On Fri, Aug 15, 2025 at 11:31:51AM -0700, Amit Sunil Dhamne via B4 Relay wrote:
> From: Amit Sunil Dhamne <amitsd@xxxxxxxxxx>
>
> Low power mode is enabled when reading CC resistance as part of
> `max_contaminant_read_resistance_kohm()` and left in that state.
> However, it's supposed to work with 1uA current source. To read CC
> comparator values current source is changed to 80uA. This causes a storm
> of CC interrupts as it (falsely) detects a potential contaminant. To
> prevent this, disable low power mode current sourcing before reading
> comparator values.
>
> Fixes: 02b332a06397 ("usb: typec: maxim_contaminant: Implement check_contaminant callback")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Amit Sunil Dhamne <amitsd@xxxxxxxxxx>
> Reviewed-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> drivers/usb/typec/tcpm/maxim_contaminant.c | 5 +++++
> drivers/usb/typec/tcpm/tcpci_maxim.h | 1 +
> 2 files changed, 6 insertions(+)
>
> diff --git a/drivers/usb/typec/tcpm/maxim_contaminant.c b/drivers/usb/typec/tcpm/maxim_contaminant.c
> index 0cdda06592fd3cc34e2179ccd49ef677f8ec9792..818cfe226ac7716de2fcbce205c67ea16acba592 100644
> --- a/drivers/usb/typec/tcpm/maxim_contaminant.c
> +++ b/drivers/usb/typec/tcpm/maxim_contaminant.c
> @@ -188,6 +188,11 @@ static int max_contaminant_read_comparators(struct max_tcpci_chip *chip, u8 *ven
> if (ret < 0)
> return ret;
>
> + /* Disable low power mode */
> + ret = regmap_update_bits(regmap, TCPC_VENDOR_CC_CTRL2, CCLPMODESEL,
> + FIELD_PREP(CCLPMODESEL,
> + LOW_POWER_MODE_DISABLE));
> +
> /* Sleep to allow comparators settle */
> usleep_range(5000, 6000);
> ret = regmap_update_bits(regmap, TCPC_TCPC_CTRL, TCPC_TCPC_CTRL_ORIENTATION, PLUG_ORNT_CC1);
> diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.h b/drivers/usb/typec/tcpm/tcpci_maxim.h
> index 76270d5c283880dc49b13cabe7d682f2c2bf15fe..b33540a42a953dc6d8197790ee4af3b6f52791ce 100644
> --- a/drivers/usb/typec/tcpm/tcpci_maxim.h
> +++ b/drivers/usb/typec/tcpm/tcpci_maxim.h
> @@ -21,6 +21,7 @@
> #define CCOVPDIS BIT(6)
> #define SBURPCTRL BIT(5)
> #define CCLPMODESEL GENMASK(4, 3)
> +#define LOW_POWER_MODE_DISABLE 0
> #define ULTRA_LOW_POWER_MODE 1
> #define CCRPCTRL GENMASK(2, 0)
> #define UA_1_SRC 1
>
> --
> 2.51.0.rc1.167.g924127e9c0-goog
>
--
heikki
