twinkie: add simple text tracing mechanism

When using the Twinkie dongle without a protocol decoder on the host,
add a simple text tracing mechanism, so the user can get the timestamped traces
of the packets on the wire (in a best effort fashion).

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BRANCH=none
BUG=none
TEST=On Twinkie command-line, type "tw trace on"
then plug a DingDong to Samus through Twinkie and
see the PD message traces on the console.

Change-Id: I4fa35d6783cc6279c95209c86f37e6d717de7301
Reviewed-on: https://chromium-review.googlesource.com/237222
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Trybot-Ready: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/usb_pd.h b/include/usb_pd.h
index e79e2d907c..0f226096b8 100644
--- a/include/usb_pd.h
+++ b/include/usb_pd.h
@@ -1324,7 +1324,27 @@ void pd_hw_release(int port);
  */
 void pd_hw_init(int port, int role);
 
+/**
+ * Initialize the reception side of hardware used for PD.
+ *
+ * This is a subset of pd_hw_init() including only :
+ * the comparators + the RX edge delay timer + the RX DMA.
+ *
+ * @param port USB-C port number
+ */
+void pd_hw_init_rx(int port);
+
 /* --- Protocol layer functions --- */
+
+/**
+ * Decode a raw packet in the RX buffer.
+ *
+ * @param port USB-C port number
+ * @param payload buffer to store the packet payload (must be 7x 32-bit)
+ * @return the packet header or <0 in case of error
+ */
+int pd_analyze_rx(int port, uint32_t *payload);
+
 /**
  * Get connected state
  *