linux-kernel - Re: [PATCH v2] usb: typec: fusb302: Fix masking of comparator and bc

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Date:   Mon, 8 Nov 2021 12:24:51 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Ondrej Jirman <megous@...ous.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        "open list:USB TYPEC PORT CONTROLLER DRIVERS" 
        <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: typec: fusb302: Fix masking of comparator and
 bc_lvl interrupts

Hi,

On 11/8/21 11:28, Ondrej Jirman wrote:
> The code that enables either BC_LVL or COMP_CHNG interrupt in tcpm_set_cc
> wrongly assumes that the interrupt is unmasked by writing 1 to the apropriate
> bit in the mask register. In fact, interrupts are enabled when the mask
> is 0, so the tcpm_set_cc enables interrupt for COMP_CHNG when it expects
> BC_LVL interrupt to be enabled.
> 
> This causes inability of the driver to recognize cable unplug events
> in host mode (unplug is recognized only via a COMP_CHNG interrupt).
> 
> In device mode this bug was masked by simultaneous triggering of the VBUS
> change interrupt, because of loss of VBUS when the port peer is providing
> power.
> 
> Fixes: 48242e30532b ("usb: typec: fusb302: Revert "Resolve fixed power role contract setup"")
> Signed-off-by: Ondrej Jirman <megous@...ous.com>
> Cc: Hans de Goede <hdegoede@...hat.com>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans

> ---
>  drivers/usb/typec/tcpm/fusb302.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
> index 7a2a17866a823..72f9001b07921 100644
> --- a/drivers/usb/typec/tcpm/fusb302.c
> +++ b/drivers/usb/typec/tcpm/fusb302.c
> @@ -669,25 +669,27 @@ static int tcpm_set_cc(struct tcpc_dev *dev, enum typec_cc_status cc)
>  		ret = fusb302_i2c_mask_write(chip, FUSB_REG_MASK,
>  					     FUSB_REG_MASK_BC_LVL |
>  					     FUSB_REG_MASK_COMP_CHNG,
> -					     FUSB_REG_MASK_COMP_CHNG);
> +					     FUSB_REG_MASK_BC_LVL);
>  		if (ret < 0) {
>  			fusb302_log(chip, "cannot set SRC interrupt, ret=%d",
>  				    ret);
>  			goto done;
>  		}
>  		chip->intr_comp_chng = true;


> +		chip->intr_bc_lvl = false;

FWIW this is not necessary because the fusb302_set_toggling(chip, TOGGLING_MODE_OFF)
already does this, but it makes the code more clear, so lets keep it.

>  		break;
>  	case TYPEC_CC_RD:
>  		ret = fusb302_i2c_mask_write(chip, FUSB_REG_MASK,
>  					     FUSB_REG_MASK_BC_LVL |
>  					     FUSB_REG_MASK_COMP_CHNG,
> -					     FUSB_REG_MASK_BC_LVL);
> +					     FUSB_REG_MASK_COMP_CHNG);
>  		if (ret < 0) {
>  			fusb302_log(chip, "cannot set SRC interrupt, ret=%d",
>  				    ret);
>  			goto done;
>  		}
>  		chip->intr_bc_lvl = true;


> +		chip->intr_comp_chng = false;

Idem.

>  		break;
>  	default:
>  		break;
> 

Regards,

Hans