[Intel-gfx] [PATCH 3/3] drm/i915/dp: Disable Port sync mode correctly on teardown

[Manasi Navare]

While clearing the Ports ync mode enable and master select bits
we need to make sure that we perform a RMW for disable else
it sets the other bits casuing unwanted sideeffects.

Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/5
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Fixes: 51528afe7c5e ("drm/i915/display/icl: Disable transcoder port sync as part of crtc_disable() sequence")
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index c0a2dab3fe67..3fccda0f1f36 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -4599,7 +4599,8 @@ static void icl_disable_transcoder_port_sync(const struct intel_crtc_state *old_
 		      transcoder_name(old_crtc_state->cpu_transcoder));
 
 	reg = TRANS_DDI_FUNC_CTL2(old_crtc_state->cpu_transcoder);
-	trans_ddi_func_ctl2_val = ~(PORT_SYNC_MODE_ENABLE |
+	trans_ddi_func_ctl2_val = I915_READ(reg);
+	trans_ddi_func_ctl2_val &= ~(PORT_SYNC_MODE_ENABLE |
 				    PORT_SYNC_MODE_MASTER_SELECT_MASK);
 	I915_WRITE(reg, trans_ddi_func_ctl2_val);
 }
-- 
2.19.1