Re: [PATCH 2/2] usb: typec: maxim_contaminant: re-enable cc toggle if cc is open and port is clean

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Aug 14, 2025 at 07:34:10PM -0700, Amit Sunil Dhamne via B4 Relay wrote:
> From: Amit Sunil Dhamne <amitsd@google.com>
> 
> Presently in `max_contaminant_is_contaminant()` if there's no
> contaminant detected previously, CC is open & stopped toggling and no
> contaminant is currently present, TCPC.RC would be programmed to do DRP
> toggling. However, it didn't actively look for a connection. This would
> lead to Type-C not detect *any* new connections. Hence, in the above
> situation, re-enable toggling & program TCPC to look for a new
> connection.
> 
> Also, return early if TCPC was looking for connection as this indicates
> TCPC has neither detected a potential connection nor a change in
> contaminant state.
> 
> In addition, once dry detection is complete (port is dry), restart
> toggling.
> 
> Fixes: 02b332a06397e ("usb: typec: maxim_contaminant: Implement check_contaminant callback")
> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
> Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
> ---
>  drivers/usb/typec/tcpm/maxim_contaminant.c | 53 ++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/maxim_contaminant.c b/drivers/usb/typec/tcpm/maxim_contaminant.c
> index 818cfe226ac7716de2fcbce205c67ea16acba592..af8da6dc60ae0bc5900f6614514d51f41eded8ab 100644
> --- a/drivers/usb/typec/tcpm/maxim_contaminant.c
> +++ b/drivers/usb/typec/tcpm/maxim_contaminant.c
> @@ -329,6 +329,39 @@ static int max_contaminant_enable_dry_detection(struct max_tcpci_chip *chip)
>  	return 0;
>  }
>  
> +static int max_contaminant_enable_toggling(struct max_tcpci_chip *chip)
> +{
> +	struct regmap *regmap = chip->data.regmap;
> +	int ret;
> +
> +	/* Disable dry detection if enabled. */
> +	ret = regmap_update_bits(regmap, TCPC_VENDOR_CC_CTRL2, CCLPMODESEL,
> +				 FIELD_PREP(CCLPMODESEL,
> +					    LOW_POWER_MODE_DISABLE));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_update_bits(regmap, TCPC_VENDOR_CC_CTRL1, CCCONNDRY, 0);
> +	if (ret)
> +		return ret;
> +
> +	ret = max_tcpci_write8(chip, TCPC_ROLE_CTRL, TCPC_ROLE_CTRL_DRP |
> +			       FIELD_PREP(TCPC_ROLE_CTRL_CC1,
> +					  TCPC_ROLE_CTRL_CC_RD) |
> +			       FIELD_PREP(TCPC_ROLE_CTRL_CC2,
> +					  TCPC_ROLE_CTRL_CC_RD));
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_update_bits(regmap, TCPC_TCPC_CTRL,
> +				 TCPC_TCPC_CTRL_EN_LK4CONN_ALRT,
> +				 TCPC_TCPC_CTRL_EN_LK4CONN_ALRT);
> +	if (ret)
> +		return ret;
> +
> +	return max_tcpci_write8(chip, TCPC_COMMAND, TCPC_CMD_LOOK4CONNECTION);
> +}
> +
>  bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce,
>  				    bool *cc_handled)
>  {
> @@ -345,6 +378,12 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
>  	if (ret < 0)
>  		return false;
>  
> +	if (cc_status & TCPC_CC_STATUS_TOGGLING) {
> +		if (chip->contaminant_state == DETECTED)
> +			return true;
> +		return false;
> +	}
> +
>  	if (chip->contaminant_state == NOT_DETECTED || chip->contaminant_state == SINK) {
>  		if (!disconnect_while_debounce)
>  			msleep(100);
> @@ -377,6 +416,12 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
>  				max_contaminant_enable_dry_detection(chip);
>  				return true;
>  			}
> +
> +			ret = max_contaminant_enable_toggling(chip);
> +			if (ret)
> +				dev_err(chip->dev,
> +					"Failed to enable toggling, ret=%d",
> +					ret);
>  		}
>  	} else if (chip->contaminant_state == DETECTED) {
>  		if (!(cc_status & TCPC_CC_STATUS_TOGGLING)) {
> @@ -384,6 +429,14 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
>  			if (chip->contaminant_state == DETECTED) {
>  				max_contaminant_enable_dry_detection(chip);
>  				return true;
> +			} else {
> +				ret = max_contaminant_enable_toggling(chip);
> +				if (ret) {
> +					dev_err(chip->dev,
> +						"Failed to enable toggling, ret=%d",
> +						ret);
> +					return true;
> +				}
>  			}
>  		}
>  	}
> 
> -- 
> 2.51.0.rc1.167.g924127e9c0-goog
> 
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>