drm/i915/ddi: Simplify the port enabling via DDI_BUF_CTL

In the past intel_digital_port::dp.prepare_link_retrain() could be
called directly (vs. from a modeset) to retrain an enabled link. In that
case the port had to be first disabled and then re-enabled. That changed
with commit 2885d283cce5 ("drm/i915/dp: Retrain SST links via a modeset
commit"), after which the only way prepare_link_retrain() can be called
is from a modeset during link training when the port is still disabled.
Simplify things accordingly, assuming the disabled port state.

v2: Don't use drm_i915_private in intel_ddi_prepare_link_retrain(). (Jani)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214142001.552916-6-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index bf1c16b496cdb028dcefb26bb73fbd4b912c75b8..5d008c04ca2d2997bda61bb697e786c3c76fad9f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -3761,8 +3761,8 @@ static void mtl_ddi_prepare_link_retrain(struct intel_dp *intel_dp,
         * necessary disable and enable port
         */
        dp_tp_ctl = intel_de_read(display, dp_tp_ctl_reg(encoder, crtc_state));
-       if (dp_tp_ctl & DP_TP_CTL_ENABLE)
-               mtl_disable_ddi_buf(encoder, crtc_state);
+
+       drm_WARN_ON(display->drm, dp_tp_ctl & DP_TP_CTL_ENABLE);
 
        /* 6.d Configure and enable DP_TP_CTL with link training pattern 1 selected */
        dp_tp_ctl = DP_TP_CTL_ENABLE | DP_TP_CTL_LINK_TRAIN_PAT1;
@@ -3801,30 +3801,16 @@ static void mtl_ddi_prepare_link_retrain(struct intel_dp *intel_dp,
 static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp,
                                           const struct intel_crtc_state *crtc_state)
 {
+       struct intel_display *display = to_intel_display(intel_dp);
        struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
        struct intel_encoder *encoder = &dig_port->base;
        struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
        enum port port = encoder->port;
-       u32 dp_tp_ctl, ddi_buf_ctl;
-       bool wait = false;
+       u32 dp_tp_ctl;
 
        dp_tp_ctl = intel_de_read(dev_priv, dp_tp_ctl_reg(encoder, crtc_state));
 
-       if (dp_tp_ctl & DP_TP_CTL_ENABLE) {
-               ddi_buf_ctl = intel_de_read(dev_priv, DDI_BUF_CTL(port));
-               if (ddi_buf_ctl & DDI_BUF_CTL_ENABLE) {
-                       intel_de_write(dev_priv, DDI_BUF_CTL(port),
-                                      ddi_buf_ctl & ~DDI_BUF_CTL_ENABLE);
-                       wait = true;
-               }
-
-               dp_tp_ctl &= ~DP_TP_CTL_ENABLE;
-               intel_de_write(dev_priv, dp_tp_ctl_reg(encoder, crtc_state), dp_tp_ctl);
-               intel_de_posting_read(dev_priv, dp_tp_ctl_reg(encoder, crtc_state));
-
-               if (wait)
-                       intel_wait_ddi_buf_idle(dev_priv, port);
-       }
+       drm_WARN_ON(display->drm, dp_tp_ctl & DP_TP_CTL_ENABLE);
 
        dp_tp_ctl = DP_TP_CTL_ENABLE | DP_TP_CTL_LINK_TRAIN_PAT1;
        if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST) ||