[PATCH 19/20] drm/i915/dp: Ack only the handled device service IRQs

[Luca Coelho]

On Thu, 2025-06-26 at 11:20 +0300, Imre Deak wrote:
> From: Imre Deak <imre.deak at gmail.com>
> 
> Only those IRQs should be acked that are handled, however for SST all
> IRQs triggered by the sink are acked. This can be a problem for flags
> that are reserved/reading zero at a given moment, but become used for
> some purpose - with a side-effect if set - in a future DPCD revision.
> 
> Fix the above by acking only those device service IRQs that will be
> handled. While at it add asserts that only the known/acked device
> service IRQs are handled both in the MST and SST case.
> 
> Signed-off-by: Imre Deak <imre.deak at gmail.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 52249fa5c8a6d..6f67fac9724e1 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4537,6 +4537,14 @@ intel_dp_mst_disconnect(struct intel_dp *intel_dp)
>  	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst.mgr, intel_dp->is_mst);
>  }
>  
> +#define INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST	(DP_AUTOMATED_TEST_REQUEST | \
> +						 DP_CP_IRQ | \
> +						 DP_SINK_SPECIFIC_IRQ)
> +
> +#define INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST	(DP_CP_IRQ | \
> +						 DP_DOWN_REP_MSG_RDY | \
> +						 DP_UP_REQ_MSG_RDY)
> +
>  static bool
>  intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *esi)
>  {
> @@ -4628,6 +4636,8 @@ static bool intel_dp_get_and_ack_sink_irq_esi_sst(struct intel_dp *intel_dp, u8
>  		    encoder->base.base.id, encoder->base.name,
>  		    esi);
>  
> +	esi[1] &= INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST;
> +
>  	if (mem_is_zero(&esi[1], 3))
>  		return true;
>  
> @@ -5172,6 +5182,8 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  		if (mem_is_zero(ack, sizeof(ack)))
>  			break;
>  
> +		drm_WARN_ON(display->drm, ack[1] & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST);
> +
>  		if (!intel_dp_ack_sink_irq_esi(intel_dp, ack))
>  			drm_dbg_kms(display->drm, "Failed to ack ESI\n");
>  
> @@ -5456,6 +5468,8 @@ static void intel_dp_handle_device_service_irq(struct intel_dp *intel_dp, u8 irq
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  
> +	drm_WARN_ON(display->drm, irq_mask & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_SST);
> +
>  	if (irq_mask & DP_AUTOMATED_TEST_REQUEST)
>  		intel_dp_test_request(intel_dp);
>  

Evidently, this function is specific to SST irq.  Wouldn't it be better
to have _sst in the name like in "intel_dp_check_mst_status()"? This
function is probably in an earlier patch, though, so if handled it
should be obviously be done there.

Otherwise:

Reviewed-by: Luca Coelho <luciano.coelho at intel.com>

--
Cheers,
Luca.