[PATCH xf86-video-amdgpu] modesetting: re-set the crtc's mode when link-status goes BAD

[Harry Wentland]

On 2017-08-22 05:48 AM, Michel Dänzer wrote:
> From: Martin Peres <martin.peres at 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 ]
> (Ported from radeon commit 0472a605e0ec8fec1892bbc3a84698b7ef9c5296)
> 
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

Thanks, and
Acked-by: Harry Wentland <harry.wentland at amd.com>

I'll send an amd/display kernel patch soon to set link-status to bad.

Harry

> ---
>  configure.ac          |  2 +-
>  src/drmmode_display.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/configure.ac b/configure.ac
> index 0ff2bdfaa..6d7cee476 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 >= 2.4.72])
> +PKG_CHECK_MODULES(LIBDRM, [libdrm >= 2.4.78])
>  PKG_CHECK_MODULES(LIBDRM_AMDGPU, [libdrm_amdgpu >= 2.4.72])
>  PKG_CHECK_MODULES(GBM, [gbm])
>  
> diff --git a/src/drmmode_display.c b/src/drmmode_display.c
> index ad3325be6..17efde8e8 100644
> --- a/src/drmmode_display.c
> +++ b/src/drmmode_display.c
> @@ -2627,6 +2627,49 @@ amdgpu_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(pAMDGPUEnt->fd, con_id);
> +		for (j = 0; koutput && j < koutput->count_props; j++) {
> +			drmModePropertyPtr props;
> +			props = drmModeGetProperty(pAMDGPUEnt->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(pAMDGPUEnt->fd);
>  	if (!mode_res)
>  		goto out;
>