pd: support gotoMin and giveBack

In Sink mode, on the receipt of a GotoMin message,
reduce the current consumption to some minimum level.

BUG=chrome-os-partner:33688
TEST=Manual testing
	Used a Kevin, with test routine, to test GotoMin feature
	on another Kevin unit.

	Test routine:
		 if (!strcasecmp(argv[2], "gm")) {
		    ccprintf("send goto min\n");
		    send_control(port, PD_CTRL_GOTO_MIN);
		    send_control(port, PD_CTRL_PS_RDY);
		}

	Kevin with GotoMin feature:
		# ectool usbpdpower 0
		Port 0: SNK DRP PD 4277mV / 3000mA, max 5000mV / 3000mA / 15000mW
		Port 1: Disconnected

		After Test routine is executed:

		# ectool usbpdpower 0
		Port 0: SNK DRP PD 4906mV / 500mA, max 5000mV / 500mA / 2500mW
		Port 1: Disconnected
BRANCH=none

Change-Id: Iaac6e19706ceb10ccaff4d602d63fc086c808c8f
Reviewed-on: https://chromium-review.googlesource.com/425728
Commit-Ready: Sam Hurst <shurst@google.com>
Tested-by: Sam Hurst <shurst@google.com>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/usb_pd.h b/include/usb_pd.h
index 08eef75822..940424ecfa 100644
--- a/include/usb_pd.h
+++ b/include/usb_pd.h
@@ -904,6 +904,15 @@ int pd_is_max_request_allowed(void);
 void pd_process_source_cap(int port, int cnt, uint32_t *src_caps);
 
 /**
+ * Reduce the sink power consumption to a minimum value.
+ *
+ * @param port USB-C port number
+ * @param ma reduce current to minimum value.
+ * @param mv reduce voltage to minimum value.
+ */
+void pd_snk_give_back(int port, uint32_t * const ma, uint32_t * const mv);
+
+/**
  * Put a cap on the max voltage requested as a sink.
  * @param mv maximum voltage in millivolts.
  */