drm/i915/pfit: Reject cloning when using pfit on ILK-BDW

The panel fitter lives inside the pipe and so would affect all cloned
outputs. However the relevant properties (scaling mode, TV margins)
are per-connector so we could end up with a situation where each cloned
output wants a different pfit configuration. Let's just reject pfit
usage with cloning entirely.

Currently not an issue as we don't yet expose the TV margin
properties, but if/when we add those to HDMI we could end up
in this situation. For eDP/DP we don't support cloning anyyway.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241016143134.26903-6-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index dc84389..593e419 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -474,6 +474,29 @@ static int intel_pch_pfit_check_timings(const struct intel_crtc_state *crtc_stat
        return 0;
 }
 
+static int intel_pch_pfit_check_cloning(const struct intel_crtc_state *crtc_state)
+{
+       struct intel_display *display = to_intel_display(crtc_state);
+       struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+
+       /*
+        * The panel fitter is in the pipe and thus would affect every
+        * cloned output. The relevant properties (scaling mode, TV
+        * margins) are per-connector so we'd have to make sure each
+        * output sets them up identically. Seems like a very niche use
+        * case so let's just reject cloning entirely when pfit is used.
+        */
+       if (crtc_state->uapi.encoder_mask &&
+           !is_power_of_2(crtc_state->uapi.encoder_mask)) {
+               drm_dbg_kms(display->drm,
+                           "[CRTC:%d:%s] no pfit when cloning\n",
+                           crtc->base.base.id, crtc->base.name);
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
 /* adjusted_mode has been preset to be the panel's fixed mode */
 static int pch_panel_fitting(struct intel_crtc_state *crtc_state,
                             const struct drm_connector_state *conn_state)
@@ -564,6 +587,10 @@ static int pch_panel_fitting(struct intel_crtc_state *crtc_state,
        if (ret)
                return ret;
 
+       ret = intel_pch_pfit_check_cloning(crtc_state);
+       if (ret)
+               return ret;
+
        return 0;
 }