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Message-ID: <CAPTae5JRDA5UVdk0Y-Z6VistV_y7kcCZYgqYTbuuZAO+znWHvg@mail.gmail.com>
Date: Tue, 14 Jan 2025 21:06:36 -0800
From: Badhri Jagan Sridharan <badhri@...gle.com>
To: Kyle Tso <kyletso@...gle.com>
Cc: heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org,
andre.draszik@...aro.org, rdbabiera@...gle.com, m.felsch@...gutronix.de,
xu.yang_2@....com, u.kleine-koenig@...libre.com, emanuele.ghidoli@...adex.com,
amitsd@...gle.com, linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH v1] usb: typec: tcpci: Prevent Sink disconnection before
vPpsShutdown in SPR PPS
On Tue, Jan 14, 2025 at 6:25 AM Kyle Tso <kyletso@...gle.com> wrote:
>
> The Source can drop its output voltage to the minimum of the requested
> PPS APDO voltage range when it is in Current Limit Mode. If this voltage
> falls within the range of vPpsShutdown, the Source initiates a Hard
> Reset and discharges Vbus. However, currently the Sink may disconnect
> before the voltage reaches vPpsShutdown, leading to unexpected behavior.
>
> Prevent premature disconnection by setting the Sink's disconnect
> threshold to the minimum vPpsShutdown value. Additionally, consider the
> voltage drop due to IR drop when calculating the appropriate threshold.
> This ensures a robust and reliable interaction between the Source and
> Sink during SPR PPS Current Limit Mode operation.
>
> Fixes: 4288debeaa4e ("usb: typec: tcpci: Fix up sink disconnect thresholds for PD")
> Cc: stable@...r.kernel.org
> Signed-off-by: Kyle Tso <kyletso@...gle.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
> drivers/usb/typec/tcpm/tcpci.c | 13 +++++++++----
> drivers/usb/typec/tcpm/tcpm.c | 8 +++++---
> include/linux/usb/tcpm.h | 3 ++-
> 3 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpci.c b/drivers/usb/typec/tcpm/tcpci.c
> index 48762508cc86..19ab6647af70 100644
> --- a/drivers/usb/typec/tcpm/tcpci.c
> +++ b/drivers/usb/typec/tcpm/tcpci.c
> @@ -27,6 +27,7 @@
> #define VPPS_NEW_MIN_PERCENT 95
> #define VPPS_VALID_MIN_MV 100
> #define VSINKDISCONNECT_PD_MIN_PERCENT 90
> +#define VPPS_SHUTDOWN_MIN_PERCENT 85
>
> struct tcpci {
> struct device *dev;
> @@ -366,7 +367,8 @@ static int tcpci_enable_auto_vbus_discharge(struct tcpc_dev *dev, bool enable)
> }
>
> static int tcpci_set_auto_vbus_discharge_threshold(struct tcpc_dev *dev, enum typec_pwr_opmode mode,
> - bool pps_active, u32 requested_vbus_voltage_mv)
> + bool pps_active, u32 requested_vbus_voltage_mv,
> + u32 apdo_min_voltage_mv)
> {
> struct tcpci *tcpci = tcpc_to_tcpci(dev);
> unsigned int pwr_ctrl, threshold = 0;
> @@ -388,9 +390,12 @@ static int tcpci_set_auto_vbus_discharge_threshold(struct tcpc_dev *dev, enum ty
> threshold = AUTO_DISCHARGE_DEFAULT_THRESHOLD_MV;
> } else if (mode == TYPEC_PWR_MODE_PD) {
> if (pps_active)
> - threshold = ((VPPS_NEW_MIN_PERCENT * requested_vbus_voltage_mv / 100) -
> - VSINKPD_MIN_IR_DROP_MV - VPPS_VALID_MIN_MV) *
> - VSINKDISCONNECT_PD_MIN_PERCENT / 100;
> + /*
> + * To prevent disconnect when the source is in Current Limit Mode.
> + * Set the threshold to the lowest possible voltage vPpsShutdown (min)
> + */
> + threshold = VPPS_SHUTDOWN_MIN_PERCENT * apdo_min_voltage_mv / 100 -
> + VSINKPD_MIN_IR_DROP_MV;
> else
> threshold = ((VSRC_NEW_MIN_PERCENT * requested_vbus_voltage_mv / 100) -
> VSINKPD_MIN_IR_DROP_MV - VSRC_VALID_MIN_MV) *
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 460dbde9fe22..e4b85a09c3ae 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -2973,10 +2973,12 @@ static int tcpm_set_auto_vbus_discharge_threshold(struct tcpm_port *port,
> return 0;
>
> ret = port->tcpc->set_auto_vbus_discharge_threshold(port->tcpc, mode, pps_active,
> - requested_vbus_voltage);
> + requested_vbus_voltage,
> + port->pps_data.min_volt);
> tcpm_log_force(port,
> - "set_auto_vbus_discharge_threshold mode:%d pps_active:%c vbus:%u ret:%d",
> - mode, pps_active ? 'y' : 'n', requested_vbus_voltage, ret);
> + "set_auto_vbus_discharge_threshold mode:%d pps_active:%c vbus:%u pps_apdo_min_volt:%u ret:%d",
> + mode, pps_active ? 'y' : 'n', requested_vbus_voltage,
> + port->pps_data.min_volt, ret);
>
> return ret;
> }
> diff --git a/include/linux/usb/tcpm.h b/include/linux/usb/tcpm.h
> index 061da9546a81..b22e659f81ba 100644
> --- a/include/linux/usb/tcpm.h
> +++ b/include/linux/usb/tcpm.h
> @@ -163,7 +163,8 @@ struct tcpc_dev {
> void (*frs_sourcing_vbus)(struct tcpc_dev *dev);
> int (*enable_auto_vbus_discharge)(struct tcpc_dev *dev, bool enable);
> int (*set_auto_vbus_discharge_threshold)(struct tcpc_dev *dev, enum typec_pwr_opmode mode,
> - bool pps_active, u32 requested_vbus_voltage);
> + bool pps_active, u32 requested_vbus_voltage,
> + u32 pps_apdo_min_voltage);
> bool (*is_vbus_vsafe0v)(struct tcpc_dev *dev);
> void (*set_partner_usb_comm_capable)(struct tcpc_dev *dev, bool enable);
> void (*check_contaminant)(struct tcpc_dev *dev);
> --
> 2.47.1.688.g23fc6f90ad-goog
>
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