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drm/i915: Simplify scanline_offset handling for gen2

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Currently intel_crtc_scanline_offset() is careful to always
return a positive offset. That is not actually necessary
as long as we take care of negative values when applying the
offset in __intel_get_crtc_scanline().

This simplifies intel_crtc_scanline_offset(), and makes
the scanline_offfset arithmetic more symmetric between
the forward (__intel_get_crtc_scanline()) and reverse
(intel_crtc_scanline_to_hw()) directions.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240528185647.7765-5-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
Ville Syrjälä
2024-05-28 21:56:44 +03:00
parent 9677dd01ca
commit 5316dd0d61
1 changed files with 3 additions and 5 deletions
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8
drivers/gpu/drm/i915/display/intel_vblank.c
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@@ -240,7 +240,7 @@ static int __intel_get_crtc_scanline(struct intel_crtc *crtc)
* See update_scanline_offset() for the details on the
* scanline_offset adjustment.
*/
return (position + crtc->scanline_offset) % vtotal;
return (position + vtotal + crtc->scanline_offset) % vtotal;
}
int intel_crtc_scanline_to_hw(struct intel_crtc *crtc, int scanline)
@@ -470,7 +470,6 @@ void intel_wait_for_pipe_scanline_moving(struct intel_crtc *crtc)
static int intel_crtc_scanline_offset(const struct intel_crtc_state *crtc_state)
{
struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
/*
* The scanline counter increments at the leading edge of hsync.
@@ -482,8 +481,7 @@ static int intel_crtc_scanline_offset(const struct intel_crtc_state *crtc_state)
* last active line), the scanline counter will read vblank_start-1.
*
* On gen2 the scanline counter starts counting from 1 instead
* of vtotal-1, so we have to subtract one (or rather add vtotal-1
* to keep the value positive), instead of adding one.
* of vtotal-1, so we have to subtract one.
*
* On HSW+ the behaviour of the scanline counter depends on the output
* type. For DP ports it behaves like most other platforms, but on HDMI
@@ -500,7 +498,7 @@ static int intel_crtc_scanline_offset(const struct intel_crtc_state *crtc_state)
* answer that's slightly in the future.
*/
if (DISPLAY_VER(i915) == 2)
return intel_mode_vtotal(adjusted_mode) - 1;
return -1;
else if (HAS_DDI(i915) && intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI))
return 2;
else