drm/i915: Introduce intel_scanlines_to_usecs()

Introduce intel_scanlines_to_usecs() as a counterpart to
intel_usecs_to_scanlines().

We'll have some use for this in DSB code as we want to do
relative scanline waits to evade the delayed vblank, but
unfortunately DSB can't do relative scanline waits (only
absolute). So we'll instead convert the relative scanline
count to usec and do a relative usec wait instead (which the
DSB knows how to do).

Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240930170415.23841-9-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c
index 3a28d8450a3849ed0a6f56357f4e315153fa40e8..8ed8dd5fe45844be5050abf5e75f01f534de0300 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_crtc.c
+++ b/drivers/gpu/drm/i915/display/intel_crtc.c
@@ -483,6 +483,17 @@ int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
                                1000 * adjusted_mode->crtc_htotal);
 }
 
+int intel_scanlines_to_usecs(const struct drm_display_mode *adjusted_mode,
+                            int scanlines)
+{
+       /* paranoia */
+       if (!adjusted_mode->crtc_clock)
+               return 1;
+
+       return DIV_ROUND_UP_ULL(mul_u32_u32(scanlines, adjusted_mode->crtc_htotal * 1000),
+                               adjusted_mode->crtc_clock);
+}
+
 /**
  * intel_pipe_update_start() - start update of a set of display registers
  * @state: the atomic state

diff --git a/drivers/gpu/drm/i915/display/intel_crtc.h b/drivers/gpu/drm/i915/display/intel_crtc.h
index a58ecd11bba262295a54e1a56945a07f8fa0e89f..34ffbd2ee1b796d66ad4a28b6f6f61540d7b901e 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_crtc.h
+++ b/drivers/gpu/drm/i915/display/intel_crtc.h
@@ -31,6 +31,8 @@ struct intel_display;
 
 int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
                             int usecs);
+int intel_scanlines_to_usecs(const struct drm_display_mode *adjusted_mode,
+                            int scanlines);
 void intel_crtc_arm_vblank_event(struct intel_crtc_state *crtc_state);
 u32 intel_crtc_max_vblank_count(const struct intel_crtc_state *crtc_state);
 int intel_crtc_init(struct drm_i915_private *dev_priv, enum pipe pipe);