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commitc97cd0b4b5upstream. When sending Discover Identity messages to a Port Partner that uses Power Delivery v2 and SVDM v1, we currently send PD v2 messages with SVDM v2.0, expecting the port partner to respond with its highest supported SVDM version as stated in Section 6.4.4.2.3 in the Power Delivery v3 specification. However, sending SVDM v2 to some Power Delivery v2 port partners results in a NAK whereas sending SVDM v1 does not. NAK messages can be handled by the initiator (PD v3 section 6.4.4.2.5.1), and one solution could be to resend Discover Identity on a lower SVDM version if possible. But, Section 6.4.4.3 of PD v2 states that "A NAK response Should be taken as an indication not to retry that particular Command." Instead, we can set the SVDM version to the maximum one supported by the negotiated PD revision. When operating in PD v2, this obeys Section 6.4.4.2.3, which states the SVDM field "Shall be set to zero to indicate Version 1.0." In PD v3, the SVDM field "Shall be set to 01b to indicate Version 2.0." Fixes:c34e85fa69("usb: typec: tcpm: Send DISCOVER_IDENTITY from dedicated work") Cc: stable@vger.kernel.org Signed-off-by: RD Babiera <rdbabiera@google.com> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Link: https://lore.kernel.org/r/20230731165926.1815338-1-rdbabiera@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.