drm/i915/lobf: Update lobf if any change in dependent parameters

For every commit the dependent condition for LOBF is checked
and accordingly update has_lobf flag which will be used
to update the ALPM_CTL register during commit.

v1: Initial version.
v2: Avoid reading h/w register without has_lobf check. [Jani]
v3: Update LOBF in post plane update instead of separate function. [Jouni]
v4:
- Add lobf disable print. [Jouni]
- Simplify condition check for enabling/disabling lobf. [Jouni]
v5: Disable LOBF in pre_plane_update(). [Jouni]
v6: use lobf flag of old_crtc_state and write 0 into ALPM_CTL. [Jouni]

Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/20250423092334.2294483-7-animesh.manna@intel.com

3 files changed, 43 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c b/drivers/gpu/drm/i915/display/intel_alpm.c
index 01949b90c0c3..d38e729682ce 100644
--- a/drivers/gpu/drm/i915/display/intel_alpm.c
+++ b/drivers/gpu/drm/i915/display/intel_alpm.c
@@ -376,15 +376,54 @@ void intel_alpm_configure(struct intel_dp *intel_dp,
 	intel_dp->alpm_parameters.transcoder = crtc_state->cpu_transcoder;
 }
 
+void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
+				 struct intel_crtc *crtc)
+{
+	struct intel_display *display = to_intel_display(state);
+	const struct intel_crtc_state *crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct intel_crtc_state *old_crtc_state =
+		intel_atomic_get_old_crtc_state(state, crtc);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+	struct intel_encoder *encoder;
+
+	if (DISPLAY_VER(display) < 20)
+		return;
+
+	if (crtc_state->has_lobf || crtc_state->has_lobf == old_crtc_state->has_lobf)
+		return;
+
+	for_each_intel_encoder_mask(display->drm, encoder,
+				    crtc_state->uapi.encoder_mask) {
+		struct intel_dp *intel_dp;
+
+		if (!intel_encoder_is_dp(encoder))
+			continue;
+
+		intel_dp = enc_to_intel_dp(encoder);
+
+		if (!intel_dp_is_edp(intel_dp))
+			continue;
+
+		if (old_crtc_state->has_lobf) {
+			intel_de_write(display, ALPM_CTL(display, cpu_transcoder), 0);
+			drm_dbg_kms(display->drm, "Link off between frames (LOBF) disabled\n");
+		}
+	}
+}
+
 void intel_alpm_post_plane_update(struct intel_atomic_state *state,
 				  struct intel_crtc *crtc)
 {
 	struct intel_display *display = to_intel_display(state);
 	const struct intel_crtc_state *crtc_state =
 		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct intel_crtc_state *old_crtc_state =
+		intel_atomic_get_old_crtc_state(state, crtc);
 	struct intel_encoder *encoder;
 
-	if (!crtc_state->has_lobf && !crtc_state->has_psr)
+	if ((!crtc_state->has_lobf ||
+	     crtc_state->has_lobf == old_crtc_state->has_lobf) && !crtc_state->has_psr)
 		return;
 
 	for_each_intel_encoder_mask(display->drm, encoder,
diff --git a/drivers/gpu/drm/i915/display/intel_alpm.h b/drivers/gpu/drm/i915/display/intel_alpm.h
index 91f51fb24f98..77bae022a0ea 100644
--- a/drivers/gpu/drm/i915/display/intel_alpm.h
+++ b/drivers/gpu/drm/i915/display/intel_alpm.h
@@ -23,6 +23,8 @@ void intel_alpm_lobf_compute_config(struct intel_dp *intel_dp,
 				    struct drm_connector_state *conn_state);
 void intel_alpm_configure(struct intel_dp *intel_dp,
 			  const struct intel_crtc_state *crtc_state);
+void intel_alpm_pre_plane_update(struct intel_atomic_state *state,
+				 struct intel_crtc *crtc);
 void intel_alpm_post_plane_update(struct intel_atomic_state *state,
 				  struct intel_crtc *crtc);
 void intel_alpm_lobf_debugfs_add(struct intel_connector *connector);
diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index b91a52e9909a..58845b74f17d 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -1176,6 +1176,7 @@ static void intel_pre_plane_update(struct intel_atomic_state *state,
 		intel_atomic_get_new_crtc_state(state, crtc);
 	enum pipe pipe = crtc->pipe;
 
+	intel_alpm_pre_plane_update(state, crtc);
 	intel_psr_pre_plane_update(state, crtc);
 
 	if (intel_crtc_vrr_disabling(state, crtc)) {