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.syrj...@linux.intel.com>
Cc: Lucas De Marchi <lucas.demar...@intel.com>
Cc: Manasi Navare <manasi.d.nav...@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.v...@intel.com>
Reviewed-by: Manasi Navare <manasi.d.nav...@intel.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 86a5e8bfe2a6..1f10bdb855e7 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -220,15 +220,36 @@ 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->base.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);
@@ -238,11 +259,7 @@ 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);
-- 
2.13.6

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