linux-kernel - [PATCH 1/2] drm/i915/skl: Don't skip mst encoders in skl_ddi_pll

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Date:	Tue,  2 Feb 2016 09:35:08 -0500
From:	Lyude <cpaul@...hat.com>
To:	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, David Airlie <airlied@...hat.com>
Cc:	Rob Clark <rclark@...hat.com>, Adam Jackson <ajax@...hat.com>,
	Lyude <cpaul@...hat.com>
Subject: [PATCH 1/2] drm/i915/skl: Don't skip mst encoders in skl_ddi_pll_select()

We don't actually check for INTEL_OUTPUT_DP_MST at all in here, as a
result we skip assigning a DPLL to any DP MST ports, which makes link
training fail, after which things just keep going downhill from there.

Consequently, this fixes DisplayPort MST causing kernel panics, machine
check errors, etc. on Skylake.

Signed-off-by: Lyude <cpaul@...hat.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index e6408e5..54a165b 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1589,7 +1589,8 @@ skl_ddi_pll_select(struct intel_crtc *intel_crtc,
 			 DPLL_CFGCR2_KDIV(wrpll_params.kdiv) |
 			 DPLL_CFGCR2_PDIV(wrpll_params.pdiv) |
 			 wrpll_params.central_freq;
-	} else if (intel_encoder->type == INTEL_OUTPUT_DISPLAYPORT) {
+	} else if (intel_encoder->type == INTEL_OUTPUT_DISPLAYPORT ||
+		   intel_encoder->type == INTEL_OUTPUT_DP_MST) {
 		switch (crtc_state->port_clock / 2) {
 		case 81000:
 			ctrl1 |= DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_810, 0);
-- 
2.5.0