linux-kernel - Re: [PATCH 09/11] staging: typec: tcpm: typec: tcpm: Wait for CC debounce before PD excg

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Date:   Sun, 27 Aug 2017 10:26:52 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/11] staging: typec: tcpm: typec: tcpm: Wait for CC
 debounce before PD excg

On Sat, Aug 26, 2017 at 11:51:27PM -0700, Badhri Jagan Sridharan wrote:
> Once, Rp or Rd is switched, wait for PD_T_CC_DEBOUNCE. If not the
> PS_RDY message transmitted might result in failure.
> Also, Only wait for PD_T_SRCSWAPSTDBY while in
> PR_SWAP_SRC_SNK_TRANSITION_OFF. PD_T_PS_SOURCE_OFF is the overall
> time after which the initial sink would issue hard reset.
> 
> Signed-off-by: Badhri Jagan Sridharan <Badhri@...gle.com>

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

> ---
>  drivers/staging/typec/pd.h   |  2 ++
>  drivers/staging/typec/tcpm.c | 25 ++++++++++++++++++++++---
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/typec/pd.h b/drivers/staging/typec/pd.h
> index 510ef7279900..30b32ad72acd 100644
> --- a/drivers/staging/typec/pd.h
> +++ b/drivers/staging/typec/pd.h
> @@ -278,6 +278,8 @@ static inline unsigned int rdo_max_power(u32 rdo)
>  #define PD_T_VCONN_SOURCE_ON	100
>  #define PD_T_SINK_REQUEST	100	/* 100 ms minimum */
>  #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_DRP_TRY		100	/* 75 - 150 ms */
>  #define PD_T_DRP_TRYWAIT	600	/* 400 - 800 ms */
> diff --git a/drivers/staging/typec/tcpm.c b/drivers/staging/typec/tcpm.c
> index 1f6827f32b29..a7da609006f5 100644
> --- a/drivers/staging/typec/tcpm.c
> +++ b/drivers/staging/typec/tcpm.c
> @@ -90,9 +90,11 @@
>  	S(PR_SWAP_START),			\
>  	S(PR_SWAP_SRC_SNK_TRANSITION_OFF),	\
>  	S(PR_SWAP_SRC_SNK_SOURCE_OFF),		\
> +	S(PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED), \
>  	S(PR_SWAP_SRC_SNK_SINK_ON),		\
>  	S(PR_SWAP_SNK_SRC_SINK_OFF),		\
>  	S(PR_SWAP_SNK_SRC_SOURCE_ON),		\
> +	S(PR_SWAP_SNK_SRC_SOURCE_ON_VBUS_RAMPED_UP),    \
>  						\
>  	S(VCONN_SWAP_ACCEPT),			\
>  	S(VCONN_SWAP_SEND),			\
> @@ -1395,7 +1397,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>  					       SNK_TRANSITION_SINK_VBUS, 0);
>  			}
>  			break;
> -		case PR_SWAP_SRC_SNK_SOURCE_OFF:
> +		case PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED:
>  			tcpm_set_state(port, PR_SWAP_SRC_SNK_SINK_ON, 0);
>  			break;
>  		case PR_SWAP_SNK_SRC_SINK_OFF:
> @@ -2679,11 +2681,17 @@ static void run_state_machine(struct tcpm_port *port)
>  	case PR_SWAP_SRC_SNK_TRANSITION_OFF:
>  		tcpm_set_vbus(port, false);
>  		port->explicit_contract = false;
> +		/* allow time for Vbus discharge, must be < tSrcSwapStdby */
>  		tcpm_set_state(port, PR_SWAP_SRC_SNK_SOURCE_OFF,
> -			       PD_T_PS_SOURCE_OFF);
> +			       PD_T_SRCSWAPSTDBY);
>  		break;
>  	case PR_SWAP_SRC_SNK_SOURCE_OFF:
>  		tcpm_set_cc(port, TYPEC_CC_RD);
> +		/* allow CC debounce */
> +		tcpm_set_state(port, PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED,
> +			       PD_T_CC_DEBOUNCE);
> +		break;
> +	case PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED:
>  		/*
>  		 * USB-PD standard, 6.2.1.4, Port Power Role:
>  		 * "During the Power Role Swap Sequence, for the initial Source
> @@ -2709,6 +2717,15 @@ static void run_state_machine(struct tcpm_port *port)
>  	case PR_SWAP_SNK_SRC_SOURCE_ON:
>  		tcpm_set_cc(port, tcpm_rp_cc(port));
>  		tcpm_set_vbus(port, true);
> +		/*
> +		 * allow time VBUS ramp-up, must be < tNewSrc
> +		 * Also, this window overlaps with CC debounce as well.
> +		 * So, Wait for the max of two which is PD_T_NEWSRC
> +		 */
> +		tcpm_set_state(port, PR_SWAP_SNK_SRC_SOURCE_ON_VBUS_RAMPED_UP,
> +			       PD_T_NEWSRC);
> +		break;
> +	case PR_SWAP_SNK_SRC_SOURCE_ON_VBUS_RAMPED_UP:
>  		/*
>  		 * USB PD standard, 6.2.1.4:
>  		 * "Subsequent Messages initiated by the Policy Engine,
> @@ -2979,8 +2996,10 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
>  	case PR_SWAP_SNK_SRC_SINK_OFF:
>  	case PR_SWAP_SRC_SNK_TRANSITION_OFF:
>  	case PR_SWAP_SRC_SNK_SOURCE_OFF:
> +	case PR_SWAP_SRC_SNK_SOURCE_OFF_CC_DEBOUNCED:
> +	case PR_SWAP_SNK_SRC_SOURCE_ON:
>  		/*
> -		 * CC state change is expected here; we just turned off power.
> +		 * CC state change is expected in PR_SWAP
>  		 * Ignore it.
>  		 */
>  		break;
> -- 
> 2.14.1.342.g6490525c54-goog
>