pd: ignore cable reset

Identify and ignore cable reset PD command

BUG=chrome-os-partner:39464
BRANCH=samus
TEST=connect two samus'. on one samus add code to send a cable
reset like such:

int send_cable_reset(int port)
{
	int off;

	CPRINTF("C%d Send cable reset\n", port);

	/* 64-bit preamble */
	off = pd_write_preamble(port);
	/* Hard-Reset: 3x RST-1 + 1x RST-2 */
	off = pd_write_sym(port, off, BMC(PD_RST1));
	off = pd_write_sym(port, off, BMC(PD_SYNC1));
	off = pd_write_sym(port, off, BMC(PD_RST1));
	off = pd_write_sym(port, off, BMC(PD_SYNC3));
	/* Ensure that we have a final edge */
	off = pd_write_last_edge(port, off);
	/* Transmit the packet */
	if (pd_start_tx(port, pd[port].polarity, off) < 0) {
		pd[port].send_error = -5;
		return -5;
	}
	pd_tx_done(port, pd[port].polarity);
	/* Keep RX monitoring on */
	pd_rx_enable_monitoring(port);
	return 0;
}

Without this CL, the receiving samus times out and ends
up causing equivalent of hard reset. With this CL, we receive
cable reset and drop it.

Also used twinkie to measure goodCRC delay. No measureable
change in delay on samus and zinger. Samus delay is ~70us and
zinger delay is ~65us.

Change-Id: Ic0e871c8cf96502b861f430e05ee145881fb55fa
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/266981
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/chip/stm32/usb_pd_phy.c b/chip/stm32/usb_pd_phy.c
index 1db963c588..6c53281346 100644
--- a/chip/stm32/usb_pd_phy.c
+++ b/chip/stm32/usb_pd_phy.c
@@ -180,7 +180,9 @@ int pd_find_preamble(int port)
 		if (all == 0x36db6db6)
 			return bit - 1; /* should be SYNC-1 */
 		if (all == 0xF33F3F3F)
-			return -2; /* got HARD-RESET */
+			return PD_ERR_HARD_RESET; /* got HARD-RESET */
+		if (all == 0x3c7fe0ff)
+			return PD_ERR_CABLE_RESET; /* got CABLE-RESET */
 	}
 	return -1;
 }