> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-boun...@lists.freedesktop.org] On Behalf
> Of Michel Dänzer
> Sent: Friday, August 18, 2017 1:54 AM
> To: amd-gfx@lists.freedesktop.org
> Subject: [PATCH xf86-video-ati] modesetting: re-set the crtc's mode when
> link-status goes BAD
>
> From: Martin Peres <martin.pe...@linux.intel.com>
>
> 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 ]
>
> Signed-off-by: Michel Dänzer <michel.daen...@amd.com>
Reviewed-by: Alex Deucher <alexander.deuc...@amd.com>
> ---
> configure.ac | 2 +-
> src/drmmode_display.c | 43
> +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/configure.ac b/configure.ac
> index c9bc0a958..170f42ef7 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -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])
> PKG_CHECK_MODULES(LIBDRM_RADEON, [libdrm_radeon])
>
> # Obtain compiler/linker options for the driver dependencies
> diff --git a/src/drmmode_display.c b/src/drmmode_display.c
> index 4839b415c..f926bc018 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;
> --
> 2.14.1
>
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