[PATCH v2 0/2] USB Type-C mode selection

[PATCH v2 0/2] USB Type-C mode selection

[Andrei Kuchynski]

This patch series introduces priority-based alternate mode selection
support for cros_ec_typec. 
The base patch series and UCSI support was submitted here:
https://lore.kernel.org/all/20260119131824.2529334-1-akuchynski@chromium.org/

When AP-driven alternate mode selection is active, the driver enforces the
mode_selection bit for each registered Alternate Mode. This blocks
individual altmode drivers from self-activating. Once registration
completes, the driver evaluates USB4 capability. If USB4 is unsupported,
it falls back to priority-based negotiation via typec_mode_selection_start.

Additionally, we swap the registration sequence of the port's alternate
modes. Registering DisplayPort after Thunderbolt correctly ensures DP is
prioritized.

Changes in v2:
- Added this cover letter.
- Rebased on top of the latest platform-chrome tree.
- Tested on Redrix with Linux Fedora 7.3.0-rc5+.
v1 Link:
https://lore.kernel.org/all/20260129131928.794768-1-akuchynski@chromium.org/

Andrei Kuchynski (2):
  platform/chrome: cros_ec_typec: Enforce priority-based mode selection
  platform/chrome: cros_ec_typec: Reorder altmode registration

 drivers/platform/chrome/cros_ec_typec.c      | 61 ++++++++++++++++----
 drivers/platform/chrome/cros_typec_altmode.c |  8 ++-
 2 files changed, 55 insertions(+), 14 deletions(-)

-- 
2.56.0.360.g66cac248cb-goog

[PATCH v2 1/2] platform/chrome: cros_ec_typec: Enforce priority-based mode selection

[Andrei Kuchynski]

The driver sets mode_selection bit for each Alternate mode, thereby
preventing individual altmode drivers from activating their respective
modes.
Once the registration of all Alternate Modes is complete, the driver
verifies if USB4 mode is supported by both the port and the partner and
activates USB4 mode. In cases where USB4 is not supported, the driver
invokes typec_mode_selection_start to initiate the mode selection process
based on mode priorities.
The driver communicates the current Type-C mode to the mode selection
process via typec_altmode_state_update.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/platform/chrome/cros_ec_typec.c      | 39 +++++++++++++++++++-
 drivers/platform/chrome/cros_typec_altmode.c |  8 +++-
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index 50a68819ceb7b..718d06fa24132 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -27,6 +27,11 @@
 						BIT(DP_PIN_ASSIGN_D) | \
 						BIT(DP_PIN_ASSIGN_E)))
 
+/* Delay between mode entry/exit attempts, ms */
+static const unsigned int mode_selection_delay = 1000;
+/* Timeout for a mode entry attempt, ms */
+static const unsigned int mode_selection_timeout = 4000;
+
 static void cros_typec_role_switch_quirk(struct fwnode_handle *fwnode)
 {
 #ifdef CONFIG_ACPI
@@ -325,6 +330,7 @@ static void cros_typec_remove_partner(struct cros_typec_data *typec,
 	if (!port->partner)
 		return;
 
+	typec_mode_selection_delete(port->partner);
 	cros_typec_unregister_altmodes(typec, port_num, true);
 
 	typec_partner_set_usb_power_delivery(port->partner, NULL);
@@ -421,7 +427,6 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
 		memset(&desc, 0, sizeof(desc));
 		desc.svid = USB_TYPEC_TBT_SID;
 		desc.mode = TBT_MODE;
-		desc.inactive = true;
 		amode = cros_typec_register_thunderbolt(port, &desc);
 		if (IS_ERR(amode))
 			return PTR_ERR(amode);
@@ -742,6 +747,7 @@ static int cros_typec_configure_mux(struct cros_typec_data *typec, int port_num,
 	enum typec_orientation orientation;
 	struct cros_typec_altmode_node *node;
 	int ret;
+	u16 active_svid = 0;
 
 	ret = cros_ec_cmd(typec->ec, 0, EC_CMD_USB_PD_MUX_INFO,
 			  &req, sizeof(req), &resp, sizeof(resp));
@@ -782,8 +788,10 @@ static int cros_typec_configure_mux(struct cros_typec_data *typec, int port_num,
 		ret = cros_typec_enable_usb4(typec, port_num, pd_ctrl);
 	} else if (port->mux_flags & USB_PD_MUX_TBT_COMPAT_ENABLED) {
 		ret = cros_typec_enable_tbt(typec, port_num, pd_ctrl);
+		active_svid = USB_TYPEC_TBT_SID;
 	} else if (port->mux_flags & USB_PD_MUX_DP_ENABLED) {
 		ret = cros_typec_enable_dp(typec, port_num, pd_ctrl);
+		active_svid = USB_TYPEC_DP_SID;
 	} else if (port->mux_flags & USB_PD_MUX_SAFE_MODE) {
 		ret = cros_typec_usb_safe_state(port);
 	} else if (port->mux_flags & USB_PD_MUX_USB_ENABLED) {
@@ -799,6 +807,9 @@ static int cros_typec_configure_mux(struct cros_typec_data *typec, int port_num,
 			port->mux_flags);
 	}
 
+	if (port->partner)
+		typec_altmode_state_update(port->partner, active_svid, ret);
+
 	/* Iterate all partner alt-modes and set the active alternate mode. */
 	list_for_each_entry(node, &port->partner_mode_list, list) {
 		typec_altmode_update_active(
@@ -900,6 +911,7 @@ static int cros_typec_register_altmodes(struct cros_typec_data *typec, int port_
 			desc.svid = sop_disc->svids[i].svid;
 			desc.mode = j + 1;
 			desc.vdo = sop_disc->svids[i].mode_vdo[j];
+			desc.mode_selection = typec->ap_driven_altmode;
 
 			if (is_partner)
 				amode = typec_partner_register_altmode(port->partner, &desc);
@@ -940,6 +952,31 @@ static int cros_typec_register_altmodes(struct cros_typec_data *typec, int port_
 		goto err_cleanup;
 	}
 
+	/* Once all partner alt-modes are added, we should also trigger
+	 * mode selection.
+	 */
+	if (is_partner && typec->ap_driven_altmode) {
+		bool usb4_mode = (port->caps.usb_capability & USB_CAPABILITY_USB4) &&
+			(PD_VDO_UFP_DEVCAP(port->p_identity.vdo[0]) & DEV_USB4_CAPABLE);
+
+		if (usb4_mode) {
+			ret = cros_typec_enter_usb_mode(port->port, USB_MODE_USB4);
+			if (ret < 0) {
+				usb4_mode = false;
+				dev_err(typec->dev,
+					"Unable to activate USB4 mode, port: %d\n", port_num);
+			}
+		}
+		if (!usb4_mode) {
+			ret = typec_mode_selection_start(port->partner,
+							 mode_selection_delay,
+							 mode_selection_timeout);
+			if (ret < 0)
+				dev_err(typec->dev,
+					"Unable to run mode selection, port: %d\n", port_num);
+		}
+	}
+
 	return 0;
 
 err_cleanup:
diff --git a/drivers/platform/chrome/cros_typec_altmode.c b/drivers/platform/chrome/cros_typec_altmode.c
index 66c546bf89b53..116329dd113f8 100644
--- a/drivers/platform/chrome/cros_typec_altmode.c
+++ b/drivers/platform/chrome/cros_typec_altmode.c
@@ -41,12 +41,16 @@ static void cros_typec_altmode_work(struct work_struct *work)
 {
 	struct cros_typec_altmode_data *data =
 		container_of(work, struct cros_typec_altmode_data, work);
+	int ret;
 
 	mutex_lock(&data->lock);
 
-	if (typec_altmode_vdm(data->alt, data->header, data->vdo_data,
-			      data->vdo_size))
+	ret = typec_altmode_vdm(data->alt, data->header, data->vdo_data,
+				data->vdo_size);
+	if (ret) {
 		dev_err(&data->alt->dev, "VDM 0x%x failed\n", data->header);
+		typec_altmode_state_update(data->port->partner, data->sid, ret);
+	}
 
 	data->header = 0;
 	data->vdo_data = NULL;
-- 
2.56.0.360.g66cac248cb-goog

[PATCH v2 2/2] platform/chrome: cros_ec_typec: Reorder altmode registration

[Andrei Kuchynski]

By default, alternate mode priorities are set in registration order, with
the last mode registered taking precedence. Changing the registration order
of alternate modes prioritizes DisplayPort over Thunderbolt.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/platform/chrome/cros_ec_typec.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index 718d06fa24132..b1bcf2ffb4176 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -406,17 +406,6 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
 	struct typec_altmode_desc desc;
 	struct typec_altmode *amode;
 
-	/* All PD capable CrOS devices are assumed to support DP altmode. */
-	memset(&desc, 0, sizeof(desc));
-	desc.svid = USB_TYPEC_DP_SID;
-	desc.mode = USB_TYPEC_DP_MODE;
-	desc.vdo = DP_PORT_VDO;
-	amode = cros_typec_register_displayport(port, &desc,
-						typec->ap_driven_altmode);
-	if (IS_ERR(amode))
-		return PTR_ERR(amode);
-	port->port_altmode[CROS_EC_ALTMODE_DP] = amode;
-
 	/*
 	 * Register TBT compatibility alt mode. The EC will not enter the mode
 	 * if it doesn't support it and it will not enter automatically by
@@ -433,6 +422,17 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
 		port->port_altmode[CROS_EC_ALTMODE_TBT] = amode;
 	}
 
+	/* All PD capable CrOS devices are assumed to support DP altmode. */
+	memset(&desc, 0, sizeof(desc));
+	desc.svid = USB_TYPEC_DP_SID;
+	desc.mode = USB_TYPEC_DP_MODE;
+	desc.vdo = DP_PORT_VDO;
+	amode = cros_typec_register_displayport(port, &desc,
+						typec->ap_driven_altmode);
+	if (IS_ERR(amode))
+		return PTR_ERR(amode);
+	port->port_altmode[CROS_EC_ALTMODE_DP] = amode;
+
 	port->state.alt = NULL;
 	port->state.mode = TYPEC_STATE_USB;
 	port->state.data = NULL;
-- 
2.56.0.360.g66cac248cb-goog

Re: [PATCH v2 2/2] platform/chrome: cros_ec_typec: Reorder altmode registration

[Tzung-Bi Shih]

On Thu, Oct 08, 2026 at 01:40:56PM +0000, Andrei Kuchynski wrote:
> @@ -406,17 +406,6 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
>  	struct typec_altmode_desc desc;
>  	struct typec_altmode *amode;
>  
> -	/* All PD capable CrOS devices are assumed to support DP altmode. */
> -	memset(&desc, 0, sizeof(desc));
> -	desc.svid = USB_TYPEC_DP_SID;
> -	desc.mode = USB_TYPEC_DP_MODE;
> -	desc.vdo = DP_PORT_VDO;
> -	amode = cros_typec_register_displayport(port, &desc,
> -						typec->ap_driven_altmode);
> -	if (IS_ERR(amode))
> -		return PTR_ERR(amode);
> -	port->port_altmode[CROS_EC_ALTMODE_DP] = amode;
> -
>  	/*
>  	 * Register TBT compatibility alt mode. The EC will not enter the mode
>  	 * if it doesn't support it and it will not enter automatically by
> @@ -433,6 +422,17 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
>  		port->port_altmode[CROS_EC_ALTMODE_TBT] = amode;
>  	}
>  
> +	/* All PD capable CrOS devices are assumed to support DP altmode. */
> +	memset(&desc, 0, sizeof(desc));
> +	desc.svid = USB_TYPEC_DP_SID;
> +	desc.mode = USB_TYPEC_DP_MODE;
> +	desc.vdo = DP_PORT_VDO;
> +	amode = cros_typec_register_displayport(port, &desc,
> +						typec->ap_driven_altmode);
> +	if (IS_ERR(amode))
> +		return PTR_ERR(amode);
> +	port->port_altmode[CROS_EC_ALTMODE_DP] = amode;
> +

It deserves a code comment to note that the registration order dictates
the priorities.

Re: [PATCH v2 1/2] platform/chrome: cros_ec_typec: Enforce priority-based mode selection

[Tzung-Bi Shih]

On Thu, Oct 08, 2026 at 01:40:55PM +0000, Andrei Kuchynski wrote:
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
...
> +/* Delay between mode entry/exit attempts, ms */
> +static const unsigned int mode_selection_delay = 1000;
> +/* Timeout for a mode entry attempt, ms */
> +static const unsigned int mode_selection_timeout = 4000;

Couldn't they be macros?

> @@ -421,7 +427,6 @@ static int cros_typec_register_port_altmodes(struct cros_typec_data *typec,
>  		memset(&desc, 0, sizeof(desc));
>  		desc.svid = USB_TYPEC_TBT_SID;
>  		desc.mode = TBT_MODE;
> -		desc.inactive = true;

Why this is removed?  Per 1aede0698167 ("platform/chrome: cros_ec_typec:
Disable tbt on port"), it disables entering TBT mode automatically.

> @@ -940,6 +952,31 @@ static int cros_typec_register_altmodes(struct cros_typec_data *typec, int port_
>  		goto err_cleanup;
>  	}
>  
> +	/* Once all partner alt-modes are added, we should also trigger
> +	 * mode selection.
> +	 */

For multiple line comments:

    /*
     * Once ...

> +	if (is_partner && typec->ap_driven_altmode) {
> +		bool usb4_mode = (port->caps.usb_capability & USB_CAPABILITY_USB4) &&
> +			(PD_VDO_UFP_DEVCAP(port->p_identity.vdo[0]) & DEV_USB4_CAPABLE);
> +
> +		if (usb4_mode) {
> +			ret = cros_typec_enter_usb_mode(port->port, USB_MODE_USB4);
> +			if (ret < 0) {
> +				usb4_mode = false;
> +				dev_err(typec->dev,
> +					"Unable to activate USB4 mode, port: %d\n", port_num);
> +			}
> +		}
> +		if (!usb4_mode) {
> +			ret = typec_mode_selection_start(port->partner,
> +							 mode_selection_delay,
> +							 mode_selection_timeout);
> +			if (ret < 0)
> +				dev_err(typec->dev,
> +					"Unable to run mode selection, port: %d\n", port_num);

Wouldn't it need to go to err_cleanup and return the ret?  Or, if they
aren't considered as errors, dev_warn().

> diff --git a/drivers/platform/chrome/cros_typec_altmode.c b/drivers/platform/chrome/cros_typec_altmode.c
> index 66c546bf89b53..116329dd113f8 100644
> --- a/drivers/platform/chrome/cros_typec_altmode.c
> +++ b/drivers/platform/chrome/cros_typec_altmode.c
> @@ -41,12 +41,16 @@ static void cros_typec_altmode_work(struct work_struct *work)
>  {
>  	struct cros_typec_altmode_data *data =
>  		container_of(work, struct cros_typec_altmode_data, work);
> +	int ret;
>  
>  	mutex_lock(&data->lock);
>  
> -	if (typec_altmode_vdm(data->alt, data->header, data->vdo_data,
> -			      data->vdo_size))
> +	ret = typec_altmode_vdm(data->alt, data->header, data->vdo_data,
> +				data->vdo_size);
> +	if (ret) {
>  		dev_err(&data->alt->dev, "VDM 0x%x failed\n", data->header);
> +		typec_altmode_state_update(data->port->partner, data->sid, ret);
> +	}

Wouldn't it need to update the state even if !ret?