linux-kernel - Re: [PATCH v2] usb: typec: tcpm: Use configured PD revision for negotiation

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Message-ID: <aCNOOXcAuA_1B-0Z@kuha.fi.intel.com>
Date: Tue, 13 May 2025 16:50:49 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Cosmo Chou <chou.cosmo@...il.com>
Cc: badhri@...gle.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	cosmo.chou@...ntatw.com
Subject: Re: [PATCH v2] usb: typec: tcpm: Use configured PD revision for
 negotiation

On Tue, May 13, 2025 at 04:39:09PM +0300, Heikki Krogerus wrote:
> On Tue, May 13, 2025 at 09:08:34PM +0800, Cosmo Chou wrote:
> > Initialize negotiated_rev and negotiated_rev_prime based on the port's
> > configured PD revision (rev_major) rather than always defaulting to
> > PD_MAX_REV. This ensures ports start PD communication using their
> > appropriate revision level.
> > 
> > This allows proper communication with devices that require specific
> > PD revision levels, especially for the hardware designed for PD 1.0
> > or 2.0 specifications.
> > 
> > Signed-off-by: Cosmo Chou <chou.cosmo@...il.com>
> > ---
> > Change log:
> > 
> > v2:
> >   - Add PD_CAP_REVXX macros and use switch-case for better readability.
> > 
> > ---
> >  drivers/usb/typec/tcpm/tcpm.c | 29 +++++++++++++++++++++++++----
> >  1 file changed, 25 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 8adf6f954633..48e9cfc2b49a 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -313,6 +313,10 @@ struct pd_data {
> >  	unsigned int operating_snk_mw;
> >  };
> >  
> > +#define PD_CAP_REV10	0x1
> > +#define PD_CAP_REV20	0x2
> > +#define PD_CAP_REV30	0x3
> > +
> >  struct pd_revision_info {
> >  	u8 rev_major;
> >  	u8 rev_minor;
> > @@ -4665,6 +4669,25 @@ static void tcpm_set_initial_svdm_version(struct tcpm_port *port)
> >  	}
> >  }
> >  
> > +static void tcpm_set_initial_negotiated_rev(struct tcpm_port *port)
> > +{
> > +	switch (port->pd_rev.rev_major) {
> > +	case PD_CAP_REV10:
> > +		port->negotiated_rev = PD_REV10;
> > +		break;
> > +	case PD_CAP_REV20:
> > +		port->negotiated_rev = PD_REV20;
> > +		break;
> > +	case PD_CAP_REV30:
> > +		port->negotiated_rev = PD_REV30;
> > +		break;
> > +	default:
> > +		port->negotiated_rev = PD_MAX_REV;
> > +		break;
> > +	}
> > +	port->negotiated_rev_prime = port->negotiated_rev;
> > +}
> 
> Do we need this? Couldn't you just add one to rev_major?
> 
>         port->negotiated_rev = port->pd_rev.rev_major + 1;
>         port->negotiated_rev_prime = port->pd_rev.rev_major + 1;
> 
> Or am I missing something?

Sorry, I mean minus one :-)

        port->negotiated_rev = port->pd_rev.rev_major - 1;
        port->negotiated_rev_prime = port->pd_rev.rev_major - 1;

-- 
heikki