linux-kernel - Re: [PATCH 2/2] usb: typec: fusb302: Resolve fixed power role contract setup

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Message-ID: <20180926163013.GB17716@roeck-us.net>
Date:   Wed, 26 Sep 2018 09:30:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.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,
        support.opensource@...semi.com
Subject: Re: [PATCH 2/2] usb: typec: fusb302: Resolve fixed power role
 contract setup

On Wed, Sep 26, 2018 at 04:23:52PM +0100, Adam Thomson wrote:
> When the controller is configured for a fixed power role (Source
> only or Sink only), attach does not proceed within the TCPM state
> machine as there is no CC event generated by this driver to update
> the CC line status.
> 
> To rectify this, when CC is configured as Source or Sink we now
> make use of the hardware's automatic fixed Source or Sink
> toggling mechanism, which detects attaches in the same way as for
> DRP toggling. In this way the result of toggling is handled in the
> same way by the 'fusb302_handle_togdone()' function, and CC events
> are generated as expected for TCPM allowing a contract to be
> established.
> 
> Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>

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

> ---
>  drivers/usb/typec/tcpm/fusb302.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
> index fd851d8..43b64d9 100644
> --- a/drivers/usb/typec/tcpm/fusb302.c
> +++ b/drivers/usb/typec/tcpm/fusb302.c
> @@ -679,6 +679,7 @@ static int tcpm_set_cc(struct tcpc_dev *dev, enum typec_cc_status cc)
>  	int ret = 0;
>  	bool pull_up, pull_down;
>  	u8 rd_mda;
> +	enum toggling_mode mode;
>  
>  	mutex_lock(&chip->lock);
>  	switch (cc) {
> @@ -764,6 +765,29 @@ static int tcpm_set_cc(struct tcpc_dev *dev, enum typec_cc_status cc)
>  		chip->intr_comp_chng = false;
>  	}
>  	fusb302_log(chip, "cc := %s", typec_cc_status_name[cc]);
> +
> +	/* Enable detection for fixed SNK or SRC only roles */
> +	switch (cc) {
> +	case TYPEC_CC_RD:
> +		mode = TOGGLING_MODE_SNK;
> +		break;
> +	case TYPEC_CC_RP_DEF:
> +	case TYPEC_CC_RP_1_5:
> +	case TYPEC_CC_RP_3_0:
> +		mode = TOGGLING_MODE_SRC;
> +		break;
> +	default:
> +		mode = TOGGLING_MODE_OFF;
> +		break;
> +	}
> +
> +	if (mode != TOGGLING_MODE_OFF) {
> +		ret = fusb302_set_toggling(chip, mode);
> +		if (ret < 0)
> +			fusb302_log(chip,
> +				    "cannot set fixed role toggling mode, ret=%d",
> +				    ret);
> +	}
>  done:
>  	mutex_unlock(&chip->lock);
>  
> -- 
> 1.9.1
>