[Bug 65024] eDP can't display on Hsw-ULT in UEFI mode

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=65024

--- Comment #3 from XiongZhang <xiong.y.zhang at intel.com> ---
The issue seems relate to dp link bandwidth. If I add following patch, eDP can
display correctly.
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 3426a61..2d26f8f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -724,6 +724,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
        bpp = min_t(int, 8*3, pipe_config->pipe_bpp);
        if (is_edp(intel_dp) && dev_priv->vbt.edp_bpp)
                bpp = min_t(int, bpp, dev_priv->vbt.edp_bpp);
+
+       bpp = 24;

        for (; bpp >= 6*3; bpp -= 2*3) {
                mode_rate = intel_dp_link_required(target_clock, bpp);
@@ -744,6 +746,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
        return false;

 found:
+       bpp = 18;
+
        if (intel_dp->color_range_auto) {

Bios report dev_priv->vbt.edp_bpp=18.

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