drm/i915/alpm: Add compute config for lobf

Link Off Between Active Frames, is a new feature for eDP
that allows the panel to go to lower power state after
transmission of data. This is a feature on top of ALPM, AS SDP.
Add compute config during atomic-check phase.

v1: RFC version.
v2: Add separate flag for auxless-alpm. [Jani]
v3:
- intel_dp->lobf_supported replaced with crtc_state->has_lobf. [Jouni]
- Add DISPLAY_VER() check. [Jouni]
- Modify function name of get_aux_less_status. [Jani]
v4: Add enum alpm_mode to hold the aux-wake/less capability.
v5: Add alpm_dpcd to intel_dp and use aux_wake_supported()/
aux_less_wake_supported() instead of enum alpm_mode. [Jouni]
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240529200742.1694401-5-animesh.manna@intel.com

drivers/gpu/drm/i915/display/intel_alpm.c

@@ -11,6 +11,26 @@
 #include "intel_dp_aux.h"
 #include "intel_psr_regs.h"
 
+static bool intel_alpm_aux_wake_supported(struct intel_dp *intel_dp)
+{
+	return intel_dp->alpm_dpcd & DP_ALPM_CAP;
+}
+
+static bool intel_alpm_aux_less_wake_supported(struct intel_dp *intel_dp)
+{
+	return intel_dp->alpm_dpcd & DP_ALPM_AUX_LESS_CAP;
+}
+
+void intel_alpm_init_dpcd(struct intel_dp *intel_dp)
+{
+	u8 dpcd;
+
+	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_RECEIVER_ALPM_CAP, &dpcd) < 0)
+		return;
+
+	intel_dp->alpm_dpcd = dpcd;
+}
+
 /*
  * See Bspec: 71632 for the table
  *
@@ -243,6 +263,47 @@ bool intel_alpm_compute_params(struct intel_dp *intel_dp,
 	return true;
 }
 
+void intel_alpm_lobf_compute_config(struct intel_dp *intel_dp,
+				    struct intel_crtc_state *crtc_state,
+				    struct drm_connector_state *conn_state)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+	int waketime_in_lines, first_sdp_position;
+	int context_latency, guardband;
+
+	if (!intel_dp_is_edp(intel_dp))
+		return;
+
+	if (DISPLAY_VER(i915) < 20)
+		return;
+
+	if (!intel_dp_as_sdp_supported(intel_dp))
+		return;
+
+	if (crtc_state->has_psr)
+		return;
+
+	if (!(intel_alpm_aux_wake_supported(intel_dp) ||
+	      intel_alpm_aux_less_wake_supported(intel_dp)))
+		return;
+
+	if (!intel_alpm_compute_params(intel_dp, crtc_state))
+		return;
+
+	context_latency = adjusted_mode->crtc_vblank_start - adjusted_mode->crtc_vdisplay;
+	guardband = adjusted_mode->crtc_vtotal -
+		    adjusted_mode->crtc_vdisplay - context_latency;
+	first_sdp_position = adjusted_mode->crtc_vtotal - adjusted_mode->crtc_vsync_start;
+	if (intel_alpm_aux_less_wake_supported(intel_dp))
+		waketime_in_lines = intel_dp->alpm_parameters.io_wake_lines;
+	else
+		waketime_in_lines = intel_dp->alpm_parameters.fast_wake_lines;
+
+	crtc_state->has_lobf = (context_latency + guardband) >
+		(first_sdp_position + waketime_in_lines);
+}
+
 static void lnl_alpm_configure(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);

drivers/gpu/drm/i915/display/intel_alpm.h

@@ -10,9 +10,14 @@
 
 struct intel_dp;
 struct intel_crtc_state;
+struct drm_connector_state;
 
+void intel_alpm_init_dpcd(struct intel_dp *intel_dp);
 bool intel_alpm_compute_params(struct intel_dp *intel_dp,
 			       struct intel_crtc_state *crtc_state);
+void intel_alpm_lobf_compute_config(struct intel_dp *intel_dp,
+				    struct intel_crtc_state *crtc_state,
+				    struct drm_connector_state *conn_state);
 void intel_alpm_configure(struct intel_dp *intel_dp);
 
 #endif

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1410,6 +1410,9 @@ struct intel_crtc_state {
 
 	/* for loading single buffered registers during vblank */
 	struct drm_vblank_work vblank_work;
+
+	/* LOBF flag */
+	bool has_lobf;
 };
 
 enum intel_pipe_crc_source {
@@ -1846,6 +1849,8 @@ struct intel_dp {
 		u8 silence_period_sym_clocks;
 		u8 lfps_half_cycle_num_of_syms;
 	} alpm_parameters;
+
+	u8 alpm_dpcd;
 };
 
 enum lspcon_vendor {

drivers/gpu/drm/i915/display/intel_dp.c

@@ -48,6 +48,7 @@
 #include "i915_drv.h"
 #include "i915_irq.h"
 #include "i915_reg.h"
+#include "intel_alpm.h"
 #include "intel_atomic.h"
 #include "intel_audio.h"
 #include "intel_backlight.h"
@@ -3000,6 +3001,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	intel_vrr_compute_config(pipe_config, conn_state);
 	intel_dp_compute_as_sdp(intel_dp, pipe_config);
 	intel_psr_compute_config(intel_dp, pipe_config, conn_state);
+	intel_alpm_lobf_compute_config(intel_dp, pipe_config, conn_state);
 	intel_dp_drrs_compute_config(connector, pipe_config, link_bpp_x16);
 	intel_dp_compute_vsc_sdp(intel_dp, pipe_config, conn_state);
 	intel_dp_compute_hdr_metadata_infoframe_sdp(intel_dp, pipe_config, conn_state);
@@ -6513,6 +6515,8 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	 */
 	intel_hpd_enable_detection(encoder);
 
+	intel_alpm_init_dpcd(intel_dp);
+
 	/* Cache DPCD and EDID for edp. */
 	has_dpcd = intel_edp_init_dpcd(intel_dp, intel_connector);