Re: [RESEND, 09/22] drm/i915/vrr: Increment DC balance flip count on every flip

[Nautiyal, Ankit K]

On 11/3/2025 10:59 AM, Mitul Golani wrote:
Increment DC Balance Flip count before every send push to indicate
DMC firmware about new flip occurrence. This is tracked separately
from legacy FLIP_COUNT register.

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.gol...@intel.com>
---
  drivers/gpu/drm/i915/display/intel_color.c   |  1 +
  drivers/gpu/drm/i915/display/intel_display.c |  1 +
  drivers/gpu/drm/i915/display/intel_vrr.c     | 15 +++++++++++++++
  drivers/gpu/drm/i915/display/intel_vrr.h     |  3 +++
  4 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_color.c 
b/drivers/gpu/drm/i915/display/intel_color.c
index 1e97020e7304..47a732ae2448 100644
--- a/drivers/gpu/drm/i915/display/intel_color.c
+++ b/drivers/gpu/drm/i915/display/intel_color.c
@@ -2012,6 +2012,7 @@ void intel_color_prepare_commit(struct intel_atomic_state 
*state,
        display->funcs.color->load_luts(crtc_state);
  
  	if (crtc_state->use_dsb && intel_color_uses_chained_dsb(crtc_state)) {
+               intel_vrr_dcb_increment_flip_count(crtc_state, crtc);
                intel_vrr_send_push(crtc_state->dsb_color, crtc_state);
                intel_dsb_wait_for_delayed_vblank(state, crtc_state->dsb_color);
                intel_vrr_check_push_sent(crtc_state->dsb_color, crtc_state);
diff --git a/drivers/gpu/drm/i915/display/intel_display.c 
b/drivers/gpu/drm/i915/display/intel_display.c
index a00625f882e8..1a3e7a6e4ab7 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -7366,6 +7366,7 @@ static void intel_atomic_dsb_finish(struct 
intel_atomic_state *state,
        if (new_crtc_state->use_dsb && 
!intel_color_uses_chained_dsb(new_crtc_state)) {
                intel_dsb_wait_vblanks(new_crtc_state->dsb_commit, 1);
  
+		intel_vrr_dcb_increment_flip_count(new_crtc_state, crtc);

Shouldn't these have DSB context? We are asking DSB to write these 
registers.

We need to increment flip_count after  intel_vrr_send_push() not before 
as per the spec.

Also we need to do this for MMIO path along with the DSB path.

So IMO, add this flip count increment at last in intel_update_crtc() 
instead, then we do not need to use DSB.


Regards,

Ankit



                intel_vrr_send_push(new_crtc_state->dsb_commit, new_crtc_state);
                intel_dsb_wait_for_delayed_vblank(state, 
new_crtc_state->dsb_commit);
                intel_vrr_check_push_sent(new_crtc_state->dsb_commit,
diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c 
b/drivers/gpu/drm/i915/display/intel_vrr.c
index 2948abc90c69..87bd722aa32d 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.c
+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
@@ -14,6 +14,7 @@
  #include "intel_psr.h"
  #include "intel_vrr.h"
  #include "intel_vrr_regs.h"
+#include "intel_dmc_regs.h"
  #include "skl_prefill.h"
  #include "skl_watermark.h"
  
@@ -612,6 +613,20 @@ void intel_vrr_set_transcoder_timings(const struct intel_crtc_state *crtc_state)
                               EMP_AS_SDP_DB_TL(crtc_state->vrr.vsync_start));
  }
  
+void
+intel_vrr_dcb_increment_flip_count(struct intel_crtc_state *crtc_state,
+                                  struct intel_crtc *crtc)
+{
+       struct intel_display *display = to_intel_display(crtc_state);
+       enum pipe pipe = crtc->pipe;
+
+       if (!crtc_state->vrr.dc_balance.enable)
+               return;
+
+       intel_de_write(display, PIPEDMC_DCB_FLIP_COUNT(pipe),
+                      ++crtc->dc_balance.flip_count);



+}
+
  void intel_vrr_send_push(struct intel_dsb *dsb,
                         const struct intel_crtc_state *crtc_state)
  {
diff --git a/drivers/gpu/drm/i915/display/intel_vrr.h 
b/drivers/gpu/drm/i915/display/intel_vrr.h
index 66fb9ad846f2..eebc7be309db 100644
--- a/drivers/gpu/drm/i915/display/intel_vrr.h
+++ b/drivers/gpu/drm/i915/display/intel_vrr.h
@@ -14,6 +14,7 @@ struct intel_connector;
  struct intel_crtc_state;
  struct intel_dsb;
  struct intel_display;
+struct intel_crtc;
  
  bool intel_vrr_is_capable(struct intel_connector *connector);
  bool intel_vrr_is_in_range(struct intel_connector *connector, int vrefresh);
@@ -39,6 +40,8 @@ bool intel_vrr_is_fixed_rr(const struct intel_crtc_state 
*crtc_state);
  void intel_vrr_transcoder_enable(const struct intel_crtc_state *crtc_state);
  void intel_vrr_transcoder_disable(const struct intel_crtc_state *crtc_state);
  void intel_vrr_set_fixed_rr_timings(const struct intel_crtc_state 
*crtc_state);
+void intel_vrr_dcb_increment_flip_count(struct intel_crtc_state *crtc_state,
+                                       struct intel_crtc *crtc);
  bool intel_vrr_always_use_vrr_tg(struct intel_display *display);
  int intel_vrr_safe_window_start(const struct intel_crtc_state *crtc_state);
  int intel_vrr_vmin_safe_window_end(const struct intel_crtc_state *crtc_state);