Re: [PATCH] usb: typec: tcpm/tcpci_maxim: fix non-contaminant CC handling

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi André,

On Wed, Jul 10, 2024 at 07:28:32AM +0100, André Draszik wrote:
> tcpci_maxim currently never triggers the TCPM state machine when CC
> status has not changed due to a contaminant but due to a real
> connection event, i.e. a genuine plug event, meaning the system will
> stay idle and not notify any subscribers.
> 
> The reason is that the initial state of the port is 'toggling', which
> causes _max_tcpci_irq() to only drive the contamination part of the
> TCPM state machine (via tcpm_port_clean()).
> 
> What should happen instead is that if no contamination was detected,
> the TCPM should be notified of the CC change in this case.
> 
> To fix this, we update ...is_contaminant() to also allow its caller to
> determine if more CC processing is required and then call into the TCPM
> as required.
> 
> While at it, add a kernel-doc for max_contaminant_is_contaminant().
> 
> Note: the code has an issue where I2C errors during contaminant
> detection also cause the TCPM state machine to not be updated. This
> commit doesn't change this behaviour and should be addressed by
> follow-up commit(s).

This looks okay to me, but just in case, let's wait for comments from
Badhri, or maybe RD can take a look at this. One nitpick below.

> Signed-off-by: André Draszik <andre.draszik@linaro.org>
> ---
>  drivers/usb/typec/tcpm/maxim_contaminant.c |  7 +++++--
>  drivers/usb/typec/tcpm/tcpci_maxim.h       | 15 ++++++++++++++-
>  drivers/usb/typec/tcpm/tcpci_maxim_core.c  | 12 ++++++++----
>  3 files changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/maxim_contaminant.c b/drivers/usb/typec/tcpm/maxim_contaminant.c
> index f8504a90da26..e7fa3e36f8ae 100644
> --- a/drivers/usb/typec/tcpm/maxim_contaminant.c
> +++ b/drivers/usb/typec/tcpm/maxim_contaminant.c
> @@ -322,11 +322,14 @@ static int max_contaminant_enable_dry_detection(struct max_tcpci_chip *chip)
>  	return 0;
>  }
>  
> -bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce)
> +bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce,
> +				    bool *cc_handled)
>  {
>  	u8 cc_status, pwr_cntl;
>  	int ret;
>  
> +	*cc_handled = true;
> +
>  	ret = max_tcpci_read8(chip, TCPC_CC_STATUS, &cc_status);
>  	if (ret < 0)
>  		return false;
> @@ -368,7 +371,6 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
>  				return true;
>  			}
>  		}
> -		return false;
>  	} else if (chip->contaminant_state == DETECTED) {
>  		if (STATUS_CHECK(cc_status, TCPC_CC_STATUS_TOGGLING, 0)) {
>  			chip->contaminant_state = max_contaminant_detect_contaminant(chip);
> @@ -379,6 +381,7 @@ bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect
>  		}
>  	}
>  
> +	*cc_handled = false;
>  	return false;
>  }
>  
> diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.h b/drivers/usb/typec/tcpm/tcpci_maxim.h
> index 78ff3b73ee7e..9c7f714d2c21 100644
> --- a/drivers/usb/typec/tcpm/tcpci_maxim.h
> +++ b/drivers/usb/typec/tcpm/tcpci_maxim.h
> @@ -85,6 +85,19 @@ static inline int max_tcpci_write8(struct max_tcpci_chip *chip, unsigned int reg
>  	return regmap_raw_write(chip->data.regmap, reg, &val, sizeof(u8));
>  }
>  
> -bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce);
> +/**
> + * max_contaminant_is_contaminant - Test if CC was toggled due to contaminant
> + *
> + * @chip: Handle to a struct max_tcpci_chip
> + * @disconnect_while_debounce: Whether or not to sleep as debouncing measure
> + * @cc_handled: Returns whether or not CC toggling was handled here
> + *
> + * Determine if a contaminant was detected.
> + *
> + * Returns: true if a contaminant was detected, false otherwise. cc_handled
> + * is updated to reflect whether or not further CC handling is required.
> + */
> +bool max_contaminant_is_contaminant(struct max_tcpci_chip *chip, bool disconnect_while_debounce,
> +				    bool *cc_handled);
>  
>  #endif  // TCPCI_MAXIM_H_
> diff --git a/drivers/usb/typec/tcpm/tcpci_maxim_core.c b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> index eec3bcec119c..55d931672ecd 100644
> --- a/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> +++ b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
> @@ -357,12 +357,15 @@ static irqreturn_t _max_tcpci_irq(struct max_tcpci_chip *chip, u16 status)
>  		tcpm_vbus_change(chip->port);
>  
>  	if (status & TCPC_ALERT_CC_STATUS) {
> +		bool cc_handled = false; /* CC toggle handled by contaminant detection */
> +
>  		if (chip->contaminant_state == DETECTED || tcpm_port_is_toggling(chip->port)) {
> -			if (!max_contaminant_is_contaminant(chip, false))
> +			if (!max_contaminant_is_contaminant(chip, false,
> +							    &cc_handled))

One line is enough for that.

>  				tcpm_port_clean(chip->port);
> -		} else {
> -			tcpm_cc_change(chip->port);
>  		}
> +		if (!cc_handled)
> +			tcpm_cc_change(chip->port);
>  	}
>  
>  	if (status & TCPC_ALERT_POWER_STATUS)
> @@ -455,8 +458,9 @@ static int tcpci_init(struct tcpci *tcpci, struct tcpci_data *data)
>  static void max_tcpci_check_contaminant(struct tcpci *tcpci, struct tcpci_data *tdata)
>  {
>  	struct max_tcpci_chip *chip = tdata_to_max_tcpci(tdata);
> +	bool cc_handled;
>  
> -	if (!max_contaminant_is_contaminant(chip, true))
> +	if (!max_contaminant_is_contaminant(chip, true, &cc_handled))
>  		tcpm_port_clean(chip->port);
>  }

thanks,

-- 
heikki