This patch adds support for DPLL4 on EHL that include the
following restrictions:

- DPLL4 cannot be used with DDIA (combo port A internal eDP usage).
  DPLL4 can be used with other DDIs, including DDID
  (combo port A external usage).

- DPLL4 cannot be enabled when DC5 or DC6 are enabled.

- The DPLL4 enable, lock, power enabled, and power state are connected
  to the MGPLL1_ENABLE register.

v2: (suggestions from Bob Paauwe)
- Rework ehl_get_dpll() function to call intel_find_shared_dpll() and
  iterate twice: once for Combo plls and once for MG plls.

- Use MG pll funcs for DPLL4 instead of creating new ones and modify
  mg_pll_enable to include the restrictions for EHL.

Cc: Lucas De Marchi <lucas.demar...@intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasire...@intel.com>
Reviewed-by: Bob Paauwe <bob.j.paa...@intel.com>
---
 drivers/gpu/drm/i915/intel_dpll_mgr.c | 60 ++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c 
b/drivers/gpu/drm/i915/intel_dpll_mgr.c
index e01c057ce50b..cb756acedc94 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
@@ -2870,6 +2870,56 @@ icl_get_dpll(struct intel_crtc_state *crtc_state,
        return pll;
 }
 
+static struct intel_shared_dpll *
+ehl_get_dpll(struct intel_crtc_state *crtc_state,
+            struct intel_encoder *encoder)
+{
+       struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
+       struct intel_shared_dpll *pll;
+       enum port port = encoder->port;
+       enum intel_dpll_id min, max;
+       bool ret;
+
+       if (!intel_port_is_combophy(dev_priv, port)) {
+               MISSING_CASE(port);
+               return NULL;
+       }
+
+       min = DPLL_ID_ICL_DPLL0;
+       max = DPLL_ID_ICL_DPLL1;
+       ret = icl_calc_dpll_state(crtc_state, encoder);
+       if (ret) {
+               pll = intel_find_shared_dpll(crtc_state, min, max);
+               if (pll) {
+                       intel_reference_shared_dpll(pll, crtc_state);
+                       return pll;
+               }
+       } else {
+               DRM_DEBUG_KMS("Could not calculate PLL state.\n");
+       }
+
+       if (encoder->type == INTEL_OUTPUT_EDP) {
+               DRM_DEBUG_KMS("Cannot use DPLL4 with EDP.\n");
+               return NULL;
+       }
+
+       min = max = DPLL_ID_ICL_MGPLL1;
+       ret = icl_calc_mg_pll_state(crtc_state, false);
+       if (!ret) {
+               DRM_DEBUG_KMS("Could not calculate PLL state.\n");
+               return NULL;
+       }
+
+       pll = intel_find_shared_dpll(crtc_state, min, max);
+       if (!pll) {
+               DRM_DEBUG_KMS("No PLL selected\n");
+               return NULL;
+       }
+
+       intel_reference_shared_dpll(pll, crtc_state);
+       return pll;
+}
+
 static bool mg_pll_get_hw_state(struct drm_i915_private *dev_priv,
                                struct intel_shared_dpll *pll,
                                struct intel_dpll_hw_state *hw_state)
@@ -3115,6 +3165,13 @@ static void mg_pll_enable(struct drm_i915_private 
*dev_priv,
        i915_reg_t enable_reg =
                MG_PLL_ENABLE(icl_pll_id_to_tc_port(pll->info->id));
 
+       if (IS_ELKHARTLAKE(dev_priv) &&
+          (I915_READ(DC_STATE_EN) & DC_STATE_EN_UPTO_DC5 ||
+           I915_READ(DC_STATE_EN) & DC_STATE_EN_UPTO_DC6)) {
+               DRM_ERROR("Cant enable DPLL4 when DC5 or DC6 are enabled\n");
+               return;
+       }
+
        icl_pll_power_enable(dev_priv, pll, enable_reg);
 
        icl_mg_pll_write(dev_priv, pll);
@@ -3249,12 +3306,13 @@ static const struct intel_dpll_mgr icl_pll_mgr = {
 static const struct dpll_info ehl_plls[] = {
        { "DPLL 0", &combo_pll_funcs, DPLL_ID_ICL_DPLL0, 0 },
        { "DPLL 1", &combo_pll_funcs, DPLL_ID_ICL_DPLL1, 0 },
+       { "DPLL 4", &mg_pll_funcs, DPLL_ID_ICL_MGPLL1,0 },
        { },
 };
 
 static const struct intel_dpll_mgr ehl_pll_mgr = {
        .dpll_info = ehl_plls,
-       .get_dpll = icl_get_dpll,
+       .get_dpll = ehl_get_dpll,
        .dump_hw_state = icl_dump_hw_state,
 };
 
-- 
2.14.5

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