[PATCH 5/6] drm/i915/display: Add guardband check for feature latencies

[Ankit Nautiyal <ankit.k.nautiyal@intel.com>]

Add a check during atomic crtc check phase to ensure the programmed
guardband is sufficient to cover latencies introduced by enabled features
such as DSC, PSR/PR, scalers, and DP SDPs.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 56 ++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 4367ecfab2b3..4e3f08a8cd9c 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -126,6 +126,7 @@
 #include "intel_vga.h"
 #include "intel_vrr.h"
 #include "intel_wm.h"
+#include "skl_prefill.h"
 #include "skl_scaler.h"
 #include "skl_universal_plane.h"
 #include "skl_watermark.h"
@@ -4191,6 +4192,57 @@ static int hsw_compute_linetime_wm(struct intel_atomic_state *state,
 	return 0;
 }
 
+static int intel_crtc_guardband_atomic_check(struct intel_atomic_state *state,
+					     struct intel_crtc *crtc)
+{
+	struct intel_display *display = to_intel_display(crtc);
+	struct intel_crtc_state *crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct drm_display_mode *adjusted_mode =
+		&crtc_state->hw.adjusted_mode;
+	struct skl_prefill_ctx prefill_ctx;
+	int prefill_framestart_delay = 1;
+	int prefill_min_guardband;
+	int prefill_latency_us;
+	int prefill_wm0_lines;
+	int prefill_sagv_us;
+	int psr_latency = 0;
+	int sdp_latency = 0;
+	int min_guardband;
+	int guardband;
+
+	skl_prefill_init(&prefill_ctx, crtc_state);
+	prefill_wm0_lines = skl_wm0_prefill_lines(crtc_state);
+	prefill_sagv_us = display->sagv.block_time_us;
+	prefill_latency_us = prefill_sagv_us +
+			     intel_scanlines_to_usecs(adjusted_mode,
+						      prefill_framestart_delay +
+						      prefill_wm0_lines);
+	prefill_min_guardband =
+		skl_prefill_min_guardband(&prefill_ctx,
+					  crtc_state,
+					  prefill_latency_us);
+
+	if (intel_crtc_has_dp_encoder(crtc_state)) {
+		psr_latency = intel_psr_max_link_wake_latency(crtc_state);
+		sdp_latency = intel_dp_compute_sdp_latency(crtc_state);
+	}
+
+	min_guardband = max(sdp_latency, psr_latency);
+
+	min_guardband = max(min_guardband, prefill_min_guardband);
+
+	guardband = intel_crtc_vblank_length(crtc_state);
+
+	if (guardband < min_guardband) {
+		drm_dbg_kms(display->drm, "actual guardband: %d shorter than min guardband: %d\n",
+			    guardband, min_guardband);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int intel_crtc_atomic_check(struct intel_atomic_state *state,
 				   struct intel_crtc *crtc)
 {
@@ -4253,6 +4305,10 @@ static int intel_crtc_atomic_check(struct intel_atomic_state *state,
 	if (ret)
 		return ret;
 
+	ret = intel_crtc_guardband_atomic_check(state, crtc);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
-- 
2.45.2