linux-kernel - Re: [PATCH v2 3/3] usb: typec: tcpm: Add support for sink-bc12-completion-time-ms DT property

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Message-ID: <f244542a-7160-4f05-acaa-0e2574ee289d@google.com>
Date: Thu, 14 Nov 2024 11:59:41 -0800
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 gregkh@...uxfoundation.org, heikki.krogerus@...ux.intel.com
Cc: dmitry.baryshkov@...aro.org, kyletso@...gle.com, rdbabiera@...gle.com,
 badhri@...gle.com, linux@...ck-us.net, xu.yang_2@....com,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 3/3] usb: typec: tcpm: Add support for
 sink-bc12-completion-time-ms DT property

Hi Heikki,

On 11/2/24 8:43 PM, Amit Sunil Dhamne wrote:
> Add support for parsing DT time property "sink-bc12-completion-time-ms".
> This timer is used to relax the PD state machine during Sink attach to
> allow completion of Battery Charging (BC1.2) charger type detection in
> TCPC before PD negotiations. BC1.2 detection is a hardware mechanism to
> detect charger port type that is run by some controllers (such as
> "maxim,max33359") in parallel to Type-C connection state machines.
> This is to ensure that BC1.2 completes before PD is enabled as running
> BC1.2 in parallel with PD negotiation results in delays violating timer
> constraints in PD spec.
>
> This is an optional timer and will not add any delay unless explicitly
> set.
>
> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
> Reviewed-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
>   drivers/usb/typec/tcpm/tcpm.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index b3d5d1d48937..8b325b93b5a9 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -319,6 +319,7 @@ struct pd_timings {
>   	u32 sink_wait_cap_time;
>   	u32 ps_src_off_time;
>   	u32 cc_debounce_time;
> +	u32 snk_bc12_cmpletion_time;
>   };
>   
>   struct tcpm_port {
> @@ -4978,7 +4979,16 @@ static void run_state_machine(struct tcpm_port *port)
>   		if (ret < 0)
>   			tcpm_set_state(port, SNK_UNATTACHED, 0);
>   		else
> -			tcpm_set_state(port, SNK_STARTUP, 0);
> +			/*
> +			 * For Type C port controllers that use Battery Charging
> +			 * Detection (based on BCv1.2 spec) to detect USB
> +			 * charger type, add a delay of "snk_bc12_cmpletion_time"
> +			 * before transitioning to SNK_STARTUP to allow BC1.2
> +			 * detection to complete before PD is eventually enabled
> +			 * in later states.
> +			 */
> +			tcpm_set_state(port, SNK_STARTUP,
> +				       port->timings.snk_bc12_cmpletion_time);
>   		break;
>   	case SNK_STARTUP:
>   		opmode =  tcpm_get_pwr_opmode(port->polarity ?
> @@ -7090,6 +7100,10 @@ static void tcpm_fw_get_timings(struct tcpm_port *port, struct fwnode_handle *fw
>   		port->timings.cc_debounce_time = val;
>   	else
>   		port->timings.cc_debounce_time = PD_T_CC_DEBOUNCE;
> +
> +	ret = fwnode_property_read_u32(fwnode, "sink-bc12-completion-time-ms", &val);
> +	if (!ret)
> +		port->timings.snk_bc12_cmpletion_time = val;
>   }
>   
>   static int tcpm_fw_get_caps(struct tcpm_port *port, struct fwnode_handle *fwnode)


I wanted to gently follow up with you on this patchset if this looks 
okay to you?


Thanks,

Amit