Compute Fixed Average Vtotal/CMRR with resepect to
userspace VRR enablement. Also calculate required
parameters in case of CMRR is  enabled. During
intel_vrr_compute_config, CMRR is getting enabled
based on userspace has enabled Adaptive Sync Vtotal
mode (Legacy VRR) or not.

--v2:
- Update is_cmrr_frac_required function return as bool, not int. [Jani]
- Use signed int math instead of unsigned in cmrr_get_vtotal2. [Jani]
- Fix typo and usage of camel case in cmrr_get_vtotal. [Jani]
- Use do_div in cmrr_get_vtotalwhile calculating cmrr_m. [ Jani]
- Simplify cmrr and vrr compute config in intel_vrr_compute_config. [Jani]
- Correct valiable name usage in is_cmrr_frac_required. [Ville]

--v3:
- Removing RFC tag.

--v4:
- Added edp check to address edp usecase for now. (ville)
- Updated is_cmrr_fraction_required to more simplified calculation.
- on longterm goal to be worked upon uapi as suggestion from ville.

--v5:
- Correct vtotal paramas accuracy and add 2 digit precision.
- Avoid using DIV_ROUND_UP and improve scanline precision.

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.gol...@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c  |  1 +
 .../drm/i915/display/intel_display_device.h   |  1 +
 drivers/gpu/drm/i915/display/intel_vrr.c      | 86 +++++++++++++++++--
 3 files changed, 82 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c 
b/drivers/gpu/drm/i915/display/intel_display.c
index e7382d2855ba..ddcfa52d0a38 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -5367,6 +5367,7 @@ intel_pipe_config_compare(const struct intel_crtc_state 
*current_config,
                PIPE_CONF_CHECK_I(vrr.guardband);
                PIPE_CONF_CHECK_LLI(cmrr.cmrr_m);
                PIPE_CONF_CHECK_LLI(cmrr.cmrr_n);
+               PIPE_CONF_CHECK_BOOL(cmrr.enable);
        }
 
 #undef PIPE_CONF_CHECK_X
diff --git a/drivers/gpu/drm/i915/display/intel_display_device.h 
b/drivers/gpu/drm/i915/display/intel_display_device.h
index 79e9f1c3e241..07808426a3b5 100644
--- a/drivers/gpu/drm/i915/display/intel_display_device.h
+++ b/drivers/gpu/drm/i915/display/intel_display_device.h
@@ -68,6 +68,7 @@ struct drm_printer;
 #define HAS_TRANSCODER(i915, trans)    
((DISPLAY_RUNTIME_INFO(i915)->cpu_transcoder_mask & \
                                          BIT(trans)) != 0)
 #define HAS_VRR(i915)                  (DISPLAY_VER(i915) >= 11)
+#define HAS_CMRR(i915)                 (DISPLAY_VER(i915) >= 20)
 #define INTEL_NUM_PIPES(i915)          
(hweight8(DISPLAY_RUNTIME_INFO(i915)->pipe_mask))
 #define I915_HAS_HOTPLUG(i915)         (DISPLAY_INFO(i915)->has_hotplug)
 #define OVERLAY_NEEDS_PHYSICAL(i915)   
(DISPLAY_INFO(i915)->overlay_needs_physical)
diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c 
b/drivers/gpu/drm/i915/display/intel_vrr.c
index 8f1d241e1f79..67a419938cbb 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -9,6 +9,10 @@
 #include "intel_de.h"
 #include "intel_display_types.h"
 #include "intel_vrr.h"
+#include "intel_dp.h"
+
+#define FIXED_POINT_PRECISION          100
+#define CMRR_PRECISION_TOLERANCE       10
 
 bool intel_vrr_is_capable(struct intel_connector *connector)
 {
@@ -105,6 +109,57 @@ int intel_vrr_vmax_vblank_start(const struct 
intel_crtc_state *crtc_state)
        return crtc_state->vrr.vmax - intel_vrr_vblank_exit_length(crtc_state);
 }
 
+static bool
+is_cmrr_frac_required(struct intel_crtc_state *crtc_state)
+{
+       int calculated_refresh_k, actual_refresh_k, pixel_clock_per_line;
+       struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+
+       actual_refresh_k =
+               drm_mode_vrefresh(adjusted_mode) * FIXED_POINT_PRECISION;
+       pixel_clock_per_line =
+               adjusted_mode->crtc_clock * 1000 / adjusted_mode->crtc_htotal;
+       calculated_refresh_k =
+               pixel_clock_per_line * FIXED_POINT_PRECISION / 
adjusted_mode->crtc_vtotal;
+
+       if ((actual_refresh_k - calculated_refresh_k) < 
CMRR_PRECISION_TOLERANCE)
+               return false;
+
+       return true;
+}
+
+static unsigned int
+cmrr_get_vtotal(struct intel_crtc_state *crtc_state)
+{
+       int multiplier_m = 1, multiplier_n = 1, vtotal;
+       int actual_refresh_rate, desired_refresh_rate;
+       long long actual_pixel_rate, adjusted_pixel_rate, pixel_clock_per_line;
+       struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+
+       pixel_clock_per_line =
+               adjusted_mode->crtc_clock * 1000 / adjusted_mode->crtc_htotal;
+       actual_refresh_rate =
+               pixel_clock_per_line * FIXED_POINT_PRECISION / 
adjusted_mode->crtc_vtotal;
+       desired_refresh_rate = drm_mode_vrefresh(adjusted_mode);
+       actual_pixel_rate = actual_refresh_rate * adjusted_mode->crtc_vtotal;
+       actual_pixel_rate =
+               (actual_pixel_rate * adjusted_mode->crtc_htotal) / 
FIXED_POINT_PRECISION;
+
+       if (is_cmrr_frac_required(crtc_state)) {
+               multiplier_m = 1001;
+               multiplier_n = 1000;
+       }
+
+       crtc_state->cmrr.cmrr_n =
+               ((desired_refresh_rate * adjusted_mode->crtc_htotal * 
multiplier_n) / multiplier_m);
+       crtc_state->cmrr.cmrr_n *= multiplier_n;
+       vtotal = (actual_pixel_rate * multiplier_n) / crtc_state->cmrr.cmrr_n;
+       adjusted_pixel_rate = actual_pixel_rate * multiplier_m;
+       crtc_state->cmrr.cmrr_m = do_div(adjusted_pixel_rate, 
crtc_state->cmrr.cmrr_n);
+
+       return vtotal;
+}
+
 void
 intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
                         struct drm_connector_state *conn_state)
@@ -113,6 +168,7 @@ intel_vrr_compute_config(struct intel_crtc_state 
*crtc_state,
        struct drm_i915_private *i915 = to_i915(crtc->base.dev);
        struct intel_connector *connector =
                to_intel_connector(conn_state->connector);
+       bool is_edp = intel_dp_is_edp(intel_attached_dp(connector));
        struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
        const struct drm_display_info *info = &connector->base.display_info;
        int vmin, vmax;
@@ -149,6 +205,22 @@ intel_vrr_compute_config(struct intel_crtc_state 
*crtc_state,
 
        crtc_state->vrr.flipline = crtc_state->vrr.vmin + 1;
 
+       /*
+        * When panel is VRR capable and userspace has
+        * not enabled adaptive sync mode then Fixed Average
+        * Vtotal mode should be enabled.
+        */
+       if (crtc_state->uapi.vrr_enabled) {
+               crtc_state->vrr.enable = true;
+               crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
+       } else if (HAS_CMRR(i915) && is_edp) {
+               crtc_state->cmrr.enable = true;
+               crtc_state->vrr.vmax = cmrr_get_vtotal(crtc_state);
+               crtc_state->vrr.vmin = crtc_state->vrr.vmax;
+               crtc_state->vrr.flipline = crtc_state->vrr.vmin;
+               crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
+       }
+
        /*
         * For XE_LPD+, we use guardband and pipeline override
         * is deprecated.
@@ -161,11 +233,6 @@ intel_vrr_compute_config(struct intel_crtc_state 
*crtc_state,
                        min(255, crtc_state->vrr.vmin - 
adjusted_mode->crtc_vblank_start -
                            crtc_state->framestart_delay - 1);
        }
-
-       if (crtc_state->uapi.vrr_enabled) {
-               crtc_state->vrr.enable = true;
-               crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
-       }
 }
 
 static u32 trans_vrr_ctl(const struct intel_crtc_state *crtc_state)
@@ -292,7 +359,14 @@ void intel_vrr_get_config(struct intel_crtc_state 
*crtc_state)
 
        trans_vrr_ctl = intel_de_read(dev_priv, TRANS_VRR_CTL(cpu_transcoder));
 
-       crtc_state->vrr.enable = trans_vrr_ctl & VRR_CTL_VRR_ENABLE;
+       if (HAS_CMRR(dev_priv)) {
+               crtc_state->cmrr.enable = (trans_vrr_ctl & VRR_CTL_CMRR_ENABLE) 
&&
+                                         (trans_vrr_ctl & VRR_CTL_VRR_ENABLE);
+               crtc_state->vrr.enable = trans_vrr_ctl & VRR_CTL_VRR_ENABLE &&
+                                        !(trans_vrr_ctl & VRR_CTL_CMRR_ENABLE);
+       } else {
+               crtc_state->vrr.enable = trans_vrr_ctl & VRR_CTL_VRR_ENABLE;
+       }
 
        if (crtc_state->cmrr.enable) {
                crtc_state->cmrr.cmrr_n =
-- 
2.25.1

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