[PATCH v4 8/9] drm/i915/vrr: Program CMRR enable/disable from transcoder timings

[Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>]

Split the CMRR M/N register programming into intel_vrr_enable_cmrr()
and intel_vrr_disable_cmrr(), and drive them from
intel_vrr_set_fixed_rr_timings() based on crtc_state->vrr.cmrr.enable.

VRR_CTL_CMRR_ENABLE is not set explicitly, writing TRANS_CMRR_N_HI
arms CMRR in hardware. Drop the now-unused cmrr_enable
argument to intel_vrr_tg_enable().

No functional change intended for non-CMRR configurations.

--v2:
- Commit message changes.
- Added Simplified enable/disable sequence. (Chaitanya)

--v3:
- Guard CMRR enable condition (Chaitanya)
- Comment changes updated (Chaitanya)
- Squash register write commits together and
avoid double writing issue. (Chaitanya)

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Assisted-by: Claude:claude-opus-4-8
---
 drivers/gpu/drm/i915/display/intel_vrr.c | 60 ++++++++++++++++--------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
index fa9d1a57f438..ae9824e679f3 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -188,6 +188,34 @@ int intel_vrr_vmax_vblank_start(const struct intel_crtc_state *crtc_state)
 	return intel_vrr_vmax_vtotal(crtc_state) - crtc_state->vrr.guardband;
 }
 
+static void
+intel_vrr_enable_cmrr(const struct intel_crtc_state *crtc_state)
+{
+	struct intel_display *display = to_intel_display(crtc_state);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+
+	intel_de_write(display, TRANS_CMRR_M_HI(display, cpu_transcoder),
+		       upper_32_bits(crtc_state->vrr.cmrr.cmrr_m));
+	intel_de_write(display, TRANS_CMRR_M_LO(display, cpu_transcoder),
+		       lower_32_bits(crtc_state->vrr.cmrr.cmrr_m));
+	intel_de_write(display, TRANS_CMRR_N_LO(display, cpu_transcoder),
+		       lower_32_bits(crtc_state->vrr.cmrr.cmrr_n));
+	intel_de_write(display, TRANS_CMRR_N_HI(display, cpu_transcoder),
+		       upper_32_bits(crtc_state->vrr.cmrr.cmrr_n));
+}
+
+static void
+intel_vrr_disable_cmrr(const struct intel_crtc_state *crtc_state)
+{
+	struct intel_display *display = to_intel_display(crtc_state);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+
+	intel_de_write(display, TRANS_CMRR_M_HI(display, cpu_transcoder), 0);
+	intel_de_write(display, TRANS_CMRR_M_LO(display, cpu_transcoder), 0);
+	intel_de_write(display, TRANS_CMRR_N_LO(display, cpu_transcoder), 0);
+	intel_de_write(display, TRANS_CMRR_N_HI(display, cpu_transcoder), 0);
+}
+
 static void
 intel_vrr_cmrr_compute_config(struct intel_crtc_state *crtc_state)
 {
@@ -342,6 +370,11 @@ void intel_vrr_set_fixed_rr_timings(const struct intel_crtc_state *crtc_state,
 	if (!intel_vrr_possible(crtc_state))
 		return;
 
+	if (crtc_state->vrr.cmrr.enable)
+		intel_vrr_enable_cmrr(crtc_state);
+	else
+		intel_vrr_disable_cmrr(crtc_state);
+
 	intel_de_write(display, TRANS_VRR_VMIN(display, transcoder),
 		       intel_vrr_fixed_rr_hw_vmin(crtc_state) - 1);
 	intel_de_write(display, TRANS_VRR_VMAX(display, transcoder),
@@ -653,17 +686,6 @@ void intel_vrr_set_transcoder_timings(const struct intel_crtc_state *crtc_state)
 		return;
 	}
 
-	if (crtc_state->vrr.cmrr.enable) {
-		intel_de_write(display, TRANS_CMRR_M_HI(display, cpu_transcoder),
-			       upper_32_bits(crtc_state->vrr.cmrr.cmrr_m));
-		intel_de_write(display, TRANS_CMRR_M_LO(display, cpu_transcoder),
-			       lower_32_bits(crtc_state->vrr.cmrr.cmrr_m));
-		intel_de_write(display, TRANS_CMRR_N_HI(display, cpu_transcoder),
-			       upper_32_bits(crtc_state->vrr.cmrr.cmrr_n));
-		intel_de_write(display, TRANS_CMRR_N_LO(display, cpu_transcoder),
-			       lower_32_bits(crtc_state->vrr.cmrr.cmrr_n));
-	}
-
 	intel_vrr_set_fixed_rr_timings(crtc_state, cpu_transcoder);
 	intel_cmtg_set_vrr_timings(crtc_state);
 
@@ -929,8 +951,7 @@ intel_vrr_disable_dc_balancing(const struct intel_crtc_state *old_crtc_state)
 	intel_de_write(display, TRANS_VRR_CTL(display, cpu_transcoder), vrr_ctl);
 }
 
-static void intel_vrr_tg_enable(const struct intel_crtc_state *crtc_state,
-				bool cmrr_enable)
+static void intel_vrr_tg_enable(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_display *display = to_intel_display(crtc_state);
 	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
@@ -942,11 +963,12 @@ static void intel_vrr_tg_enable(const struct intel_crtc_state *crtc_state,
 	vrr_ctl = VRR_CTL_VRR_ENABLE | trans_vrr_ctl(crtc_state);
 
 	/*
-	 * FIXME this might be broken as bspec seems to imply that
-	 * even VRR_CTL_CMRR_ENABLE is armed by TRANS_CMRR_N_HI
-	 * when enabling CMRR (but not when disabling CMRR?).
+	 * This full TRANS_VRR_CTL write is the authoritative one, so it must
+	 * carry VRR_CTL_CMRR_ENABLE when CMRR is in use. Writing TRANS_CMRR_N_HI
+	 * arms the bit in hardware, but this later write would otherwise clear
+	 * it again.
 	 */
-	if (cmrr_enable)
+	if (crtc_state->vrr.cmrr.enable)
 		vrr_ctl |= VRR_CTL_CMRR_ENABLE;
 
 	intel_de_write(display, TRANS_VRR_CTL(display, cpu_transcoder), vrr_ctl);
@@ -982,7 +1004,7 @@ void intel_vrr_enable(const struct intel_crtc_state *crtc_state)
 	intel_vrr_enable_dc_balancing(crtc_state);
 
 	if (!intel_vrr_always_use_vrr_tg(display))
-		intel_vrr_tg_enable(crtc_state, crtc_state->vrr.cmrr.enable);
+		intel_vrr_tg_enable(crtc_state);
 }
 
 void intel_vrr_disable(const struct intel_crtc_state *old_crtc_state)
@@ -1009,7 +1031,7 @@ void intel_vrr_transcoder_enable(const struct intel_crtc_state *crtc_state)
 		return;
 
 	if (intel_vrr_always_use_vrr_tg(display))
-		intel_vrr_tg_enable(crtc_state, false);
+		intel_vrr_tg_enable(crtc_state);
 }
 
 void intel_vrr_transcoder_disable(const struct intel_crtc_state *old_crtc_state)
-- 
2.48.1