As it turns out, the aux block being off was not the real problem here, as transition from D3 to D0 is mandated by the DP spec to take a maximum of 1ms, whereas we're allowed a 100ms timeframe to respond to ESI irqs. The real problem here is a bit more subtle.

When doing a modeset where the problem of the sink timing out to our sideband requests when transitioning from D3 to D0 occurs, the timeout is from the aux block not coming on. However, nothing else times out other than the initial phy_up message because the DPCD on call in intel_ddi_enable_dp() ends up waking up the AUX block on the hub, not the phy_up sideband message. This means that the real fix we need is to use the DPMS on before sending a phy_up to ensure that the hub is ready to accept sideband messages.

Signed-off-by: Lyude Paul lyude@redhat.com Cc: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Laura Abbott labbott@redhat.com Cc: stable@vger.kernel.org Fixes: ad260ab32a4d9 ("drm/i915/dp: Write to SET_POWER dpcd to enable MST hub.") --- Sorry for all the spam guys! This is my last attempt at getting this patch to actually come up on intel-gfx's patchwork page instead of dri-devel. I have no idea what is going on with patchwork right now :|, but maybe removing dri-devel from the CC entirely will help.

drivers/gpu/drm/i915/intel_ddi.c | 6 +++++- drivers/gpu/drm/i915/intel_dp_mst.c | 1 + 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index a6672a9abd85..9bd675f73f7b 100644 --- a/drivers/gpu/drm/i915/intel_ddi.c +++ b/drivers/gpu/drm/i915/intel_ddi.c @@ -2324,7 +2324,11 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder, intel_prepare_dp_ddi_buffers(encoder, crtc_state);

intel_ddi_init_dp_buf_reg(encoder); - intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON); + /* for MST, we do DPMS_ON outside of here so that DPMS_ON can happen + * before drm_dp_send_power_updown_phy() + */ + if (!intel_dp->is_mst) + intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON); intel_dp_start_link_train(intel_dp); if (port != PORT_A || INTEL_GEN(dev_priv) >= 9) intel_dp_stop_link_train(intel_dp); diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c index c3de0918ee13..eff9a4eae1f0 100644 --- a/drivers/gpu/drm/i915/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/intel_dp_mst.c @@ -223,6 +223,7 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder,

DRM_DEBUG_KMS("active links %d\n", intel_dp->active_mst_links);

+ intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON); drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true); if (intel_dp->active_mst_links == 0) intel_dig_port->base.pre_enable(&intel_dig_port->base,