linux-kernel - [PATCH] usb: typec: tcpm: Fix SINK_DISCOVERY current limit for Rp-default

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Date:   Mon, 10 May 2021 14:17:56 -0700
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kyle Tso <kyletso@...gle.com>,
        Badhri Jagan Sridharan <badhri@...gle.com>
Subject: [PATCH] usb: typec: tcpm: Fix SINK_DISCOVERY current limit for Rp-default

This is a regression introduced by
<1373fefc6243cc96b3565f0ffffadfac4ccfb977>
"Allow slow charging loops to comply to pSnkStby".

When Source advertises Rp-default, tcpm would request 500mA when in
SINK_DISCOVERY, Type-C spec advises the sink to follow BC1.2 current
limits when Rp-default is advertised.
[12750.503381] Requesting mux state 1, usb-role 2, orientation 1
[12750.503837] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
[12751.003891] state change SNK_STARTUP -> SNK_DISCOVERY
[12751.003900] Setting voltage/current limit 5000 mV 500 mA

This patch restores the behavior where the tcpm would request 0mA when
Rp-default is advertised by the source.
[   73.174252] Requesting mux state 1, usb-role 2, orientation 1
[   73.174749] state change SNK_ATTACHED -> SNK_STARTUP [rev3 NONE_AMS]
[   73.674800] state change SNK_STARTUP -> SNK_DISCOVERY
[   73.674808] Setting voltage/current limit 5000 mV 0 mA

During SNK_DISCOVERY, Cap the current limit to PD_P_SNK_STDBY_MW / 5 only
for slow_charger_loop case.

Fixes: 1373fefc6243 ("Allow slow charging loops to comply to pSnkStby")
Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
---
 drivers/usb/typec/tcpm/tcpm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index c4fdc00a3bc8..a73299a08ef7 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -4055,7 +4055,7 @@ static void run_state_machine(struct tcpm_port *port)
 		if (port->vbus_present) {
 			u32 current_lim = tcpm_get_current_limit(port);

-			if (port->slow_charger_loop || (current_lim > PD_P_SNK_STDBY_MW / 5))
+			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);
-- 
2.31.1.607.g51e8a6a459-goog