linux-kernel - Re: [PATCH v2] tcpm: During PR_SWAP, source caps should be sent only after tSwapSourceStart

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Date:   Tue, 11 Aug 2020 18:43:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tcpm: During PR_SWAP, source caps should be sent only
 after tSwapSourceStart

On Tue, Aug 11, 2020 at 05:14:39PM -0700, Badhri Jagan Sridharan wrote:
> From the spec:
> "6.6.8.1 SwapSourceStartTimer
> The SwapSourceStartTimer Shall be used by the new Source, after a Power
> Role Swap or Fast Role Swap, to ensure that it does not send
> Source_Capabilities Message before the new Sink is ready to receive the
> Source_Capabilities Message. The new Source Shall Not send the
> Source_Capabilities Message earlier than tSwapSourceStart after the
> last bit of the EOP of GoodCRC Message sent in response to the PS_RDY
> Message sent by the new Source indicating that its power supply is
> ready."
> 
> This fixes TD.PD.CP.E3, TD.PD.CP.E4, TD.PD.CP.E5 failures
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

Nit below, otherwise

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

Note that I wasn't copied on this patch and only noticed it accidentally.

Guenter

> ---
> Changes since V1:
> - Comment on the permissible values of tSwapSourceStart
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 2 +-
>  include/linux/usb/pd.h        | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 3ef37202ee37..d38347bd3335 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -3555,7 +3555,7 @@ static void run_state_machine(struct tcpm_port *port)
>  		 */
>  		tcpm_set_pwr_role(port, TYPEC_SOURCE);
>  		tcpm_pd_send_control(port, PD_CTRL_PS_RDY);
> -		tcpm_set_state(port, SRC_STARTUP, 0);
> +		tcpm_set_state(port, SRC_STARTUP, PD_T_SWAP_SRC_START);
>  		break;
>  
>  	case VCONN_SWAP_ACCEPT:
> diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
> index b6c233e79bd4..ed5eed73ccf8 100644
> --- a/include/linux/usb/pd.h
> +++ b/include/linux/usb/pd.h
> @@ -473,6 +473,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
>  #define PD_T_ERROR_RECOVERY	100	/* minimum 25 is insufficient */
>  #define PD_T_SRCSWAPSTDBY      625     /* Maximum of 650ms */
>  #define PD_T_NEWSRC            250     /* Maximum of 275ms */
> +#define PD_T_SWAP_SRC_START	20     /* Minimum of 20ms */

Odd alignment. Same as with the previous two lines which don't use tabs
either.

>  
>  #define PD_T_DRP_TRY		100	/* 75 - 150 ms */
>  #define PD_T_DRP_TRYWAIT	600	/* 400 - 800 ms */