drm/i915: Check PSR setup time vs. vblank length

Bspec says:
"Restriction : SRD must not be enabled when the PSR Setup time from DPCD
00071h is greater than the time for vertical blank minus one line."

Let's check for that and disallow PSR if we exceed the limit.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/intel_drv.h

@@ -1730,6 +1730,8 @@ bool intel_sdvo_init(struct drm_device *dev,
 
 
 /* intel_sprite.c */
+int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
+			     int usecs);
 int intel_plane_init(struct drm_device *dev, enum pipe pipe, int plane);
 int intel_sprite_set_colorkey(struct drm_device *dev, void *data,
 			      struct drm_file *file_priv);

drivers/gpu/drm/i915/intel_psr.c

@@ -327,6 +327,9 @@ static bool intel_psr_match_conditions(struct intel_dp *intel_dp)
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_crtc *crtc = dig_port->base.base.crtc;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	const struct drm_display_mode *adjusted_mode =
+		&intel_crtc->config->base.adjusted_mode;
+	int psr_setup_time;
 
 	lockdep_assert_held(&dev_priv->psr.lock);
 	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
@@ -365,11 +368,25 @@ static bool intel_psr_match_conditions(struct intel_dp *intel_dp)
 	}
 
 	if (IS_HASWELL(dev) &&
-	    intel_crtc->config->base.adjusted_mode.flags & DRM_MODE_FLAG_INTERLACE) {
+	    adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE) {
 		DRM_DEBUG_KMS("PSR condition failed: Interlaced is Enabled\n");
 		return false;
 	}
 
+	psr_setup_time = drm_dp_psr_setup_time(intel_dp->psr_dpcd);
+	if (psr_setup_time < 0) {
+		DRM_DEBUG_KMS("PSR condition failed: Invalid PSR setup time (0x%02x)\n",
+			      intel_dp->psr_dpcd[1]);
+		return false;
+	}
+
+	if (intel_usecs_to_scanlines(adjusted_mode, psr_setup_time) >
+	    adjusted_mode->crtc_vtotal - adjusted_mode->crtc_vdisplay - 1) {
+		DRM_DEBUG_KMS("PSR condition failed: PSR setup time (%d us) too long\n",
+			      psr_setup_time);
+		return false;
+	}
+
 	dev_priv->psr.source_ok = true;
 	return true;
 }

drivers/gpu/drm/i915/intel_sprite.c

@@ -53,8 +53,8 @@ format_is_yuv(uint32_t format)
 	}
 }
 
-static int usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
-			      int usecs)
+int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
+			     int usecs)
 {
 	/* paranoia */
 	if (!adjusted_mode->crtc_htotal)
@@ -91,7 +91,7 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
 		vblank_start = DIV_ROUND_UP(vblank_start, 2);
 
 	/* FIXME needs to be calibrated sensibly */
-	min = vblank_start - usecs_to_scanlines(adjusted_mode, 100);
+	min = vblank_start - intel_usecs_to_scanlines(adjusted_mode, 100);
 	max = vblank_start - 1;
 
 	local_irq_disable();