[PATCH v3 1/3] usb: typec: tcpm: Honour pSnkStdby requirement during negotiation

[PATCH v3 1/3] usb: typec: tcpm: Honour pSnkStdby requirement during negotiation

[Badhri Jagan Sridharan]

From PD Spec:
The Sink Shall transition to Sink Standby before a positive or
negative voltage transition of VBUS. During Sink Standby
the Sink Shall reduce its power draw to pSnkStdby. This allows
the Source to manage the voltage transition as well as
supply sufficient operating current to the Sink to maintain PD
operation during the transition. The Sink Shall
complete this transition to Sink Standby within tSnkStdby
after evaluating the Accept Message from the Source. The
transition when returning to Sink operation from Sink Standby
Shall be completed within tSnkNewPower. The
pSnkStdby requirement Shall only apply if the Sink power draw
is higher than this level.

The above requirement needs to be met to prevent hard resets
from port partner.

Without the patch: (5V/3A during SNK_DISCOVERY all the way through
explicit contract)
[   95.711984] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
[   95.712007] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[   95.712017] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
[   95.837190] VBUS on
[   95.882075] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
[   95.882082] state change SNK_DEBOUNCED -> SNK_ATTACHED [rev3 NONE_AMS]
[   95.882086] polarity 1
[   95.883151] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:5000 ret:0
[   95.883441] enable vbus discharge ret:0
[   95.883445] Requesting mux state 1, usb-role 2, orientation 2
[   95.883776] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
[   95.883879] pending state change SNK_STARTUP -> SNK_DISCOVERY @ 500 ms [rev3 NONE_AMS]
[   96.038960] VBUS on
[   96.383939] state change SNK_STARTUP -> SNK_DISCOVERY [delayed 500 ms]
[   96.383946] Setting voltage/current limit 5000 mV 3000 mA
[   96.383961] vbus=0 charge:=1
[   96.386044] state change SNK_DISCOVERY -> SNK_WAIT_CAPABILITIES [rev3 NONE_AMS]
[   96.386309] pending state change SNK_WAIT_CAPABILITIES -> HARD_RESET_SEND @ 450 ms [rev3 NONE_AMS]
[   96.394404] PD RX, header: 0x2161 [1]
[   96.394408]  PDO 0: type 0, 5000 mV, 3000 mA [E]
[   96.394410]  PDO 1: type 0, 9000 mV, 2000 mA []
[   96.394412] state change SNK_WAIT_CAPABILITIES -> SNK_NEGOTIATE_CAPABILITIES [rev2 POWER_NEGOTIATION]
[   96.394416] Setting usb_comm capable false
[   96.395083] cc=0 cc1=0 cc2=5 vbus=0 vconn=sink polarity=1
[   96.395089] Requesting PDO 1: 9000 mV, 2000 mA
[   96.395093] PD TX, header: 0x1042
[   96.397404] PD TX complete, status: 0
[   96.397424] pending state change SNK_NEGOTIATE_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev2 POWER_NEGOTIATION]
[   96.400826] PD RX, header: 0x363 [1]
[   96.400829] state change SNK_NEGOTIATE_CAPABILITIES -> SNK_TRANSITION_SINK [rev2 POWER_NEGOTIATION]
[   96.400832] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 500 ms [rev2 POWER_NEGOTIATION]
[   96.577315] PD RX, header: 0x566 [1]
[   96.577321] Setting voltage/current limit 9000 mV 2000 mA
[   96.578363] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9000 ret:0
[   96.578370] state change SNK_TRANSITION_SINK -> SNK_READY [rev2 POWER_NEGOTIATION]

With the patch:
[  168.398573] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
[  168.398605] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
[  168.398619] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
[  168.522348] VBUS on
[  168.568676] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
[  168.568684] state change SNK_DEBOUNCED -> SNK_ATTACHED [rev3 NONE_AMS]
[  168.568688] polarity 1
[  168.569867] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:5000 ret:0
[  168.570158] enable vbus discharge ret:0
[  168.570161] Requesting mux state 1, usb-role 2, orientation 2
[  168.570504] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
[  168.570634] pending state change SNK_STARTUP -> SNK_DISCOVERY @ 500 ms [rev3 NONE_AMS]
[  169.070689] state change SNK_STARTUP -> SNK_DISCOVERY [delayed 500 ms]
[  169.070695] Setting voltage/current limit 5000 mV 3000 mA
[  169.070702] vbus=0 charge:=1
[  169.072719] state change SNK_DISCOVERY -> SNK_WAIT_CAPABILITIES [rev3 NONE_AMS]
[  169.073145] pending state change SNK_WAIT_CAPABILITIES -> HARD_RESET_SEND @ 450 ms [rev3 NONE_AMS]
[  169.077162] PD RX, header: 0x2161 [1]
[  169.077172]  PDO 0: type 0, 5000 mV, 3000 mA [E]
[  169.077178]  PDO 1: type 0, 9000 mV, 2000 mA []
[  169.077183] state change SNK_WAIT_CAPABILITIES -> SNK_NEGOTIATE_CAPABILITIES [rev2 POWER_NEGOTIATION]
[  169.077191] Setting usb_comm capable false
[  169.077753] cc=0 cc1=0 cc2=5 vbus=0 vconn=sink polarity=1
[  169.077759] Requesting PDO 1: 9000 mV, 2000 mA
[  169.077762] PD TX, header: 0x1042
[  169.079990] PD TX complete, status: 0
[  169.080013] pending state change SNK_NEGOTIATE_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev2 POWER_NEGOTIATION]
[  169.083183] VBUS on
[  169.084195] PD RX, header: 0x363 [1]
[  169.084200] state change SNK_NEGOTIATE_CAPABILITIES -> SNK_TRANSITION_SINK [rev2 POWER_NEGOTIATION]
[  169.084206] Setting standby current 5000 mV @ 500 mA
[  169.084209] Setting voltage/current limit 5000 mV 500 mA
[  169.084220] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 500 ms [rev2 POWER_NEGOTIATION]
[  169.260222] PD RX, header: 0x566 [1]
[  169.260227] Setting voltage/current limit 9000 mV 2000 mA
[  169.261315] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9000 ret:0
[  169.261321] state change SNK_TRANSITION_SINK -> SNK_READY [rev2 POWER_NEGOTIATION]
[  169.261570] AMS POWER_NEGOTIATION finished

Fixes: f0690a25a140b ("staging: typec: USB Type-C Port Manager (tcpm)")
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
---
Changes since V2:
* Refactored code based on Heikki's suggestion
* Added reviewed-by tag from Guenter
---
 drivers/usb/typec/tcpm/tcpm.c | 17 +++++++++++++++++
 include/linux/usb/pd.h        |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 1c32bdf62852..aedc8bb9532a 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -4131,6 +4131,23 @@ static void run_state_machine(struct tcpm_port *port)
 		}
 		break;
 	case SNK_TRANSITION_SINK:
+		/* From the USB PD spec:
+		 * "The Sink Shall transition to Sink Standby before a positive or
+		 * negative voltage transition of VBUS. During Sink Standby
+		 * the Sink Shall reduce its power draw to pSnkStdby."
+		 *
+		 * This is not applicable to PPS though as the port can continue
+		 * to draw negotiated power without switching to standby.
+		 */
+		if (port->supply_voltage != port->req_supply_voltage && !port->pps_data.active &&
+		    port->current_limit * port->supply_voltage / 1000 > PD_P_SNK_STDBY_MW) {
+			u32 stdby_ma = PD_P_SNK_STDBY_MW * 1000 / port->supply_voltage;
+
+			tcpm_log(port, "Setting standby current %u mV @ %u mA",
+				 port->supply_voltage, stdby_ma);
+			tcpm_set_current_limit(port, stdby_ma, port->supply_voltage);
+		}
+		fallthrough;
 	case SNK_TRANSITION_SINK_VBUS:
 		tcpm_set_state(port, hard_reset_state(port),
 			       PD_T_PS_TRANSITION);
diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
index 70d681918d01..bf00259493e0 100644
--- a/include/linux/usb/pd.h
+++ b/include/linux/usb/pd.h
@@ -493,4 +493,6 @@ static inline unsigned int rdo_max_power(u32 rdo)
 #define PD_N_CAPS_COUNT		(PD_T_NO_RESPONSE / PD_T_SEND_SOURCE_CAP)
 #define PD_N_HARD_RESET_COUNT	2
 
+#define PD_P_SNK_STDBY_MW	2500	/* 2500 mW */
+
 #endif /* __LINUX_USB_PD_H */
-- 
2.31.1.295.g9ea45b61b8-goog

[PATCH v3 2/3] usb: typec: tcpm: Allow slow charging loops to comply to pSnkStby

[Badhri Jagan Sridharan]

When a PD charger advertising Rp-3.0 is connected to a sink port, the
sink port current limit would 3A, during SNK_DISCOVERY, till power
negotiation starts. Once the negotiation starts the power limit needs
to drop down to pSnkStby(500mA @ 5V) and to negotiated current limit
once the explicit contract is in place. Not all charging loops can ramp
up to 3A and drop down to 500mA within tSnkStdby which is 15ms. The port
partner might hard reset if tSnkStdby is not met.

To solve this problem, this patch introduces slow-charger-loop which
when set makes the port request PD_P_SNK_STDBY_MW upon entering
SNK_DISCOVERY(instead of 3A or the 1.5A during SNK_DISCOVERY) and the
actual currrent limit after RX of PD_CTRL_PSRDY for PD link or during
SNK_READY for non-pd link.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
---
Changes since V2:
* Refactored code based on Heikki's suggestion
---
 drivers/usb/typec/tcpm/tcpm.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index aedc8bb9532a..2ad5e14a6867 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -459,6 +459,12 @@ struct tcpm_port {
 	/* Auto vbus discharge status */
 	bool auto_vbus_discharge_enabled;
 
+	/*
+	 * When set, port requests PD_P_SNK_STDBY_MW upon entering SNK_DISCOVERY and
+	 * the actual currrent limit after RX of PD_CTRL_PSRDY for PD link,
+	 * SNK_READY for non-pd link.
+	 */
+	bool slow_charger_loop;
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *dentry;
 	struct mutex logbuffer_lock;	/* log buffer access lock */
@@ -4047,9 +4053,11 @@ static void run_state_machine(struct tcpm_port *port)
 		break;
 	case SNK_DISCOVERY:
 		if (port->vbus_present) {
-			tcpm_set_current_limit(port,
-					       tcpm_get_current_limit(port),
-					       5000);
+			u32 current_lim = tcpm_get_current_limit(port);
+
+			if (port->slow_charger_loop || (current_lim > PD_P_SNK_STDBY_MW / 5))
+				current_lim = PD_P_SNK_STDBY_MW / 5;
+			tcpm_set_current_limit(port, current_lim, 5000);
 			tcpm_set_charge(port, true);
 			tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
 			break;
@@ -4161,6 +4169,8 @@ static void run_state_machine(struct tcpm_port *port)
 			port->pwr_opmode = TYPEC_PWR_MODE_PD;
 		}
 
+		if (!port->pd_capable && port->slow_charger_loop)
+			tcpm_set_current_limit(port, tcpm_get_current_limit(port), 5000);
 		tcpm_swap_complete(port, 0);
 		tcpm_typec_connect(port);
 		mod_enable_frs_delayed_work(port, 0);
@@ -5763,6 +5773,7 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
 	port->typec_caps.type = ret;
 	port->port_type = port->typec_caps.type;
 
+	port->slow_charger_loop = fwnode_property_read_bool(fwnode, "slow-charger-loop");
 	if (port->port_type == TYPEC_PORT_SNK)
 		goto sink;
 
-- 
2.31.1.295.g9ea45b61b8-goog

[PATCH v3 3/3] dt-bindings:: connector: Add slow-charger-loop definition

[Badhri Jagan Sridharan]

Allows PMIC charger loops which are slow(i.e. cannot meet the
15ms deadline) to still comply to pSnkStby i.e Maximum power
that can be consumed by sink while in Sink Standby state as defined
in 7.4.2 Sink Electrical Parameters of USB Power Delivery Specification
Revision 3.0, Version 1.2.

This patch introduces slow-charger-loop which when set makes
the port request PD_P_SNK_STDBY_MW(2.5W i.e 500mA@5V) upon entering
SNK_DISCOVERY (instead of 3A or the 1.5A during SNK_DISCOVERY) and the
actual currrent limit after RX of PD_CTRL_PSRDY for PD link or during
SNK_READY for non-pd link.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
---
Changes since V2:
To address Rob's comments
* Updated commit and the binding description.
* Updated subject as well.
---
 .../devicetree/bindings/connector/usb-connector.yaml   | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
index b6daedd62516..32509b98142e 100644
--- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
+++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
@@ -197,6 +197,16 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     enum: [1, 2, 3]
 
+  slow-charger-loop:
+    description: Allows PMIC charger loops which are slow(i.e. cannot meet the 15ms deadline) to
+      still comply to pSnkStby i.e Maximum power that can be consumed by sink while in Sink Standby
+      state as defined in 7.4.2 Sink Electrical Parameters of USB Power Delivery Specification
+      Revision 3.0, Version 1.2. When the property is set, the port requests pSnkStby(2.5W -
+      5V@500mA) upon entering SNK_DISCOVERY(instead of 3A or the 1.5A, Rp current advertised, during
+      SNK_DISCOVERY) and the actual currrent limit after reception of PS_Ready for PD link or during
+      SNK_READY for non-pd link.
+    type: boolean
+
 required:
   - compatible
 
-- 
2.31.1.295.g9ea45b61b8-goog

Re: [PATCH v3 1/3] usb: typec: tcpm: Honour pSnkStdby requirement during negotiation

[Heikki Krogerus]

On Tue, Apr 13, 2021 at 07:39:58PM -0700, Badhri Jagan Sridharan wrote:
> >From PD Spec:
> The Sink Shall transition to Sink Standby before a positive or
> negative voltage transition of VBUS. During Sink Standby
> the Sink Shall reduce its power draw to pSnkStdby. This allows
> the Source to manage the voltage transition as well as
> supply sufficient operating current to the Sink to maintain PD
> operation during the transition. The Sink Shall
> complete this transition to Sink Standby within tSnkStdby
> after evaluating the Accept Message from the Source. The
> transition when returning to Sink operation from Sink Standby
> Shall be completed within tSnkNewPower. The
> pSnkStdby requirement Shall only apply if the Sink power draw
> is higher than this level.
> 
> The above requirement needs to be met to prevent hard resets
> from port partner.
> 
> Without the patch: (5V/3A during SNK_DISCOVERY all the way through
> explicit contract)
> [   95.711984] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [   95.712007] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [   95.712017] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
> [   95.837190] VBUS on
> [   95.882075] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
> [   95.882082] state change SNK_DEBOUNCED -> SNK_ATTACHED [rev3 NONE_AMS]
> [   95.882086] polarity 1
> [   95.883151] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:5000 ret:0
> [   95.883441] enable vbus discharge ret:0
> [   95.883445] Requesting mux state 1, usb-role 2, orientation 2
> [   95.883776] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
> [   95.883879] pending state change SNK_STARTUP -> SNK_DISCOVERY @ 500 ms [rev3 NONE_AMS]
> [   96.038960] VBUS on
> [   96.383939] state change SNK_STARTUP -> SNK_DISCOVERY [delayed 500 ms]
> [   96.383946] Setting voltage/current limit 5000 mV 3000 mA
> [   96.383961] vbus=0 charge:=1
> [   96.386044] state change SNK_DISCOVERY -> SNK_WAIT_CAPABILITIES [rev3 NONE_AMS]
> [   96.386309] pending state change SNK_WAIT_CAPABILITIES -> HARD_RESET_SEND @ 450 ms [rev3 NONE_AMS]
> [   96.394404] PD RX, header: 0x2161 [1]
> [   96.394408]  PDO 0: type 0, 5000 mV, 3000 mA [E]
> [   96.394410]  PDO 1: type 0, 9000 mV, 2000 mA []
> [   96.394412] state change SNK_WAIT_CAPABILITIES -> SNK_NEGOTIATE_CAPABILITIES [rev2 POWER_NEGOTIATION]
> [   96.394416] Setting usb_comm capable false
> [   96.395083] cc=0 cc1=0 cc2=5 vbus=0 vconn=sink polarity=1
> [   96.395089] Requesting PDO 1: 9000 mV, 2000 mA
> [   96.395093] PD TX, header: 0x1042
> [   96.397404] PD TX complete, status: 0
> [   96.397424] pending state change SNK_NEGOTIATE_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev2 POWER_NEGOTIATION]
> [   96.400826] PD RX, header: 0x363 [1]
> [   96.400829] state change SNK_NEGOTIATE_CAPABILITIES -> SNK_TRANSITION_SINK [rev2 POWER_NEGOTIATION]
> [   96.400832] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 500 ms [rev2 POWER_NEGOTIATION]
> [   96.577315] PD RX, header: 0x566 [1]
> [   96.577321] Setting voltage/current limit 9000 mV 2000 mA
> [   96.578363] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9000 ret:0
> [   96.578370] state change SNK_TRANSITION_SINK -> SNK_READY [rev2 POWER_NEGOTIATION]
> 
> With the patch:
> [  168.398573] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [  168.398605] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [  168.398619] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
> [  168.522348] VBUS on
> [  168.568676] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
> [  168.568684] state change SNK_DEBOUNCED -> SNK_ATTACHED [rev3 NONE_AMS]
> [  168.568688] polarity 1
> [  168.569867] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:5000 ret:0
> [  168.570158] enable vbus discharge ret:0
> [  168.570161] Requesting mux state 1, usb-role 2, orientation 2
> [  168.570504] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
> [  168.570634] pending state change SNK_STARTUP -> SNK_DISCOVERY @ 500 ms [rev3 NONE_AMS]
> [  169.070689] state change SNK_STARTUP -> SNK_DISCOVERY [delayed 500 ms]
> [  169.070695] Setting voltage/current limit 5000 mV 3000 mA
> [  169.070702] vbus=0 charge:=1
> [  169.072719] state change SNK_DISCOVERY -> SNK_WAIT_CAPABILITIES [rev3 NONE_AMS]
> [  169.073145] pending state change SNK_WAIT_CAPABILITIES -> HARD_RESET_SEND @ 450 ms [rev3 NONE_AMS]
> [  169.077162] PD RX, header: 0x2161 [1]
> [  169.077172]  PDO 0: type 0, 5000 mV, 3000 mA [E]
> [  169.077178]  PDO 1: type 0, 9000 mV, 2000 mA []
> [  169.077183] state change SNK_WAIT_CAPABILITIES -> SNK_NEGOTIATE_CAPABILITIES [rev2 POWER_NEGOTIATION]
> [  169.077191] Setting usb_comm capable false
> [  169.077753] cc=0 cc1=0 cc2=5 vbus=0 vconn=sink polarity=1
> [  169.077759] Requesting PDO 1: 9000 mV, 2000 mA
> [  169.077762] PD TX, header: 0x1042
> [  169.079990] PD TX complete, status: 0
> [  169.080013] pending state change SNK_NEGOTIATE_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev2 POWER_NEGOTIATION]
> [  169.083183] VBUS on
> [  169.084195] PD RX, header: 0x363 [1]
> [  169.084200] state change SNK_NEGOTIATE_CAPABILITIES -> SNK_TRANSITION_SINK [rev2 POWER_NEGOTIATION]
> [  169.084206] Setting standby current 5000 mV @ 500 mA
> [  169.084209] Setting voltage/current limit 5000 mV 500 mA
> [  169.084220] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 500 ms [rev2 POWER_NEGOTIATION]
> [  169.260222] PD RX, header: 0x566 [1]
> [  169.260227] Setting voltage/current limit 9000 mV 2000 mA
> [  169.261315] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9000 ret:0
> [  169.261321] state change SNK_TRANSITION_SINK -> SNK_READY [rev2 POWER_NEGOTIATION]
> [  169.261570] AMS POWER_NEGOTIATION finished
> 
> Fixes: f0690a25a140b ("staging: typec: USB Type-C Port Manager (tcpm)")
> Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Changes since V2:
> * Refactored code based on Heikki's suggestion
> * Added reviewed-by tag from Guenter
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 17 +++++++++++++++++
>  include/linux/usb/pd.h        |  2 ++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 1c32bdf62852..aedc8bb9532a 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4131,6 +4131,23 @@ static void run_state_machine(struct tcpm_port *port)
>  		}
>  		break;
>  	case SNK_TRANSITION_SINK:
> +		/* From the USB PD spec:
> +		 * "The Sink Shall transition to Sink Standby before a positive or
> +		 * negative voltage transition of VBUS. During Sink Standby
> +		 * the Sink Shall reduce its power draw to pSnkStdby."
> +		 *
> +		 * This is not applicable to PPS though as the port can continue
> +		 * to draw negotiated power without switching to standby.
> +		 */
> +		if (port->supply_voltage != port->req_supply_voltage && !port->pps_data.active &&
> +		    port->current_limit * port->supply_voltage / 1000 > PD_P_SNK_STDBY_MW) {
> +			u32 stdby_ma = PD_P_SNK_STDBY_MW * 1000 / port->supply_voltage;
> +
> +			tcpm_log(port, "Setting standby current %u mV @ %u mA",
> +				 port->supply_voltage, stdby_ma);
> +			tcpm_set_current_limit(port, stdby_ma, port->supply_voltage);
> +		}
> +		fallthrough;
>  	case SNK_TRANSITION_SINK_VBUS:
>  		tcpm_set_state(port, hard_reset_state(port),
>  			       PD_T_PS_TRANSITION);
> diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
> index 70d681918d01..bf00259493e0 100644
> --- a/include/linux/usb/pd.h
> +++ b/include/linux/usb/pd.h
> @@ -493,4 +493,6 @@ static inline unsigned int rdo_max_power(u32 rdo)
>  #define PD_N_CAPS_COUNT		(PD_T_NO_RESPONSE / PD_T_SEND_SOURCE_CAP)
>  #define PD_N_HARD_RESET_COUNT	2
>  
> +#define PD_P_SNK_STDBY_MW	2500	/* 2500 mW */
> +
>  #endif /* __LINUX_USB_PD_H */
> -- 
> 2.31.1.295.g9ea45b61b8-goog

thanks,

-- 
heikki

Re: [PATCH v3 2/3] usb: typec: tcpm: Allow slow charging loops to comply to pSnkStby

[Heikki Krogerus]

On Tue, Apr 13, 2021 at 07:39:59PM -0700, Badhri Jagan Sridharan wrote:
> When a PD charger advertising Rp-3.0 is connected to a sink port, the
> sink port current limit would 3A, during SNK_DISCOVERY, till power
> negotiation starts. Once the negotiation starts the power limit needs
> to drop down to pSnkStby(500mA @ 5V) and to negotiated current limit
> once the explicit contract is in place. Not all charging loops can ramp
> up to 3A and drop down to 500mA within tSnkStdby which is 15ms. The port
> partner might hard reset if tSnkStdby is not met.
> 
> To solve this problem, this patch introduces slow-charger-loop which
> when set makes the port request PD_P_SNK_STDBY_MW upon entering
> SNK_DISCOVERY(instead of 3A or the 1.5A during SNK_DISCOVERY) and the
> actual currrent limit after RX of PD_CTRL_PSRDY for PD link or during
> SNK_READY for non-pd link.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Changes since V2:
> * Refactored code based on Heikki's suggestion
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index aedc8bb9532a..2ad5e14a6867 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -459,6 +459,12 @@ struct tcpm_port {
>  	/* Auto vbus discharge status */
>  	bool auto_vbus_discharge_enabled;
>  
> +	/*
> +	 * When set, port requests PD_P_SNK_STDBY_MW upon entering SNK_DISCOVERY and
> +	 * the actual currrent limit after RX of PD_CTRL_PSRDY for PD link,
> +	 * SNK_READY for non-pd link.
> +	 */
> +	bool slow_charger_loop;
>  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *dentry;
>  	struct mutex logbuffer_lock;	/* log buffer access lock */
> @@ -4047,9 +4053,11 @@ static void run_state_machine(struct tcpm_port *port)
>  		break;
>  	case SNK_DISCOVERY:
>  		if (port->vbus_present) {
> -			tcpm_set_current_limit(port,
> -					       tcpm_get_current_limit(port),
> -					       5000);
> +			u32 current_lim = tcpm_get_current_limit(port);
> +
> +			if (port->slow_charger_loop || (current_lim > PD_P_SNK_STDBY_MW / 5))
> +				current_lim = PD_P_SNK_STDBY_MW / 5;
> +			tcpm_set_current_limit(port, current_lim, 5000);
>  			tcpm_set_charge(port, true);
>  			tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
>  			break;
> @@ -4161,6 +4169,8 @@ static void run_state_machine(struct tcpm_port *port)
>  			port->pwr_opmode = TYPEC_PWR_MODE_PD;
>  		}
>  
> +		if (!port->pd_capable && port->slow_charger_loop)
> +			tcpm_set_current_limit(port, tcpm_get_current_limit(port), 5000);
>  		tcpm_swap_complete(port, 0);
>  		tcpm_typec_connect(port);
>  		mod_enable_frs_delayed_work(port, 0);
> @@ -5763,6 +5773,7 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
>  	port->typec_caps.type = ret;
>  	port->port_type = port->typec_caps.type;
>  
> +	port->slow_charger_loop = fwnode_property_read_bool(fwnode, "slow-charger-loop");
>  	if (port->port_type == TYPEC_PORT_SNK)
>  		goto sink;
>  
> -- 
> 2.31.1.295.g9ea45b61b8-goog

thanks,

-- 
heikki