Currently the EMP_AS_SDP_TL is set to vrr.vsync_start which is
incorrect.

As per Bspec:71197 the transmission line must be within the SCL +
guardband region. Before guardband optimization, guradband was same as
vblank length so EMP_AS_SDP_TL set with vrr.sync_start was falling in
this region and it was not giving an issue.

Now with optimized guardband, this is falling outside the SCL +
guardband region and since the same transmission line is used by VSC SDP
also, this results in PSR timeout issues.

Further restrictions on the position of the transmission line:
For DP/eDP, if there is a set context latency (SCL) window, then it
cannot be the first line of SCL
For DP/eDP, if there is no SCL window, then it cannot be the first line of
the Delayed V. Blank

Fix the EMP_AS_SDP_TL to VTOTAL - (delayed vblank_start - SCL + 1)
Internally the HW computes the value as VTOTAL - EMP_AS_SDP_TL.

Fixes: e1123e617e51 ("drm/i915/vrr: Program EMP_AS_SDP_TL for DP AS SDP")
Cc: Ankit Nautiyal <[email protected]>
Cc: Jouni Högander <[email protected]>
Signed-off-by: Ankit Nautiyal <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_vrr.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c 
b/drivers/gpu/drm/i915/display/intel_vrr.c
index 92fb72b56f16..dd81d2133aba 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -655,18 +655,24 @@ void intel_vrr_set_db_point_and_transmission_line(const 
struct intel_crtc_state
 {
        struct intel_display *display = to_intel_display(crtc_state);
        enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+       const struct drm_display_mode *adjusted_mode = 
&crtc_state->hw.adjusted_mode;
+       int transmission_line;
 
        /*
         * For BMG and LNL+ onwards the EMP_AS_SDP_TL is used for programming
         * double buffering point and transmission line for VRR packets for
         * HDMI2.1/DP/eDP/DP->HDMI2.1 PCON.
         * Since currently we support VRR only for DP/eDP, so this is programmed
-        * to for Adaptive Sync SDP to Vsync start.
+        * for Adaptive Sync SDP.
         */
-       if (DISPLAY_VERx100(display) == 1401 || DISPLAY_VER(display) >= 20)
+       if (DISPLAY_VERx100(display) == 1401 || DISPLAY_VER(display) >= 20) {
+               transmission_line = adjusted_mode->crtc_vtotal - 
(adjusted_mode->crtc_vblank_start -
+                                                                 
crtc_state->set_context_latency +
+                                                                 1);
                intel_de_write(display,
                               EMP_AS_SDP_TL(display, cpu_transcoder),
-                              EMP_AS_SDP_DB_TL(crtc_state->vrr.vsync_start));
+                              EMP_AS_SDP_DB_TL(transmission_line));
+       }
 }
 
 static int intel_vrr_hw_vmin(const struct intel_crtc_state *crtc_state)
-- 
2.45.2

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