diff options
| -rw-r--r-- | drivers/gpu/drm/i915/intel_dp.c | 26 |
1 files changed, 21 insertions, 5 deletions
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 74c835272292..ffe98ad9b640 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -184,9 +184,25 @@ intel_dp_link_clock(uint8_t link_bw) return 162000; } -/* I think this is a fiction */ +/* + * The units on the numbers in the next two are... bizarre. Examples will + * make it clearer; this one parallels an example in the eDP spec. + * + * intel_dp_max_data_rate for one lane of 2.7GHz evaluates as: + * + * 270000 * 1 * 8 / 10 == 216000 + * + * The actual data capacity of that configuration is 2.16Gbit/s, so the + * units are decakilobits. ->clock in a drm_display_mode is in kilohertz - + * or equivalently, kilopixels per second - so for 1680x1050R it'd be + * 119000. At 18bpp that's 2142000 kilobits per second. + * + * Thus the strange-looking division by 10 in intel_dp_link_required, to + * get the result in decakilobits instead of kilobits. + */ + static int -intel_dp_link_required(struct drm_device *dev, struct intel_dp *intel_dp, int pixel_clock) +intel_dp_link_required(struct intel_dp *intel_dp, int pixel_clock) { struct drm_crtc *crtc = intel_dp->base.base.crtc; struct intel_crtc *intel_crtc = to_intel_crtc(crtc); @@ -195,7 +211,7 @@ intel_dp_link_required(struct drm_device *dev, struct intel_dp *intel_dp, int pi if (intel_crtc) bpp = intel_crtc->bpp; - return (pixel_clock * bpp + 7) / 8; + return (pixel_clock * bpp + 9) / 10; } static int @@ -223,7 +239,7 @@ intel_dp_mode_valid(struct drm_connector *connector, /* only refuse the mode on non eDP since we have seen some weird eDP panels which are outside spec tolerances but somehow work by magic */ if (!is_edp(intel_dp) && - (intel_dp_link_required(connector->dev, intel_dp, mode->clock) + (intel_dp_link_required(intel_dp, mode->clock) > intel_dp_max_data_rate(max_link_clock, max_lanes))) return MODE_CLOCK_HIGH; @@ -670,7 +686,7 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode, 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(encoder->dev, intel_dp, mode->clock) + if (intel_dp_link_required(intel_dp, mode->clock) <= link_avail) { intel_dp->link_bw = bws[clock]; intel_dp->lane_count = lane_count; |