DK, please start stable backport commit messages with:

commit b1e314462bba76660eec62760bb2e87f28f58866 upstream.

Referencing the upstream commit.

BR, Jani.

On Thu, 29 Mar 2018, Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com wrote:

If bios sets up an MST output and hardware state readout code sees this is an SST configuration, when disabling the encoder we end up calling ->post_disable_dp() hook instead of the MST version. Consequently, we write to the DP_SET_POWER dpcd to set it D3 state. Further along when we try enable the encoder in MST mode, POWER_UP_PHY transaction fails to power up the MST hub. This results in continuous link training failures which keep the system busy delaying boot. We could identify bios MST boot discrepancy and handle it accordingly but a simple way to solve this is to write to the DP_SET_POWER dpcd for MST too.

v2: Rebased on stable/linux-4.15.y and fixed minor conflict.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105470 Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Jani Nikula jani.nikula@intel.com Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Reported-by: Laura Abbott labbott@redhat.com Cc: stable@vger.kernel.org # 4.15+ Fixes: 5ea2355a100a ("drm/i915/mst: Use MST sideband message transactions for dpms control") Tested-by: Laura Abbott labbott@redhat.com Signed-off-by: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com Signed-off-by: Jani Nikula jani.nikula@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20180314054825.1718-1-dhinakar... (cherry picked from commit ad260ab32a4d94fa974f58262f8000472d34fd5b) Signed-off-by: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com

---

drivers/gpu/drm/i915/intel_ddi.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index 58a3755544b2..38e53d6b8127 100644 --- a/drivers/gpu/drm/i915/intel_ddi.c +++ b/drivers/gpu/drm/i915/intel_ddi.c @@ -2208,8 +2208,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder, intel_prepare_dp_ddi_buffers(encoder); intel_ddi_init_dp_buf_reg(encoder);

• if (!is_mst)

• intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
  

• 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);

@@ -2294,19 +2293,12 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder, struct drm_i915_private *dev_priv = to_i915(encoder->base.dev); struct intel_digital_port *dig_port = enc_to_dig_port(&encoder->base); struct intel_dp *intel_dp = &dig_port->dp;

• /*

• * old_crtc_state and old_conn_state are NULL when called from
  

• * DP_MST. The main connector associated with this port is never
  

• * bound to a crtc for MST.
  

• */
  

• bool is_mst = !old_crtc_state;

/* * Power down sink before disabling the port, otherwise we end * up getting interrupts from the sink on detecting link loss. */

• if (!is_mst)

• intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
  

• intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);

intel_disable_ddi_buf(encoder);