The line time can be programmed according to the number of horizontal
pixels vs effective pixel rate ratio.

v2: improve comment as per Chris Wilson suggestion

Signed-off-by: Eugeni Dodonov <eugeni.dodo...@intel.com>
---
 drivers/gpu/drm/i915/intel_display.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index b2dc1eb..72f2211 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6103,6 +6103,19 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
                   (adjusted_mode->crtc_vsync_start - 1) |
                   ((adjusted_mode->crtc_vsync_end - 1) << 16));
 
+       if (IS_HASWELL(dev)) {
+               temp = I915_READ(PIPE_WM_LINETIME(pipe));
+               temp &= ~PIPE_WM_LINETIME_MASK;
+
+               /* The WM are computed with base on how long it takes to fill a 
single
+                * row at the given clock rate
+                * */
+               temp |= PIPE_WM_LINETIME_TIME(
+                               adjusted_mode->crtc_hdisplay /
+                               (adjusted_mode->clock / 1000));
+               I915_WRITE(PIPE_WM_LINETIME(pipe), temp);
+       }
+
        /* pipesrc controls the size that is scaled from, which should
         * always be the user's requested size.
         */
-- 
1.7.9.5

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