Re: [PATCH 01/18] staging: typec: tcpm: Add get_usb2_current_limit tcpc_dev callback

From: Guenter Roeck
Date: Sun Aug 06 2017 - 10:52:43 EST

On 08/06/2017 07:29 AM, Hans de Goede wrote:

On 06-08-17 16:18, Guenter Roeck wrote:
On 08/06/2017 05:35 AM, Hans de Goede wrote:
A Rp signalling the default current limit indicates that we're possibly
connected to an USB2 power-source. In some cases the type-c
port-controller may provide the capability to detect the current-limit
for USB2 power-sources (through e.g. BC1.2 detection).

This commit adds an optional get_usb2_current_limit tcpc_dev callback
which allows the port-controller to return the detected current-limit
if the CC pin is pulled up with Rp.

Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
drivers/staging/typec/tcpm.c | 5 ++++-
drivers/staging/typec/tcpm.h | 1 +
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/typec/tcpm.c b/drivers/staging/typec/tcpm.c
index 20eb4ebcf8c3..9f5adace4309 100644
--- a/drivers/staging/typec/tcpm.c
+++ b/drivers/staging/typec/tcpm.c
@@ -660,7 +660,10 @@ static u32 tcpm_get_current_limit(struct tcpm_port *port)
- limit = 0;
+ if (port->tcpc->get_usb2_current_limit)

I think this callback should just be get_current_limit.

This is only used in the Rp-def case, which usually indicates being connected
with an A->C cable to a USB-2 device and the intend is for the callback to
implement some USB-2 specific method to detect the supported current-limit,
hence the name. If you prefer to name it just get_current_limit I can
change it for v2, but IMHO the usb2 part of the name is important as this
will not get called when USB-PD negotiation is used, nor when Rp has the Rp15
or Rp30 values.

As you say, it gets called in the Rp-def case, which can be set anytime.
I'd rather have a generic name and explain in tcpm.h as part of the API
description when it is used/called.

Note that it is also called in SNK_DISCOVERY if cc=Rp-def to calculate
and set the initial current limit, even with pd.




+ limit = port->tcpc->get_usb2_current_limit(port->tcpc);
+ else
+ limit = 0;
diff --git a/drivers/staging/typec/tcpm.h b/drivers/staging/typec/tcpm.h
index 19c307d31a5a..01b7d89379a3 100644
--- a/drivers/staging/typec/tcpm.h
+++ b/drivers/staging/typec/tcpm.h
@@ -108,6 +108,7 @@ struct tcpc_dev {
int (*init)(struct tcpc_dev *dev);
int (*get_vbus)(struct tcpc_dev *dev);
+ int (*get_usb2_current_limit)(struct tcpc_dev *dev); /* Optional */
int (*set_cc)(struct tcpc_dev *dev, enum typec_cc_status cc);
int (*get_cc)(struct tcpc_dev *dev, enum typec_cc_status *cc1,
enum typec_cc_status *cc2);