[PATCH 51/59] drm/i915/cnl: Fix DP max rate for Cannonlake with port F.

[Timo Aaltonen]

From: Rodrigo Vivi <rodrigo.vivi at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1757573

On CNL SKUs that uses port F,  max DP rate is 8.1G for all
ports when we have the elevated voltage (higher than 0.85V).

v2: Make commit message more generic.
v3: Move conditions to a helper to get easier to read. (Ville).
v4: Add a mention to the numerical voltage on commit
    message per Manasi request.
v5: Thanks CI! "error: control reaches end of non-void function"

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Cc: Manasi Navare <manasi.d.navare at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare at intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180129232223.766-10-rodrigo.vivi@intel.com
(backported from git://anongit.freedesktop.org/drm/drm-intel commit 53ddb3cdb063d7be74aa22ed831cad8aa5ee0863)
Signed-off-by: Timo Aaltonen <timo.aaltonen at canonical.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e8f544235984..54c834ed6427 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -216,15 +216,36 @@ intel_dp_downstream_max_dotclock(struct intel_dp *intel_dp)
 	return max_dotclk;
 }
 
+static int cnl_adjusted_max_rate(struct intel_dp *intel_dp, int size)
+{
+	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
+	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
+	enum port port = dig_port->base.port;
+
+	u32 voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
+
+	/* Low voltage SKUs are limited to max of 5.4G */
+	if (voltage == VOLTAGE_INFO_0_85V)
+		return size - 2;
+
+	/* For this SKU 8.1G is supported in all ports */
+	if (IS_CNL_WITH_PORT_F(dev_priv))
+		return size;
+
+	/* For other SKUs, max rate on ports A and B is 5.4G */
+	if (port == PORT_A || port == PORT_D)
+		return size - 2;
+
+	return size;
+}
+
 static void
 intel_dp_set_source_rates(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
 	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
-	enum port port = dig_port->port;
 	const int *source_rates;
 	int size;
-	u32 voltage;
 
 	/* This should only be done once */
 	WARN_ON(intel_dp->source_rates || intel_dp->num_source_rates);
@@ -234,11 +255,7 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
 		size = ARRAY_SIZE(bxt_rates);
 	} else if (IS_CANNONLAKE(dev_priv)) {
 		source_rates = cnl_rates;
-		size = ARRAY_SIZE(cnl_rates);
-		voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
-		if (port == PORT_A || port == PORT_D ||
-		    voltage == VOLTAGE_INFO_0_85V)
-			size -= 2;
+		size = cnl_adjusted_max_rate(intel_dp, ARRAY_SIZE(cnl_rates));
 	} else if (IS_GEN9_BC(dev_priv)) {
 		source_rates = skl_rates;
 		size = ARRAY_SIZE(skl_rates);
-- 
2.15.1