* Re: [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change
2026-05-05 3:35 [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change ChunAn Wu
@ 2026-05-05 8:02 ` Jani Nikula
2026-05-05 8:34 ` Imre Deak
2026-05-06 18:55 ` Ville Syrjälä
2 siblings, 0 replies; 4+ messages in thread
From: Jani Nikula @ 2026-05-05 8:02 UTC (permalink / raw)
To: ChunAn Wu, Rodrigo Vivi, Joonas Lahtinen, Tvrtko Ursulin,
David Airlie, Simona Vetter
Cc: intel-gfx, intel-xe, dri-devel, linux-kernel
On Tue, 05 May 2026, ChunAn Wu <an.wu@canonical.com> wrote:
> When Fn+F4 triggers mirror mode, the BIOS/EC reconfigures a TC port
> mode (e.g. DP-Alt to TBT-Alt via UCSI) without generating HPD. The
> driver's cached TC mode becomes stale, so intel_dp_aux_xfer() uses
> the wrong power domain and IO routing, and AUX transactions fail.
>
> This occurs when the USB-C-to-HDMI dongle does not support TBT, so
> the mode switch creates a mismatch. It also occurs with slow monitors
> whose delayed HPD/DDC/EDID recovery causes the Type-C layer to settle
> on a stale tbt-alt state before the dongle finishes re-negotiation.
>
> Add intel_tc_port_aux_recover() to detect hardware/cached TC mode
> divergence and reset the PHY. Wrap it with
> intel_dp_aux_xfer_with_recovery() to retry with corrected settings.
>
> Tested on Panther Lake and Lunar Lake with a BenQ HDMI monitor via
> USB-C-to-HDMI dongle.
What are the changes between v1 and v2?
>
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
> drivers/gpu/drm/i915/display/intel_dp_aux.c | 41 +++++++++--
> drivers/gpu/drm/i915/display/intel_tc.c | 75 +++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_tc.h | 1 +
> 3 files changed, 113 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> index b20ec3e589fa..d496b2231656 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> @@ -481,6 +481,39 @@ static u32 intel_dp_aux_xfer_flags(const struct drm_dp_aux_msg *msg)
> return 0;
> }
>
> +/**
> + * intel_dp_aux_xfer_with_recovery - AUX transfer with TC port recovery
> + * @intel_dp: the DP port
> + * @send: buffer of bytes to send
> + * @send_bytes: number of bytes to send
> + * @recv: buffer to store received reply
> + * @recv_size: maximum number of bytes to receive
> + * @aux_send_ctl_flags: extra flags for the AUX send control register
> + *
> + * Wrapper around intel_dp_aux_xfer() that attempts to recover from an
> + * external TC port mode change (e.g., dp-alt -> tbt-alt via hotkey BIOS
> + * action) when the initial AUX transfer fails. On failure, recovery is
> + * attempted once via intel_tc_port_aux_recover() before retrying.
> + *
> + * Returns: number of received bytes on success, negative error code on failure.
> + */
> +static int
> +intel_dp_aux_xfer_with_recovery(struct intel_dp *intel_dp,
> + const u8 *send, int send_bytes,
> + u8 *recv, int recv_size,
> + u32 aux_send_ctl_flags)
> +{
> + struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> + int ret;
> +
> + ret = intel_dp_aux_xfer(intel_dp, send, send_bytes, recv, recv_size,
> + aux_send_ctl_flags);
> + if (ret < 0 && intel_tc_port_aux_recover(dig_port))
> + ret = intel_dp_aux_xfer(intel_dp, send, send_bytes, recv,
> + recv_size, aux_send_ctl_flags);
> + return ret;
> +}
> +
> static ssize_t
> intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> {
> @@ -508,8 +541,8 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> if (msg->buffer)
> memcpy(txbuf + HEADER_SIZE, msg->buffer, msg->size);
>
> - ret = intel_dp_aux_xfer(intel_dp, txbuf, txsize,
> - rxbuf, rxsize, flags);
> + ret = intel_dp_aux_xfer_with_recovery(intel_dp, txbuf, txsize,
> + rxbuf, rxsize, flags);
> if (ret > 0) {
> msg->reply = rxbuf[0] >> 4;
>
> @@ -531,8 +564,8 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> if (drm_WARN_ON(display->drm, rxsize > 20))
> return -E2BIG;
>
> - ret = intel_dp_aux_xfer(intel_dp, txbuf, txsize,
> - rxbuf, rxsize, flags);
> + ret = intel_dp_aux_xfer_with_recovery(intel_dp, txbuf, txsize,
> + rxbuf, rxsize, flags);
> if (ret > 0) {
> msg->reply = rxbuf[0] >> 4;
> /*
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index a21dd4e3fe4c..1b23161e4eea 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -1861,6 +1861,81 @@ void intel_tc_port_link_cancel_reset_work(struct intel_digital_port *dig_port)
> cancel_delayed_work(&tc->link_reset_work);
> }
>
> +/**
> + * intel_tc_port_aux_recover - Recover AUX channel after external TC mode change
> + * @dig_port: digital port
> + *
> + * When firmware causes a TC port mode change (e.g., dp-alt -> disconnect ->
> + * tbt-alt) during a hotkey-triggered display mode switch, AUX transactions
> + * using the stale power domain and IO flags will fail with timeouts or errors.
> + * This happens because:
> + *
> + * 1. The display driver holds the TC link in dp-alt mode (link_refcount > 0)
> + * 2. Firmware (e.g., via HP WMI hotkey BIOS action) reconfigures the TC port
> + * mode externally without notifying the display driver
> + * 3. tc->mode stays as TC_PORT_DP_ALT while HW transitions to a different
> + * mode, invalidating the AUX power domain and IO flags used by
> + * intel_dp_aux_xfer()
> + *
> + * This function detects the discrepancy between tc->mode and actual HW state,
> + * and re-synchronizes them via a TC PHY reset. After recovery, AUX retries
> + * will use the correct power domain and control flags.
> + *
> + * The link_refcount is temporarily cleared to allow intel_tc_port_reset_mode()
> + * to proceed without the PHY-ownership assertion that fires when link_refcount
> + * is non-zero and firmware has already released PHY ownership.
> + *
> + * Must be called outside the TC port lock (tc->lock).
> + *
> + * Returns: %true if recovery was performed and AUX can be retried,
> + * %false if recovery was not needed or not possible.
> + */
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port)
> +{
> + struct intel_tc_port *tc;
> + struct intel_display *display;
> + bool recovered = false;
> +
> + if (!intel_encoder_is_tc(&dig_port->base))
> + return false;
> +
> + tc = to_tc_port(dig_port);
> + display = to_intel_display(dig_port);
> +
> + mutex_lock(&tc->lock);
> +
> + /*
> + * Recovery is only needed when the link is actively held AND the HW
> + * TC mode has diverged from the driver's cached state.
> + */
> + if (!tc->link_refcount || !intel_tc_port_needs_reset(tc))
> + goto out;
> +
> + drm_dbg_kms(display->drm,
> + "Port %s: AUX recover: external TC mode change detected (%s -> HW), reconnecting TC PHY\n",
> + tc->port_name, tc_port_mode_name(tc->mode));
> +
> + /*
> + * Temporarily clear link_refcount so intel_tc_port_reset_mode() can
> + * run the PHY disconnect/connect cycle without the ownership assertion
> + * that fires when link_refcount > 0 and firmware has already released
> + * PHY ownership externally.
> + */
> + tc->link_refcount = 0;
> + intel_tc_port_reset_mode(tc, 1, false);
> + tc->link_refcount = 1;
> +
> + recovered = tc->mode != TC_PORT_DISCONNECTED;
> + if (!recovered)
> + drm_warn(display->drm,
> + "Port %s: AUX recover: failed to restore TC port mode\n",
> + tc->port_name);
> +
> +out:
> + mutex_unlock(&tc->lock);
> + return recovered;
> +}
> +
> static void __intel_tc_port_lock(struct intel_tc_port *tc,
> int required_lanes)
> {
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.h b/drivers/gpu/drm/i915/display/intel_tc.h
> index 6719aea5bd58..d44998a3081a 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.h
> +++ b/drivers/gpu/drm/i915/display/intel_tc.h
> @@ -108,6 +108,7 @@ bool intel_tc_port_ref_held(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_needs_reset(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_reset(struct intel_digital_port *dig_port);
> void intel_tc_port_link_cancel_reset_work(struct intel_digital_port *dig_port);
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port);
>
> int intel_tc_port_init(struct intel_digital_port *dig_port, bool is_legacy);
> void intel_tc_port_cleanup(struct intel_digital_port *dig_port);
--
Jani Nikula, Intel
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change
2026-05-05 3:35 [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change ChunAn Wu
2026-05-05 8:02 ` Jani Nikula
@ 2026-05-05 8:34 ` Imre Deak
2026-05-06 18:55 ` Ville Syrjälä
2 siblings, 0 replies; 4+ messages in thread
From: Imre Deak @ 2026-05-05 8:34 UTC (permalink / raw)
To: ChunAn Wu
Cc: Jani Nikula, Rodrigo Vivi, Joonas Lahtinen, Tvrtko Ursulin,
David Airlie, Simona Vetter, intel-gfx, intel-xe, dri-devel,
linux-kernel
On Tue, May 05, 2026 at 11:35:57AM +0800, ChunAn Wu wrote:
> When Fn+F4 triggers mirror mode, the BIOS/EC reconfigures a TC port
> mode (e.g. DP-Alt to TBT-Alt via UCSI) without generating HPD. The
> driver's cached TC mode becomes stale, so intel_dp_aux_xfer() uses
> the wrong power domain and IO routing, and AUX transactions fail.
>
> This occurs when the USB-C-to-HDMI dongle does not support TBT, so
> the mode switch creates a mismatch. It also occurs with slow monitors
> whose delayed HPD/DDC/EDID recovery causes the Type-C layer to settle
> on a stale tbt-alt state before the dongle finishes re-negotiation.
>
> Add intel_tc_port_aux_recover() to detect hardware/cached TC mode
> divergence and reset the PHY. Wrap it with
> intel_dp_aux_xfer_with_recovery() to retry with corrected settings.
>
> Tested on Panther Lake and Lunar Lake with a BenQ HDMI monitor via
> USB-C-to-HDMI dongle.
>
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
>
> [...]
>
> +/**
> + * intel_tc_port_aux_recover - Recover AUX channel after external TC mode change
> + * @dig_port: digital port
> + *
> + * When firmware causes a TC port mode change (e.g., dp-alt -> disconnect ->
> + * tbt-alt) during a hotkey-triggered display mode switch, AUX transactions
> + * using the stale power domain and IO flags will fail with timeouts or errors.
> + * This happens because:
> + *
> + * 1. The display driver holds the TC link in dp-alt mode (link_refcount > 0)
> + * 2. Firmware (e.g., via HP WMI hotkey BIOS action) reconfigures the TC port
> + * mode externally without notifying the display driver
> + * 3. tc->mode stays as TC_PORT_DP_ALT while HW transitions to a different
> + * mode, invalidating the AUX power domain and IO flags used by
> + * intel_dp_aux_xfer()
> + *
> + * This function detects the discrepancy between tc->mode and actual HW state,
> + * and re-synchronizes them via a TC PHY reset. After recovery, AUX retries
> + * will use the correct power domain and control flags.
> + *
> + * The link_refcount is temporarily cleared to allow intel_tc_port_reset_mode()
> + * to proceed without the PHY-ownership assertion that fires when link_refcount
> + * is non-zero and firmware has already released PHY ownership.
> + *
> + * Must be called outside the TC port lock (tc->lock).
> + *
> + * Returns: %true if recovery was performed and AUX can be retried,
> + * %false if recovery was not needed or not possible.
> + */
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port)
> +{
> + struct intel_tc_port *tc;
> + struct intel_display *display;
> + bool recovered = false;
> +
> + if (!intel_encoder_is_tc(&dig_port->base))
> + return false;
> +
> + tc = to_tc_port(dig_port);
> + display = to_intel_display(dig_port);
> +
> + mutex_lock(&tc->lock);
> +
> + /*
> + * Recovery is only needed when the link is actively held AND the HW
> + * TC mode has diverged from the driver's cached state.
> + */
> + if (!tc->link_refcount || !intel_tc_port_needs_reset(tc))
> + goto out;
> +
> + drm_dbg_kms(display->drm,
> + "Port %s: AUX recover: external TC mode change detected (%s -> HW), reconnecting TC PHY\n",
> + tc->port_name, tc_port_mode_name(tc->mode));
> +
> + /*
> + * Temporarily clear link_refcount so intel_tc_port_reset_mode() can
> + * run the PHY disconnect/connect cycle without the ownership assertion
> + * that fires when link_refcount > 0 and firmware has already released
> + * PHY ownership externally.
> + */
> + tc->link_refcount = 0;
This looks wrong, NAK from my side:
A non-zero link_refcount guards an active output, which must maintain
the TypeC mode with which the output was enabled. So that TypeC mode
cannot be reset from under the active output as done in this patch.
The commit message fails to mention how the display driver is supposed
to notice that the user have pressed F4 and the firmware has
reconfigured things in the background. Assuming that the FW's
reconfiguration in the background is actually a valid thing to do, i.e.
doesn't result in getting the active TypeC port into a broken state, the
transition to the new TypeC mode should happen in the regular way: via
an HPD event, if neecessary using the
drm_connector_funcs::oob_hotplug_event interface, disabling any active
outputs and _then_ switching the driver's idea of the TypeC mode to
reflect the HW state.
> + intel_tc_port_reset_mode(tc, 1, false);
> + tc->link_refcount = 1;
> +
> + recovered = tc->mode != TC_PORT_DISCONNECTED;
> + if (!recovered)
> + drm_warn(display->drm,
> + "Port %s: AUX recover: failed to restore TC port mode\n",
> + tc->port_name);
> +
> +out:
> + mutex_unlock(&tc->lock);
> + return recovered;
> +}
> +
> static void __intel_tc_port_lock(struct intel_tc_port *tc,
> int required_lanes)
> {
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.h b/drivers/gpu/drm/i915/display/intel_tc.h
> index 6719aea5bd58..d44998a3081a 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.h
> +++ b/drivers/gpu/drm/i915/display/intel_tc.h
> @@ -108,6 +108,7 @@ bool intel_tc_port_ref_held(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_needs_reset(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_reset(struct intel_digital_port *dig_port);
> void intel_tc_port_link_cancel_reset_work(struct intel_digital_port *dig_port);
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port);
>
> int intel_tc_port_init(struct intel_digital_port *dig_port, bool is_legacy);
> void intel_tc_port_cleanup(struct intel_digital_port *dig_port);
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change
2026-05-05 3:35 [PATCH v2] drm/i915/tc: Recover AUX channel after external TC port mode change ChunAn Wu
2026-05-05 8:02 ` Jani Nikula
2026-05-05 8:34 ` Imre Deak
@ 2026-05-06 18:55 ` Ville Syrjälä
2 siblings, 0 replies; 4+ messages in thread
From: Ville Syrjälä @ 2026-05-06 18:55 UTC (permalink / raw)
To: ChunAn Wu
Cc: Jani Nikula, Rodrigo Vivi, Joonas Lahtinen, Tvrtko Ursulin,
David Airlie, Simona Vetter, intel-gfx, intel-xe, dri-devel,
linux-kernel
On Tue, May 05, 2026 at 11:35:57AM +0800, ChunAn Wu wrote:
> When Fn+F4 triggers mirror mode, the BIOS/EC reconfigures a TC port
> mode (e.g. DP-Alt to TBT-Alt via UCSI) without generating HPD. The
> driver's cached TC mode becomes stale, so intel_dp_aux_xfer() uses
> the wrong power domain and IO routing, and AUX transactions fail.
>
> This occurs when the USB-C-to-HDMI dongle does not support TBT, so
> the mode switch creates a mismatch. It also occurs with slow monitors
> whose delayed HPD/DDC/EDID recovery causes the Type-C layer to settle
> on a stale tbt-alt state before the dongle finishes re-negotiation.
>
> Add intel_tc_port_aux_recover() to detect hardware/cached TC mode
> divergence and reset the PHY. Wrap it with
> intel_dp_aux_xfer_with_recovery() to retry with corrected settings.
>
> Tested on Panther Lake and Lunar Lake with a BenQ HDMI monitor via
> USB-C-to-HDMI dongle.
This sounds like a completely insane thing for the firmware to do.
It's not supposed to screw with the hardware while the driver is in
control.
Please file a bug in gitlab and also attach full acpidumps there so
that we can check if that's where the insanity lives. This is isn't
some Fujitsu-Siemens laptop is it? Those have historically known to
do stupid stuff like this...
>
> Signed-off-by: ChunAn Wu <an.wu@canonical.com>
> ---
> drivers/gpu/drm/i915/display/intel_dp_aux.c | 41 +++++++++--
> drivers/gpu/drm/i915/display/intel_tc.c | 75 +++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_tc.h | 1 +
> 3 files changed, 113 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> index b20ec3e589fa..d496b2231656 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> @@ -481,6 +481,39 @@ static u32 intel_dp_aux_xfer_flags(const struct drm_dp_aux_msg *msg)
> return 0;
> }
>
> +/**
> + * intel_dp_aux_xfer_with_recovery - AUX transfer with TC port recovery
> + * @intel_dp: the DP port
> + * @send: buffer of bytes to send
> + * @send_bytes: number of bytes to send
> + * @recv: buffer to store received reply
> + * @recv_size: maximum number of bytes to receive
> + * @aux_send_ctl_flags: extra flags for the AUX send control register
> + *
> + * Wrapper around intel_dp_aux_xfer() that attempts to recover from an
> + * external TC port mode change (e.g., dp-alt -> tbt-alt via hotkey BIOS
> + * action) when the initial AUX transfer fails. On failure, recovery is
> + * attempted once via intel_tc_port_aux_recover() before retrying.
> + *
> + * Returns: number of received bytes on success, negative error code on failure.
> + */
> +static int
> +intel_dp_aux_xfer_with_recovery(struct intel_dp *intel_dp,
> + const u8 *send, int send_bytes,
> + u8 *recv, int recv_size,
> + u32 aux_send_ctl_flags)
> +{
> + struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> + int ret;
> +
> + ret = intel_dp_aux_xfer(intel_dp, send, send_bytes, recv, recv_size,
> + aux_send_ctl_flags);
> + if (ret < 0 && intel_tc_port_aux_recover(dig_port))
> + ret = intel_dp_aux_xfer(intel_dp, send, send_bytes, recv,
> + recv_size, aux_send_ctl_flags);
> + return ret;
> +}
> +
> static ssize_t
> intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> {
> @@ -508,8 +541,8 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> if (msg->buffer)
> memcpy(txbuf + HEADER_SIZE, msg->buffer, msg->size);
>
> - ret = intel_dp_aux_xfer(intel_dp, txbuf, txsize,
> - rxbuf, rxsize, flags);
> + ret = intel_dp_aux_xfer_with_recovery(intel_dp, txbuf, txsize,
> + rxbuf, rxsize, flags);
> if (ret > 0) {
> msg->reply = rxbuf[0] >> 4;
>
> @@ -531,8 +564,8 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
> if (drm_WARN_ON(display->drm, rxsize > 20))
> return -E2BIG;
>
> - ret = intel_dp_aux_xfer(intel_dp, txbuf, txsize,
> - rxbuf, rxsize, flags);
> + ret = intel_dp_aux_xfer_with_recovery(intel_dp, txbuf, txsize,
> + rxbuf, rxsize, flags);
> if (ret > 0) {
> msg->reply = rxbuf[0] >> 4;
> /*
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index a21dd4e3fe4c..1b23161e4eea 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -1861,6 +1861,81 @@ void intel_tc_port_link_cancel_reset_work(struct intel_digital_port *dig_port)
> cancel_delayed_work(&tc->link_reset_work);
> }
>
> +/**
> + * intel_tc_port_aux_recover - Recover AUX channel after external TC mode change
> + * @dig_port: digital port
> + *
> + * When firmware causes a TC port mode change (e.g., dp-alt -> disconnect ->
> + * tbt-alt) during a hotkey-triggered display mode switch, AUX transactions
> + * using the stale power domain and IO flags will fail with timeouts or errors.
> + * This happens because:
> + *
> + * 1. The display driver holds the TC link in dp-alt mode (link_refcount > 0)
> + * 2. Firmware (e.g., via HP WMI hotkey BIOS action) reconfigures the TC port
> + * mode externally without notifying the display driver
> + * 3. tc->mode stays as TC_PORT_DP_ALT while HW transitions to a different
> + * mode, invalidating the AUX power domain and IO flags used by
> + * intel_dp_aux_xfer()
> + *
> + * This function detects the discrepancy between tc->mode and actual HW state,
> + * and re-synchronizes them via a TC PHY reset. After recovery, AUX retries
> + * will use the correct power domain and control flags.
> + *
> + * The link_refcount is temporarily cleared to allow intel_tc_port_reset_mode()
> + * to proceed without the PHY-ownership assertion that fires when link_refcount
> + * is non-zero and firmware has already released PHY ownership.
> + *
> + * Must be called outside the TC port lock (tc->lock).
> + *
> + * Returns: %true if recovery was performed and AUX can be retried,
> + * %false if recovery was not needed or not possible.
> + */
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port)
> +{
> + struct intel_tc_port *tc;
> + struct intel_display *display;
> + bool recovered = false;
> +
> + if (!intel_encoder_is_tc(&dig_port->base))
> + return false;
> +
> + tc = to_tc_port(dig_port);
> + display = to_intel_display(dig_port);
> +
> + mutex_lock(&tc->lock);
> +
> + /*
> + * Recovery is only needed when the link is actively held AND the HW
> + * TC mode has diverged from the driver's cached state.
> + */
> + if (!tc->link_refcount || !intel_tc_port_needs_reset(tc))
> + goto out;
> +
> + drm_dbg_kms(display->drm,
> + "Port %s: AUX recover: external TC mode change detected (%s -> HW), reconnecting TC PHY\n",
> + tc->port_name, tc_port_mode_name(tc->mode));
> +
> + /*
> + * Temporarily clear link_refcount so intel_tc_port_reset_mode() can
> + * run the PHY disconnect/connect cycle without the ownership assertion
> + * that fires when link_refcount > 0 and firmware has already released
> + * PHY ownership externally.
> + */
> + tc->link_refcount = 0;
> + intel_tc_port_reset_mode(tc, 1, false);
> + tc->link_refcount = 1;
> +
> + recovered = tc->mode != TC_PORT_DISCONNECTED;
> + if (!recovered)
> + drm_warn(display->drm,
> + "Port %s: AUX recover: failed to restore TC port mode\n",
> + tc->port_name);
> +
> +out:
> + mutex_unlock(&tc->lock);
> + return recovered;
> +}
> +
> static void __intel_tc_port_lock(struct intel_tc_port *tc,
> int required_lanes)
> {
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.h b/drivers/gpu/drm/i915/display/intel_tc.h
> index 6719aea5bd58..d44998a3081a 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.h
> +++ b/drivers/gpu/drm/i915/display/intel_tc.h
> @@ -108,6 +108,7 @@ bool intel_tc_port_ref_held(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_needs_reset(struct intel_digital_port *dig_port);
> bool intel_tc_port_link_reset(struct intel_digital_port *dig_port);
> void intel_tc_port_link_cancel_reset_work(struct intel_digital_port *dig_port);
> +bool intel_tc_port_aux_recover(struct intel_digital_port *dig_port);
>
> int intel_tc_port_init(struct intel_digital_port *dig_port, bool is_legacy);
> void intel_tc_port_cleanup(struct intel_digital_port *dig_port);
> --
> 2.34.1
--
Ville Syrjälä
Intel
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