FAILED: patch "[PATCH] drm/i915/dp: Write to SET_POWER dpcd to enable MST hub." failed to apply to 4.16-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.16-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 7a7d58dc2997b6ca5bc1eaa4bd8d019cf7c4a148 Mon Sep 17 00:00:00 2001
From: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Date: Tue, 13 Mar 2018 22:48:25 -0700
Subject: [PATCH] drm/i915/dp: Write to SET_POWER dpcd to enable MST hub.
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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.

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
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-dhinakaran.pandiyan@intel.com
(cherry picked from commit ad260ab32a4d94fa974f58262f8000472d34fd5b)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index dbcf1a0586f9..8c2d778560f0 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2205,8 +2205,7 @@ 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);
-	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);
@@ -2304,14 +2303,12 @@ 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;
-	bool is_mst = intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DP_MST);
 
 	/*
 	 * 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);