From: Ville Syrjälä ville.syrjala@linux.intel.com

Currently we allow DRRS on IVB PCH ports, but we're missing a few programming steps meaning it is guaranteed to not work. And on HSW DRRS is not supported on anything but port A ever as only transcoder EDP has the M2/N2 registers (though I'm not sure if HSW ever has eDP on any other port).

Starting from BDW all transcoders have the dynamically reprogrammable M/N registers so DRRS could work on any port.

Stop initializing DRRS on ports where it cannot possibly work.

Cc: stable@vger.kernel.org Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com --- drivers/gpu/drm/i915/display/intel_drrs.c | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_drrs.c b/drivers/gpu/drm/i915/display/intel_drrs.c index 53f014b4436b..9f673255578e 100644 --- a/drivers/gpu/drm/i915/display/intel_drrs.c +++ b/drivers/gpu/drm/i915/display/intel_drrs.c @@ -413,6 +413,7 @@ intel_drrs_init(struct intel_connector *connector, struct drm_display_mode *fixed_mode) { struct drm_i915_private *dev_priv = to_i915(connector->base.dev); + struct intel_encoder *encoder = connector->encoder; struct drm_display_mode *downclock_mode = NULL;

INIT_DELAYED_WORK(&dev_priv->drrs.work, intel_drrs_downclock_work); @@ -424,6 +425,13 @@ intel_drrs_init(struct intel_connector *connector, return NULL; }

+ if ((DISPLAY_VER(dev_priv) < 8 && !HAS_GMCH(dev_priv)) && + encoder->port != PORT_A) { + drm_dbg_kms(&dev_priv->drm, + "DRRS only supported on eDP port A\n"); + return NULL; + } + if (dev_priv->vbt.drrs_type != SEAMLESS_DRRS_SUPPORT) { drm_dbg_kms(&dev_priv->drm, "VBT doesn't support DRRS\n"); return NULL;