On Tue, 2025-07-01 at 11:32 +0300, Imre Deak wrote: > On Tue, Jul 01, 2025 at 11:02:30AM +0300, Luca Coelho wrote: > > On Thu, 2025-06-26 at 11:20 +0300, Imre Deak wrote: > > > From: Imre Deak <imre.d...@gmail.com> > > > > > > HPD IRQs in general should be handled after acking them. The > > > > > > 1. Read IRQ register (read DP_DEVICE_SERVICE_IRQ_VECTOR, > > > DP_LINK_SERVICE_IRQ_VECTOR_ESI0) > > > 2. Handle IRQ > > > 3. Ack IRQ (write DP_DEVICE_SERVICE_IRQ_VECTOR, > > > DP_LINK_SERVICE_IRQ_VECTOR_ESI0) > > > > > > sequence would miss a new interrupt triggered after 2. and before 3., > > > since the flag set in the IRQ register for this interrupt would be > > > cleared in step 3. > > > > > > Fix the above by handling the IRQ after acking it. > > > > > > Signed-off-by: Imre Deak <imre.d...@gmail.com> > > > --- > > > drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++-------------- > > > 1 file changed, 11 insertions(+), 14 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c > > > b/drivers/gpu/drm/i915/display/intel_dp.c > > > index 285cd9a5d4a7b..453416b9e9bec 100644 > > > --- a/drivers/gpu/drm/i915/display/intel_dp.c > > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > > > @@ -5099,17 +5099,10 @@ intel_dp_check_mst_status(struct intel_dp > > > *intel_dp) > > > > > > drm_dbg_kms(display->drm, "DPRX ESI: %4ph\n", esi); > > > > > > - ack[3] |= esi[3] & LINK_STATUS_CHANGED; > > > + ack[3] |= esi[3] & (LINK_STATUS_CHANGED | DP_TUNNELING_IRQ); > > > > > > intel_dp_mst_hpd_irq(intel_dp, esi, ack); > > > > > > - if (esi[3] & DP_TUNNELING_IRQ) { > > > - if (drm_dp_tunnel_handle_irq(display->dp_tunnel_mgr, > > > - &intel_dp->aux)) > > > - reprobe_needed = true; > > > - ack[3] |= DP_TUNNELING_IRQ; > > > - } > > > - > > > if (mem_is_zero(ack, sizeof(ack))) > > > break; > > > > What happens if we ack the interrupt, but end up not handling it, e.g. > > if mem_is_zero() returns true here? > > This is an optimization in case of ack[] having no bits set (and also to > break from the loop acking->handling IRQs). I.e. if ack[] is zero the > AUX write to ack IRQs in intel_dp_ack_sink_irq_esi() can be skipped, > since no IRQ needs to be acked and then also no IRQ needs to be handled.
Okay, makes sense. Reviewed-by: Luca Coelho <luciano.coe...@intel.com> -- Cheers, Luca.