On Thu, Jan 21, 2021 at 4:41 PM Heikki Krogerus
<heikki.krogerus@xxxxxxxxxxxxxxx> wrote:
>
> Hi Kyle,
>
> On Sat, Jan 16, 2021 at 12:33:11AM +0800, Kyle Tso wrote:
> > If the port partner is PD2, the PDOs of the local port should follow the
> > format defined in PD2 Spec. Dynamically modify the pre-defined PD3 PDOs
> > and transform them into PD2 format before sending them to the PD2 port
> > partner.
>
> I guess it's not possible for the system to supply separate static
> PDOs for each PD revision?
>
We can do that for sure. But a problem is that if there are more PD
revisions in the future, we will need to add more PDO arrays.
For backward compatibility, the new revision usually uses the
previously-reserved bits for the new features.
>From my perspective, the better way to achieve the backward
compatibility is to just clear the bits if those are reserved in the
previous revision.
I can submit another patch which adds another PDO array for PD2 if you
think it is more appropriate.
> > Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
> > ---
> > drivers/usb/typec/tcpm/tcpm.c | 62 +++++++++++++++++++++++++++++------
> > include/linux/usb/pd.h | 1 +
> > 2 files changed, 53 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 22a85b396f69..1220ab1ed47d 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -911,13 +911,47 @@ static int tcpm_set_pwr_role(struct tcpm_port *port, enum typec_role role)
> > return 0;
> > }
> >
> > +/*
> > + * Transform the PDO to be compliant to PD rev2.0.
> > + * Return 0 if the PDO type is not defined in PD rev2.0.
> > + * Otherwise, return the converted PDO.
> > + */
> > +static u32 tcpm_forge_legacy_pdo(struct tcpm_port *port, u32 pdo, enum typec_role role)
> > +{
> > + switch (pdo_type(pdo)) {
> > + case PDO_TYPE_FIXED:
> > + if (role == TYPEC_SINK)
> > + return pdo & ~PDO_FIXED_FRS_CURR_MASK;
> > + else
> > + return pdo & ~PDO_FIXED_UNCHUNK_EXT;
> > + case PDO_TYPE_VAR:
> > + case PDO_TYPE_BATT:
> > + return pdo;
> > + case PDO_TYPE_APDO:
> > + default:
> > + return 0;
> > + }
> > +}
> > +
> > static int tcpm_pd_send_source_caps(struct tcpm_port *port)
> > {
> > struct pd_message msg;
> > - int i;
> > + u32 pdo;
> > + unsigned int i, nr_pdo = 0;
>
> Side note. I think this driver uses the "reverse christmas tree"
> style with the variables.
I will change the order (if there is a next version)
thanks,
Kyle
