Re: [PATCH 14/15] drm/i915/panel: Refactor helper to get highest fixed mode

[Nautiyal, Ankit K]

On 9/11/2025 8:07 PM, Ville Syrjälä wrote:
On Thu, Sep 11, 2025 at 08:15:53AM +0530, Ankit Nautiyal wrote:
Refactor intel_panel_highest_mode() to return the fixed mode with the
highest pixel clock, removing the fallback to the adjusted mode. This makes
the function semantics clearer and better suited for future use cases where
fallback is not desirable.

Update the caller in intel_dp_mode_clock() to handle the NULL case
explicitly by falling back to the adjusted mode's crtc_clock. This also
addresses the existing FIXME comment about ambiguity between clock and
crtc_clock, by using mode->clock for fixed modes and mode->crtc_clock for
adjusted modes.

v2: Avoid introducing a new function and refactor existing one instead.
(Jani).

Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.gol...@intel.com>
---
  drivers/gpu/drm/i915/display/intel_dp.c    | 14 +++++++++-----
  drivers/gpu/drm/i915/display/intel_panel.c | 11 +++++------
  drivers/gpu/drm/i915/display/intel_panel.h |  3 +--
  3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c 
b/drivers/gpu/drm/i915/display/intel_dp.c
index 83c46e4680b3..f74ac98062d4 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1760,11 +1760,15 @@ static int intel_dp_mode_clock(const struct 
intel_crtc_state *crtc_state,
        struct intel_connector *connector = 
to_intel_connector(conn_state->connector);
        const struct drm_display_mode *adjusted_mode = 
&crtc_state->hw.adjusted_mode;
  
-	/* FIXME a bit of a mess wrt clock vs. crtc_clock */
-       if (has_seamless_m_n(connector))
-               return intel_panel_highest_mode(connector, 
adjusted_mode)->clock;
-       else
-               return adjusted_mode->crtc_clock;
+       if (has_seamless_m_n(connector)) {
+               const struct drm_display_mode *highest_mode;
+
+               highest_mode = intel_panel_highest_mode(connector);
+               if (highest_mode)
+                       return highest_mode->clock;
+       }
+
+       return adjusted_mode->crtc_clock;
  }
  
  /* Optimize link config in order: max bpp, min clock, min lanes */
diff --git a/drivers/gpu/drm/i915/display/intel_panel.c 
b/drivers/gpu/drm/i915/display/intel_panel.c
index 2a20aaaaac39..ac0f04073ecb 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -144,18 +144,17 @@ intel_panel_downclock_mode(struct intel_connector 
*connector,
  }
  
  const struct drm_display_mode *
-intel_panel_highest_mode(struct intel_connector *connector,
-                        const struct drm_display_mode *adjusted_mode)
+intel_panel_highest_mode(struct intel_connector *connector)
  {
-       const struct drm_display_mode *fixed_mode, *best_mode = adjusted_mode;
+       const struct drm_display_mode *fixed_mode, *highest_mode = NULL;
  
  	/* pick the fixed_mode that has the highest clock */
        list_for_each_entry(fixed_mode, &connector->panel.fixed_modes, head) {
-               if (fixed_mode->clock > best_mode->clock)
-                       best_mode = fixed_mode;
+               if (!highest_mode || fixed_mode->clock > highest_mode->clock)
+                       highest_mode = fixed_mode;
This looks broken now as it will always return some kind of mode
from the list, but whether or not it's better than the adjusted_mode
is no logner guaranteed.


This was in relation to supporting seamless MN DRRS with VRR timing 
generator.
As mentioned in the response to the following patch, this is not 
required and I will drop this patch from the series.

Regards,
Ankit


        }
  
-	return best_mode;
+       return highest_mode;
  }
  
  int intel_panel_get_modes(struct intel_connector *connector)
diff --git a/drivers/gpu/drm/i915/display/intel_panel.h 
b/drivers/gpu/drm/i915/display/intel_panel.h
index 56a6412cf0fb..8a17600e46a3 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.h
+++ b/drivers/gpu/drm/i915/display/intel_panel.h
@@ -37,8 +37,7 @@ const struct drm_display_mode *
  intel_panel_downclock_mode(struct intel_connector *connector,
                           const struct drm_display_mode *adjusted_mode);
  const struct drm_display_mode *
-intel_panel_highest_mode(struct intel_connector *connector,
-                        const struct drm_display_mode *adjusted_mode);
+intel_panel_highest_mode(struct intel_connector *connector);
  int intel_panel_get_modes(struct intel_connector *connector);
  enum drrs_type intel_panel_drrs_type(struct intel_connector *connector);
  enum drm_mode_status
--
2.45.2