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

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Message-ID: <cd4f50fd-e418-45e0-81d8-0d34a5431a28@google.com>
Date: Mon, 12 May 2025 15:00:25 -0700
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: Cosmo Chou <chou.cosmo@...il.com>, badhri@...gle.com,
 heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
 cosmo.chou@...ntatw.com, "kyletso@...gle.com" <Kyletso@...gle.com>,
 "rdbabiera@...gle.com" <rdbabiera@...gle.com>
Subject: Re: [PATCH] usb: typec: tcpm: Use configured PD revision for
 negotiation

Hi Cosmo,

Thanks for the patch!

On 5/8/25 10:47 AM, 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
I didn't know PD1.0 is still used.
> or 2.0 specifications.
>
> Signed-off-by: Cosmo Chou <chou.cosmo@...il.com>
> ---
>   drivers/usb/typec/tcpm/tcpm.c | 18 ++++++++++++++----
>   1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index a99db4e025cd..5a58c21c4d14 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4782,8 +4782,13 @@ static void run_state_machine(struct tcpm_port *port)
>   		typec_set_pwr_opmode(port->typec_port, opmode);
>   		port->pwr_opmode = TYPEC_PWR_MODE_USB;
>   		port->caps_count = 0;
> -		port->negotiated_rev = PD_MAX_REV;
> -		port->negotiated_rev_prime = PD_MAX_REV;
> +		if (port->pd_rev.rev_major > 0 && port->pd_rev.rev_major <= PD_MAX_REV + 1) {

For better readability, I'd prefer you use macros for the numerical 
values and implement this logic as a switch case. This would make the 
value difference between PD specification revision in PD Message header 
vs PD max revision AMS transparent to the reader.

Thanks,

Amit

> +			port->negotiated_rev = port->pd_rev.rev_major - 1;
> +			port->negotiated_rev_prime = port->pd_rev.rev_major - 1;
> +		} else {
> +			port->negotiated_rev = PD_MAX_REV;
> +			port->negotiated_rev_prime = PD_MAX_REV;
> +		}
>   		port->message_id = 0;
>   		port->message_id_prime = 0;
>   		port->rx_msgid = -1;
> @@ -5048,8 +5053,13 @@ static void run_state_machine(struct tcpm_port *port)
>   					      port->cc2 : port->cc1);
>   		typec_set_pwr_opmode(port->typec_port, opmode);
>   		port->pwr_opmode = TYPEC_PWR_MODE_USB;
> -		port->negotiated_rev = PD_MAX_REV;
> -		port->negotiated_rev_prime = PD_MAX_REV;
> +		if (port->pd_rev.rev_major > 0 && port->pd_rev.rev_major <= PD_MAX_REV + 1) {
> +			port->negotiated_rev = port->pd_rev.rev_major - 1;
> +			port->negotiated_rev_prime = port->pd_rev.rev_major - 1;
> +		} else {
> +			port->negotiated_rev = PD_MAX_REV;
> +			port->negotiated_rev_prime = PD_MAX_REV;
> +		}
>   		port->message_id = 0;
>   		port->message_id_prime = 0;
>   		port->rx_msgid = -1;