > -		return false;
> > -
> > -	if (!val)
> > -		return true;
> > -
> > -	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_DEVICE_SERVICE_IRQ_VECTOR, val) != 1)
> > -		return false;
> > -
> > -	*irq_mask = val;
> > -
> > -	return true;
> > -}
> > -
> >  static void intel_dp_handle_device_service_irq(struct intel_dp *intel_dp, u8 irq_mask)
> >  {
> >  	struct intel_display *display = to_intel_display(intel_dp);
> > @@ -5428,31 +5471,6 @@ static void intel_dp_handle_device_service_irq(struct intel_dp *intel_dp, u8 irq
> >  		drm_dbg_kms(display->drm, "Sink specific irq unhandled\n");
> >  }
> >  
> > -static bool intel_dp_get_and_ack_link_service_irq(struct intel_dp *intel_dp, u8 *irq_mask)
> > -{
> > -	u8 val;
> > -
> > -	*irq_mask = 0;
> > -
> > -	if (intel_dp->dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
> > -		return true;
> > -
> > -	if (drm_dp_dpcd_readb(&intel_dp->aux,
> > -			      DP_LINK_SERVICE_IRQ_VECTOR_ESI0, &val) != 1)
> > -		return false;
> > -
> > -	if (!val)
> > -		return true;
> > -
> > -	if (drm_dp_dpcd_writeb(&intel_dp->aux,
> > -			       DP_LINK_SERVICE_IRQ_VECTOR_ESI0, val) != 1)
> > -		return false;
> > -
> > -	*irq_mask = val;
> > -
> > -	return true;
> > -}
> > -
> >  static bool intel_dp_handle_link_service_irq(struct intel_dp *intel_dp, u8 irq_mask)
> >  {
> >  	struct intel_display *display = to_intel_display(intel_dp);
> > @@ -5489,30 +5507,26 @@ static bool
> >  intel_dp_short_pulse(struct intel_dp *intel_dp)
> >  {
> >  	bool reprobe_needed = false;
> > -	u8 irq_mask;
> > +	u8 esi[4] = {};
> >  
> >  	intel_dp_test_reset(intel_dp);
> >  
> > +	if (!intel_dp_get_and_ack_sink_irq_esi_sst(intel_dp, esi))
> > +		return false;
> > +
> >  	/*
> > -	 * Now read the DPCD to see if it's actually running
> >  	 * If the current value of sink count doesn't match with
> > -	 * the value that was stored earlier or dpcd read failed
> > -	 * we need to do full detection
> > +	 * the value that was stored earlier we need to do full
> > +	 * detection.
> >  	 */
> >  	if (intel_dp_has_sink_count(intel_dp) &&
> > -	    drm_dp_read_sink_count(&intel_dp->aux) != intel_dp->sink_count)
> > +	    DP_GET_SINK_COUNT(esi[0]) != intel_dp->sink_count)
> >  		/* No need to proceed if we are going to do full detect */
> >  		return false;
> >  
> > -	if (!intel_dp_get_and_ack_device_service_irq(intel_dp, &irq_mask))
> > -		return false;
> > +	intel_dp_handle_device_service_irq(intel_dp, esi[1]);
> >  
> > -	intel_dp_handle_device_service_irq(intel_dp, irq_mask);
> > -
> > -	if (!intel_dp_get_and_ack_link_service_irq(intel_dp, &irq_mask))
> > -		return false;
> > -
> > -	if (intel_dp_handle_link_service_irq(intel_dp, irq_mask))
> > +	if (intel_dp_handle_link_service_irq(intel_dp, esi[3]))
> >  		reprobe_needed = true;
> >  
> >  	/* Handle CEC interrupts, if any */