Re: [PATCH] drm/i915/tc: Disable outputs instead of modesetting them on link reset

[Imre Deak <imre.deak@intel.com>]

On Fri, Jun 05, 2026 at 11:28:37PM +0200, Alexander Kaplan wrote:
> After a DP-alt sink is disconnected with the link still active,
> intel_tc_port_link_reset_work() tries to recover the link via a
> modeset, flagging the active CRTCs with connectors_changed in
> reset_link_commit(). By that point intel_dp_detect() has already
> reset the sink capabilities (EDID, dfp.*, DSC DPCD - see the FIXME in
> intel_dp_detect()), so the recovery modeset is computed without them.
> Depending on which capabilities the connected mode requires, this
> either fails the atomic check with -EINVAL, triggering the WARN in
> intel_tc_port_link_reset_work():
> 
>   i915 0000:00:02.0: [drm] drm_WARN_ON(ret)
>   WARNING: ... at drivers/gpu/drm/i915/display/intel_tc.c:1838
>            intel_tc_port_link_reset_work+0x38c/0x420
> 
> or commits a configuration the disconnected link can't sustain: link
> training fails and the output is left enabled on the disconnected
> port. Either way the output stays enabled, keeping the TC PHY
> ownership held and the TC mode locked. AUX transfers then get
> rejected based on intel_digital_port_connected_locked(), so detecting
> a newly connected sink keeps failing as well: the port can't be
> recovered without disabling the output by some other means (in
> practice a reboot).
> 
> Disable the affected outputs instead of modesetting them, matching
> how commit c598c335da42 ("drm/i915/tc: Reset TypeC PHYs left enabled
> in DP-alt mode after the sink disconnects") handles the equivalent
> situation during boot/resume sanitization, for the same reason. The
> disable also releases the PHY ownership synchronously - via the
> encoder's post-PLL-disable hook - avoiding the IOM/TCSS firmware
> timeout the above commit worked around, and unblocking the HPD status
> updates of other TypeC ports. The output gets re-enabled via the
> normal hotplug flow once a sink is connected again.
> 
> Preserving the sink capabilities across the disconnect instead (the
> direction proposed for the DSC caps in the gitlab reports below)
> would avoid the -EINVAL, but not the second failure mode: the
> recovery modeset would still be committed against a dead link,
> leaving the enabled output behind after a failed link training.
> Disabling the output covers both.
> 
> Observed on PTL with a DP-alt -> HDMI 2.1 PCON adapter on a TV power
> cycle (both failure modes above); reports with the matching WARN on
> ADL and MTL in the links below.

The driver cannot disable an output that userspace has enabled. The TC
port reset above should also result in a hotplug notification, which
userspace should handle reconfiguring and re-enabling the output as
needed. Could you please provide a dmesg log on the first Link: ticket
below with the rebased

https://gitlab.freedesktop.org/-/project/4519/uploads/326fe332d4e847b29c1f38907be171df/0001-drm-i915-dp-Fix-resetting-DSC-capability-during-dete.patch

applied on the lastest drm-tip kernel, booting with drm.debug=0x15e and
reproducing the problem you still observe (also mentioning the
reproducation steps)?

Thanks.

> Fixes: c598c335da42 ("drm/i915/tc: Reset TypeC PHYs left enabled in DP-alt mode after the sink disconnects")
> Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14807
> Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11551
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Alexander Kaplan <alexander.kaplan@sms-medipool.de>
> ---
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index a21dd4e3fe4c..ae9da59ca8e3 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -5,6 +5,7 @@
> 
>  #include <linux/iopoll.h>
> 
> +#include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_print.h>
> 
>  #include "intel_atomic.h"
> @@ -1764,9 +1765,13 @@ static int reset_link_commit(struct intel_tc_port *tc,
>  	struct intel_display *display = to_intel_display(tc->dig_port);
>  	struct intel_digital_port *dig_port = tc->dig_port;
>  	struct intel_dp *intel_dp = enc_to_intel_dp(&dig_port->base);
> +	struct drm_connector_state *conn_state;
> +	struct drm_connector *connector;
> +	struct drm_plane_state *plane_state;
> +	struct drm_plane *plane;
>  	struct intel_crtc *crtc;
>  	u8 pipe_mask;
> -	int ret;
> +	int i, ret;
> 
>  	ret = drm_modeset_lock(&display->drm->mode_config.connection_mutex, ctx);
>  	if (ret)
> @@ -1779,6 +1784,13 @@ static int reset_link_commit(struct intel_tc_port *tc,
>  	if (!pipe_mask)
>  		return 0;
> 
> +	/*
> +	 * The sink is gone, so intel_dp_detect() has already reset the sink
> +	 * capabilities, and recomputing the config for the still active mode
> +	 * would fail (see the FIXME in intel_dp_detect()). Disable the
> +	 * outputs instead; the next sink connect re-enables them via the
> +	 * normal hotplug flow.
> +	 */
>  	for_each_intel_crtc_in_pipe_mask(display, crtc, pipe_mask) {
>  		struct intel_crtc_state *crtc_state;
> 
> @@ -1786,7 +1798,33 @@ static int reset_link_commit(struct intel_tc_port *tc,
>  		if (IS_ERR(crtc_state))
>  			return PTR_ERR(crtc_state);
> 
> -		crtc_state->uapi.connectors_changed = true;
> +		crtc_state->uapi.active = false;
> +
> +		ret = drm_atomic_set_mode_prop_for_crtc(&crtc_state->uapi, NULL);
> +		if (ret)
> +			return ret;
> +
> +		ret = drm_atomic_add_affected_planes(&state->base, &crtc->base);
> +		if (ret)
> +			return ret;
> +
> +		ret = drm_atomic_add_affected_connectors(&state->base, &crtc->base);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	for_each_new_connector_in_state(&state->base, connector, conn_state, i) {
> +		ret = drm_atomic_set_crtc_for_connector(conn_state, NULL);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	for_each_new_plane_in_state(&state->base, plane, plane_state, i) {
> +		ret = drm_atomic_set_crtc_for_plane(plane_state, NULL);
> +		if (ret)
> +			return ret;
> +
> +		drm_atomic_set_fb_for_plane(plane_state, NULL);
>  	}
> 
>  	if (!__intel_tc_port_link_needs_reset(tc))
>