drm/i915: Adjust system agent voltage on CNL if required by DDI ports

On CNL we may need to bump up the system agent voltage not only due
to CDCLK but also when driving DDI port with a sufficiently high clock.
To that end start tracking the minimum acceptable voltage for each crtc.
We do the tracking via crtcs because we don't have any kind of encoder
state. Also there's no downside to doing it this way, and it matches how
we track cdclk requirements on account of pixel rate.

v2: Allow disabled crtcs to use the min voltage
    Add IS_CNL check to intel_ddi_compute_min_voltage() since
    we're using CNL specific values there
    s/intel_compute_min_voltage/cnl_compute_min_voltage/ since
    the function makes hw specific assumptions about the voltage
    values
v3: Drop the test hack leftovers from skl_modeset_calc_cdclk()
v4: s/voltage/voltage_level/ (Rodrigo)
    Replace DPLL DVFS FIXMEs with an explanation why we don't
    do anything there (Rodrigo)

Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171024095216.1638-9-ville.syrjala@linux.intel.com

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 772521440a9f..3d62c63c0763 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -34,6 +34,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 					struct intel_crtc_state *pipe_config,
 					struct drm_connector_state *conn_state)
 {
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
 	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
 	struct intel_digital_port *intel_dig_port = intel_mst->primary;
 	struct intel_dp *intel_dp = &intel_dig_port->dp;
@@ -87,6 +88,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
 	pipe_config->dp_m_n.tu = slots;
 
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
+
 	return true;
 }
 
@@ -307,6 +310,8 @@ static void intel_dp_mst_enc_get_config(struct intel_encoder *encoder,
 	intel_dp_get_m_n(crtc, pipe_config);
 
 	intel_ddi_clock_get(&intel_dig_port->base, pipe_config);
+
+	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
 }
 
 static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector)