diff options
authorMartin Peres <>2017-04-10 16:48:21 +0300
committerMichel Dänzer <>2017-08-18 14:40:19 +0900
commit0472a605e0ec8fec1892bbc3a84698b7ef9c5296 (patch)
parentd822a0f47070374ad0c1a97b559bae27724dc52a (diff)
modesetting: re-set the crtc's mode when link-status goes BAD
Despite all the careful planning of the kernel, a link may become insufficient to handle the currently-set mode. At this point, the kernel should mark this particular configuration as being broken and potentially prune the mode before setting the offending connector's link-status to BAD and send the userspace a hotplug event. This may happen right after a modeset or later on. Upon receiving a hot-plug event, we iterate through the connectors to re-apply the currently-set mode on all the connectors that have a link-status property set to BAD. The kernel may be able to get the link to work by dropping to using a lower link bpp (with the same display bpp). However, the modeset may fail if the kernel has pruned the mode, so to make users aware of this problem a warning is outputed in the logs to warn about having a potentially-black display. This patch does not modify the current behaviour of always propagating the events to the randr clients. This allows desktop environments to re-probe the connectors and select a new resolution based on the new (currated) mode list if a mode disapeared. This behaviour is expected in order to pass the Display Port compliance tests. (Ported from xserver commit bcee1b76aa0db8525b491485e90b8740763d7de6) [ Michel: Bump libdrm dependency to >= 2.4.78 for DRM_MODE_LINK_STATUS_BAD ] Reviewed-by: Alex Deucher <>
2 files changed, 44 insertions, 1 deletions
diff --git a/ b/
index c9bc0a95..170f42ef 100644
--- a/
+++ b/
@@ -70,7 +70,7 @@ XORG_DRIVER_CHECK_EXT(XV, videoproto)
XORG_DRIVER_CHECK_EXT(DPMSExtension, xextproto)
# Checks for libraries.
-PKG_CHECK_MODULES(LIBDRM, [libdrm >= 2.4.60])
+PKG_CHECK_MODULES(LIBDRM, [libdrm >= 2.4.78])
# Obtain compiler/linker options for the driver dependencies
diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index 4839b415..f926bc01 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -2826,6 +2826,49 @@ radeon_mode_hotplug(ScrnInfoPtr scrn, drmmode_ptr drmmode)
Bool changed = FALSE;
int num_dvi = 0, num_hdmi = 0;
+ /* Try to re-set the mode on all the connectors with a BAD link-state:
+ * This may happen if a link degrades and a new modeset is necessary, using
+ * different link-training parameters. If the kernel found that the current
+ * mode is not achievable anymore, it should have pruned the mode before
+ * sending the hotplug event. Try to re-set the currently-set mode to keep
+ * the display alive, this will fail if the mode has been pruned.
+ * In any case, we will send randr events for the Desktop Environment to
+ * deal with it, if it wants to.
+ */
+ for (i = 0; i < config->num_output; i++) {
+ xf86OutputPtr output = config->output[i];
+ drmmode_output_private_ptr drmmode_output = output->driver_private;
+ uint32_t con_id = drmmode_output->mode_output->connector_id;
+ drmModeConnectorPtr koutput;
+ /* Get an updated view of the properties for the current connector and
+ * look for the link-status property
+ */
+ koutput = drmModeGetConnectorCurrent(pRADEONEnt->fd, con_id);
+ for (j = 0; koutput && j < koutput->count_props; j++) {
+ drmModePropertyPtr props;
+ props = drmModeGetProperty(pRADEONEnt->fd, koutput->props[j]);
+ if (props && props->flags & DRM_MODE_PROP_ENUM &&
+ !strcmp(props->name, "link-status") &&
+ koutput->prop_values[j] == DRM_MODE_LINK_STATUS_BAD) {
+ xf86CrtcPtr crtc = output->crtc;
+ if (!crtc)
+ continue;
+ /* the connector got a link failure, re-set the current mode */
+ drmmode_set_mode_major(crtc, &crtc->mode, crtc->rotation,
+ crtc->x, crtc->y);
+ xf86DrvMsg(scrn->scrnIndex, X_WARNING,
+ "hotplug event: connector %u's link-state is BAD, "
+ "tried resetting the current mode. You may be left "
+ "with a black screen if this fails...\n", con_id);
+ }
+ drmModeFreeProperty(props);
+ }
+ drmModeFreeConnector(koutput);
+ }
mode_res = drmModeGetResources(pRADEONEnt->fd);
if (!mode_res)
goto out;