On Mon, 14 Dec 2015, Thierry Reding thierry.reding@gmail.com wrote:
From: Thierry Reding treding@nvidia.com
This helper chooses an appropriate configuration, according to the bitrate requirements of the video mode and the capabilities of the DisplayPort sink.
Signed-off-by: Thierry Reding treding@nvidia.com
drivers/gpu/drm/drm_dp_helper.c | 55 +++++++++++++++++++++++++++++++++++++++++ include/drm/drm_dp_helper.h | 5 ++++ 2 files changed, 60 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index da519acfeba7..95825155dc89 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -512,6 +512,61 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) } EXPORT_SYMBOL(drm_dp_link_configure);
+/**
- drm_dp_link_choose() - choose the lowest possible configuration for a mode
- @link: DRM DP link object
- @mode: DRM display mode
- @info: DRM display information
- According to the eDP specification, a source should select a configuration
- with the lowest number of lanes and the lowest possible link rate that can
- match the bitrate requirements of a video mode. However it must ensure not
- to exceed the capabilities of the sink.
Eventually this would have to take into account the intersection of per-sink and per-source supported rates, including the intermediate frequencies. Until then, i915 couldn't switch over.
BR, Jani.
- Returns: 0 on success or a negative error code on failure.
- */
+int drm_dp_link_choose(struct drm_dp_link *link,
const struct drm_display_mode *mode,const struct drm_display_info *info)+{
- /* available link symbol clock rates */
- static const unsigned int rates[3] = { 162000, 270000, 540000 };
- /* available number of lanes */
- static const unsigned int lanes[3] = { 1, 2, 4 };
- unsigned long requirement, capacity;
- unsigned int rate = link->max_rate;
- unsigned int i, j;
- /* bandwidth requirement */
- requirement = mode->clock * info->bpc * 3;
- for (i = 0; i < ARRAY_SIZE(lanes) && lanes[i] <= link->max_lanes; i++) {
for (j = 0; j < ARRAY_SIZE(rates) && rates[j] <= rate; j++) {/** Capacity for this combination of lanes and rate,* factoring in the ANSI 8B/10B encoding.** Link rates in the DRM DP helpers are really link* symbol frequencies, so a tenth of the actual rate* of the link.*/capacity = lanes[i] * (rates[j] * 10) * 8 / 10;if (capacity >= requirement) {DRM_DEBUG_KMS("using %u lanes at %u kHz (%lu/%lu kbps)\n",lanes[i], rates[j], requirement,capacity);link->lanes = lanes[i];link->rate = rates[j];return 0;}}- }
- return -ERANGE;
+} +EXPORT_SYMBOL(drm_dp_link_choose);
/*
- I2C-over-AUX implementation
*/ diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 20ae0e413b64..f3eacf62add8 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -27,6 +27,8 @@ #include <linux/i2c.h> #include <linux/delay.h>
+#include <drm/drm_crtc.h>
/*
- Unless otherwise noted, all values are from the DP 1.1a spec. Note that
- DP and DPCD versions are independent. Differences from 1.0 are not noted,
@@ -832,6 +834,9 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link); +int drm_dp_link_choose(struct drm_dp_link *link,
const struct drm_display_mode *mode,const struct drm_display_info *info);int drm_dp_aux_register(struct drm_dp_aux *aux); void drm_dp_aux_unregister(struct drm_dp_aux *aux);