[RFC] usb: typec: tcpm: remove operating_snk_mw for rdo

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 17-04-18 08:01, Li Jun wrote:
> This patch is a further update for rdo based on [1], which
> removed max_snk_ma/mv/mw but kept operating_snk_mw.
> operating_snk_mw is only used to judge capability mismatch,
> per PD spec, we can achieve this via compare the selected
> source PDO and matching sink PDO, also after patch [1], we
> don't limit the PDO matching between the same type, so the
> rdo operating and max current/power calculation should be
> updated accordingly.

I do not believe that this is correct, lets take a device
with a fusb302 tcpc with the following PDO-s:

	PDO_FIXED(5000, 400, PDO_FIXED_FLAGS)
	PDO_VAR(5000, 12000, 3000);

And an operating_snk_mw of 2500mW then according to your
new code a charger which supplies 12V 2A will now get
the mismatch bit set even though it is delivering 24W.

I really don't see any way to fix this and I believe we
should just keep the operating_snk_mw field.

Regards

Hans



> [1]https://patchwork.kernel.org/patch/10342299/
> 
> Signed-off-by: Li Jun <jun.li@nxp.com>
> ---
>   drivers/usb/typec/tcpm.c | 52 ++++++++++++++++++++++++++++++------------------
>   1 file changed, 33 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
> index 27192083..0be04b3 100644
> --- a/drivers/usb/typec/tcpm.c
> +++ b/drivers/usb/typec/tcpm.c
> @@ -1854,28 +1854,42 @@ static int tcpm_pd_build_request(struct tcpm_port *port, u32 *rdo)
>   	else
>   		mv = pdo_min_voltage(pdo);
>   
> -	/* Select maximum available current within the sink pdo's limit */
> -	if (type == PDO_TYPE_BATT) {
> -		mw = min_power(pdo, matching_snk_pdo);
> -		ma = 1000 * mw / mv;
> -	} else {
> -		ma = min_current(pdo, matching_snk_pdo);
> -		mw = ma * mv / 1000;
> -	}
> -
>   	flags = RDO_USB_COMM | RDO_NO_SUSPEND;
>   
> -	/* Set mismatch bit if offered power is less than operating power */
> -	max_ma = ma;
> -	max_mw = mw;
> -	if (mw < port->operating_snk_mw) {
> -		flags |= RDO_CAP_MISMATCH;
> -		if (type == PDO_TYPE_BATT &&
> -		    (pdo_max_power(matching_snk_pdo) > pdo_max_power(pdo)))
> -			max_mw = pdo_max_power(matching_snk_pdo);
> -		else if (pdo_max_current(matching_snk_pdo) >
> -			 pdo_max_current(pdo))
> +	switch (type) {
> +	case PDO_TYPE_FIXED:
> +	case PDO_TYPE_VAR:
> +		if (pdo_type(matching_snk_pdo) == PDO_TYPE_BATT)
> +			max_ma = pdo_max_power(matching_snk_pdo) * 1000 / mv;
> +		else
>   			max_ma = pdo_max_current(matching_snk_pdo);
> +
> +		if (max_ma > pdo_max_current(pdo)) {
> +			flags |= RDO_CAP_MISMATCH;
> +			ma = pdo_max_current(pdo);
> +		} else {
> +			ma = max_ma;
> +		}
> +		break;
> +	case PDO_TYPE_BATT:
> +		if (pdo_type(matching_snk_pdo) == PDO_TYPE_BATT)
> +			max_mw = pdo_max_power(matching_snk_pdo);
> +		else
> +			max_mw = pdo_max_current(matching_snk_pdo) *
> +				 pdo_min_voltage(matching_snk_pdo) /
> +				 1000;
> +
> +		if (max_mw > pdo_max_power(pdo)) {
> +			flags |= RDO_CAP_MISMATCH;
> +			mw = pdo_max_power(pdo);
> +		} else {
> +			mw = max_mw;
> +		}
> +
> +		ma = mw * 1000 / mv;
> +		break;
> +	default:
> +		break;
>   	}
>   
>   	tcpm_log(port, "cc=%d cc1=%d cc2=%d vbus=%d vconn=%s polarity=%d",
>
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