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Date: Mon, 1 Feb 2021 14:40:24 +0200
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Benson Leung <bleung@...omium.org>
Cc: enric.balletbo@...labora.com, pmalani@...omium.org,
gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org, groeck@...omium.org,
bleung@...gle.com
Subject: Re: [PATCH 2/6] usb: typec: Provide PD Specification Revision for
cable and partner
On Thu, Jan 28, 2021 at 10:14:02PM -0800, Benson Leung wrote:
> The USB Power Delivery specification Section 6.2.1.1.5 outlines
> revision backward compatibility requirements starting from Revision 3.0.
>
> The Port, the Cable Plug, and the Port Partner may support either
> revision 2 or revision 3 independently, and communication between ports,
> partners, and cables of different revisions are allowed under rules
> that the parties agree to communicate between each other using the
> lowest common operating revision.
>
> This may mean that Port-to-Partner operating revision comms may be
> different than Port-to-CablePlug operating revision comms. For example,
> it is possible for a R3.0 port to communicate with a R3.0 partner
> using R3.0 messages, while the R3.0 port (in the same session) must
> communicate with the R2.0 cable using R2.0 messages only.
>
> Introduce individual revision number properties for cable
> and port partner so that the port can track them independently.
>
> Signed-off-by: Benson Leung <bleung@...omium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
> Documentation/ABI/testing/sysfs-class-typec | 13 +++++++++
> drivers/usb/typec/class.c | 30 ++++++++++++++++++---
> include/linux/usb/typec.h | 10 +++++++
> 3 files changed, 49 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> index b61480535fdc..40122d915ae1 100644
> --- a/Documentation/ABI/testing/sysfs-class-typec
> +++ b/Documentation/ABI/testing/sysfs-class-typec
> @@ -112,6 +112,19 @@ Description:
> - "3.0": USB Power Delivery Release 3.0
> - "3.1": USB Power Delivery Release 3.1
>
> +What: /sys/class/typec/<port>-{partner|cable}/usb_power_delivery_revision
> +Date: January 2021
> +Contact: Benson Leung <bleung@...omium.org>
> +Description:
> + Revision number of the supported USB Power Delivery
> + specification of the port partner or cable, or 0.0 when USB
> + Power Delivery is not supported.
> +
> + Example values:
> + - "2.0": USB Power Delivery Release 2.0
> + - "3.0": USB Power Delivery Release 3.0
> + - "3.1": USB Power Delivery Release 3.1
> +
> What: /sys/class/typec/<port>/usb_typec_revision
> Date: April 2017
> Contact: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index 4f60ee7ba76a..b5241f4756c2 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -27,6 +27,7 @@ struct typec_cable {
> enum typec_plug_type type;
> struct usb_pd_identity *identity;
> unsigned int active:1;
> + u16 pd_revision; /* 0300H = "3.0" */
> };
>
> struct typec_partner {
> @@ -36,6 +37,7 @@ struct typec_partner {
> enum typec_accessory accessory;
> struct ida mode_ids;
> int num_altmodes;
> + u16 pd_revision; /* 0300H = "3.0" */
> };
>
> struct typec_port {
> @@ -264,6 +266,11 @@ type_show(struct device *dev, struct device_attribute *attr, char *buf)
> }
> static DEVICE_ATTR_RO(type);
>
> +static ssize_t usb_power_delivery_revision_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf);
> +static DEVICE_ATTR_RO(usb_power_delivery_revision);
> +
> /* ------------------------------------------------------------------------- */
> /* Alternate Modes */
>
> @@ -680,6 +687,7 @@ static struct attribute *typec_partner_attrs[] = {
> &dev_attr_supports_usb_power_delivery.attr,
> &dev_attr_number_of_alternate_modes.attr,
> &dev_attr_type.attr,
> + &dev_attr_usb_power_delivery_revision.attr,
> NULL
> };
>
> @@ -815,6 +823,7 @@ struct typec_partner *typec_register_partner(struct typec_port *port,
> partner->usb_pd = desc->usb_pd;
> partner->accessory = desc->accessory;
> partner->num_altmodes = -1;
> + partner->pd_revision = desc->pd_revision;
>
> if (desc->identity) {
> /*
> @@ -1028,6 +1037,7 @@ static DEVICE_ATTR_RO(plug_type);
> static struct attribute *typec_cable_attrs[] = {
> &dev_attr_type.attr,
> &dev_attr_plug_type.attr,
> + &dev_attr_usb_power_delivery_revision.attr,
> NULL
> };
> ATTRIBUTE_GROUPS(typec_cable);
> @@ -1130,6 +1140,7 @@ struct typec_cable *typec_register_cable(struct typec_port *port,
>
> cable->type = desc->type;
> cable->active = desc->active;
> + cable->pd_revision = desc->pd_revision;
>
> if (desc->identity) {
> /*
> @@ -1499,12 +1510,23 @@ static ssize_t usb_power_delivery_revision_show(struct device *dev,
> struct device_attribute *attr,
> char *buf)
> {
> - struct typec_port *p = to_typec_port(dev);
> - u16 rev = p->cap->pd_revision;
> + u16 rev = 0;
>
> - return sprintf(buf, "%d.%d\n", (rev >> 8) & 0xff, (rev >> 4) & 0xf);
> + if (is_typec_partner(dev)) {
> + struct typec_partner *partner = to_typec_partner(dev);
> +
> + rev = partner->pd_revision;
> + } else if (is_typec_cable(dev)) {
> + struct typec_cable *cable = to_typec_cable(dev);
> +
> + rev = cable->pd_revision;
> + } else if (is_typec_port(dev)) {
> + struct typec_port *p = to_typec_port(dev);
> +
> + rev = p->cap->pd_revision;
> + }
> + return sysfs_emit(buf, "%d.%d\n", (rev >> 8) & 0xff, (rev >> 4) & 0xf);
> }
> -static DEVICE_ATTR_RO(usb_power_delivery_revision);
>
> static ssize_t orientation_show(struct device *dev,
> struct device_attribute *attr,
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index 54475323f83b..42c6b7c07a99 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -164,6 +164,7 @@ struct typec_plug_desc {
> * @type: The plug type from USB PD Cable VDO
> * @active: Is the cable active or passive
> * @identity: Result of Discover Identity command
> + * @pd_revision: USB Power Delivery Specification revision if supported
> *
> * Represents USB Type-C Cable attached to USB Type-C port.
> */
> @@ -171,6 +172,8 @@ struct typec_cable_desc {
> enum typec_plug_type type;
> unsigned int active:1;
> struct usb_pd_identity *identity;
> + u16 pd_revision; /* 0300H = "3.0" */
> +
> };
>
> /*
> @@ -178,15 +181,22 @@ struct typec_cable_desc {
> * @usb_pd: USB Power Delivery support
> * @accessory: Audio, Debug or none.
> * @identity: Discover Identity command data
> + * @pd_revision: USB Power Delivery Specification Revision if supported
> *
> * Details about a partner that is attached to USB Type-C port. If @identity
> * member exists when partner is registered, a directory named "identity" is
> * created to sysfs for the partner device.
> + *
> + * @pd_revision is based on the setting of the "Specification Revision" field
> + * in the message header on the initial "Source Capabilities" message received
> + * from the partner, or a "Request" message received from the partner, depending
> + * on whether our port is a Sink or a Source.
> */
> struct typec_partner_desc {
> unsigned int usb_pd:1;
> enum typec_accessory accessory;
> struct usb_pd_identity *identity;
> + u16 pd_revision; /* 0300H = "3.0" */
> };
>
> /**
> --
> 2.30.0.365.g02bc693789-goog
thanks,
--
heikki
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