On Thu, Jan 26, 2017 at 02:37:28PM +0200, Martin Peres wrote: > Despite all the careful planing 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. > > When available, we should use the link-status information to reset > the wanted mode. > > Signed-off-by: Martin Peres <martin.peres@xxxxxxxxxxxxxxx> > --- > > WARNING: The patches have not been merged in the kernel yet, so this patch is > merely an RFC. That's how it's supposed to happen, before we can merge the kernel side, we need acceptance (=reviewed) by the userspace side. Which is why this patch here. -Daniel > > This patch is the result of discussions happening mostly in DRI-devel and > Intel-GFX on how to handle link training failures. I would advise reading the > thread [0] first and then this thread [1] which explain in great length why this > is needed and why the selected approach seems to be the best. > > The relevant kernel patches + this patch are enough to pass the relevant > DisplayPort compliance tests, provided that the Desktop Environment or another > program ([2]?) provides the initial modesetting on hotplug. > > Would this patch be acceptable to you? Any comments or suggestions? > > [0] https://lists.freedesktop.org/archives/dri-devel/2016-November/123366.html > [1] https://lists.freedesktop.org/archives/dri-devel/2016-November/124736.html > [2] https://cgit.freedesktop.org/~mperes/auto-randr/ > > > hw/xfree86/drivers/modesetting/drmmode_display.c | 51 ++++++++++++++++++++++++ > 1 file changed, 51 insertions(+) > > diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c b/hw/xfree86/drivers/modesetting/drmmode_display.c > index 6e755e9482..3144620c67 100644 > --- a/hw/xfree86/drivers/modesetting/drmmode_display.c > +++ b/hw/xfree86/drivers/modesetting/drmmode_display.c > @@ -2262,6 +2262,10 @@ drmmode_setup_colormap(ScreenPtr pScreen, ScrnInfoPtr pScrn) > } > > #ifdef CONFIG_UDEV_KMS > + > +#define DRM_MODE_LINK_STATUS_GOOD 0 > +#define DRM_MODE_LINK_STATUS_BAD 1 > + > static void > drmmode_handle_uevents(int fd, void *closure) > { > @@ -2281,6 +2285,49 @@ drmmode_handle_uevents(int fd, void *closure) > if (!found) > return; > > + /* 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(drmmode->fd, con_id); > + for (j = 0; koutput && j < koutput->count_props; j++) { > + drmModePropertyPtr props; > + props = drmModeGetProperty(drmmode->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(drmmode->fd); > if (!mode_res) > goto out; > @@ -2345,6 +2392,10 @@ out_free_res: > out: > RRGetInfo(xf86ScrnToScreen(scrn), TRUE); > } > + > +#undef DRM_MODE_LINK_STATUS_BAD > +#undef DRM_MODE_LINK_STATUS_GOOD > + > #endif > > void > -- > 2.11.0 > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
