[PATCH v3 08/10] drm/i915/display: Implement Wa_14021768792 for BMG DP for link_m/n ratio > 10

[Suraj Kandpal <suraj.kandpal@intel.com>]

From: Ankit Nautiyal <ankit.k.nautiyal@intel.com>

Handle the bypass logic for the M/N ratio limit for DP.
Calculate the M/N ratio, check if it can bypass the limit, and set the
appropriate flags for the workaround.

The workaround is only intended for 128b/132b links, so restrict it to
those.

Bspec also restricts the Link M/N values from changing outside of a
modeset while the mechanism is active, so disable DRRS and the seamless
M/N fastset path for such a configuration.

Bspec: 49266
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 26 ++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 8de51582d18c..3911942de8e5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -3373,6 +3373,9 @@ static bool can_enable_drrs(struct intel_connector *connector,
 	if (pipe_config->vrr.enable)
 		return false;
 
+	if (pipe_config->dp_m_n.bypass_m_n_ratio_limit)
+		return false;
+
 	/*
 	 * DRRS and PSR can't be enable together, so giving preference to PSR
 	 * as it allows more power-savings by complete shutting down display,
@@ -3397,6 +3400,7 @@ void intel_dp_check_m_n_ratio(struct intel_crtc_state *crtc_state,
 			      struct intel_link_m_n *m_n)
 {
 	struct intel_display *display = to_intel_display(crtc_state);
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
 	int max_m_n_ratio = intel_dp_get_max_m_n_ratio(display);
 	int m_n_ratio;
 
@@ -3405,10 +3409,21 @@ void intel_dp_check_m_n_ratio(struct intel_crtc_state *crtc_state,
 
 	m_n_ratio = DIV_ROUND_UP(m_n->link_m, m_n->link_n);
 
-	if (m_n_ratio > max_m_n_ratio)
-		drm_WARN(display->drm, 1,
-			 "Link M/N ratio (%d) exceeds max allowed (%d)\n",
-			 m_n_ratio, max_m_n_ratio);
+	if (m_n_ratio <= max_m_n_ratio)
+		return;
+
+	if (intel_dp_is_uhbr(crtc_state) &&
+	    intel_display_can_bypass_m_n_limit(display, m_n_ratio, crtc->pipe)) {
+		m_n->bypass_m_n_ratio_limit = true;
+		drm_dbg_kms(display->drm,
+			    "Bypassing Link_m/Link_n ratio limit (ratio %d)\n",
+			    m_n_ratio);
+		return;
+	}
+
+	drm_WARN(display->drm, 1,
+		 "Link M/N ratio (%d) exceeds max allowed (%d)\n",
+		 m_n_ratio, max_m_n_ratio);
 }
 
 static void
@@ -3425,7 +3440,8 @@ intel_dp_drrs_compute_config(struct intel_connector *connector,
 	 * FIXME all joined pipes share the same transcoder.
 	 * Need to account for that when updating M/N live.
 	 */
-	if (has_seamless_m_n(connector) && !pipe_config->joiner_pipes)
+	if (has_seamless_m_n(connector) && !pipe_config->joiner_pipes &&
+	    !pipe_config->dp_m_n.bypass_m_n_ratio_limit)
 		pipe_config->update_m_n = true;
 
 	if (!can_enable_drrs(connector, pipe_config, downclock_mode)) {
-- 
2.34.1