Pretty useful to debug our DP bandwidth woes.
v2: Also print out the required and available link bandwidth,
suggested by Chris Wilson.
v3: Also print out the input parameters so that diagnosing failures to
find a valid dp link configuration is possible.
Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
drivers/gpu/drm/i915/intel_dp.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 44cf32c..4b7a286 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -688,7 +688,7 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
int lane_count, clock;
int max_lane_count = intel_dp_max_lane_count(intel_dp);
int max_clock = intel_dp_max_link_bw(intel_dp) == DP_LINK_BW_2_7 ? 1 : 0;
- int bpp;
+ int bpp, mode_rate;
static int bws[2] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7 };
if (is_edp(intel_dp) && intel_dp->panel_fixed_mode) {
@@ -702,24 +702,30 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
mode->clock = intel_dp->panel_fixed_mode->clock;
}
+ DRM_DEBUG_KMS("Display port link computation with max lane count %i "
+ "max bw %02x pixel clock %iKHz\n",
+ max_lane_count, bws[max_clock], mode->clock);
+
if (!intel_dp_adjust_dithering(intel_dp, mode, adjusted_mode))
return false;
bpp = adjusted_mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24;
+ mode_rate = intel_dp_link_required(mode->clock, bpp);
for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
for (clock = 0; clock <= max_clock; clock++) {
int link_avail = intel_dp_max_data_rate(intel_dp_link_clock(bws[clock]), lane_count);
- if (intel_dp_link_required(mode->clock, bpp)
- <= link_avail) {
+ if (mode_rate <= link_avail) {
intel_dp->link_bw = bws[clock];
intel_dp->lane_count = lane_count;
adjusted_mode->clock = intel_dp_link_clock(intel_dp->link_bw);
DRM_DEBUG_KMS("Display port link bw %02x lane "
- "count %d clock %d\n",
+ "count %d clock %d bpp %d\n",
intel_dp->link_bw, intel_dp->lane_count,
- adjusted_mode->clock);
+ adjusted_mode->clock, bpp);
+ DRM_DEBUG_KMS("Display port link bw required %i available %i\n",
+ mode_rate, link_avail);
return true;
}
}
--
1.7.10
