USB4: Allow entering USB4 mode for devices and cables without SVID

USB4 devices and Passive cables with USB4 speed that do not support
Intel SVID should enter USB4 mode with cable speed to TBT Gen2 passive
cable or board's max TBT speed, whichever is lower.
Ref:USB Type-C cable and connector specification 2.0
Figure 5-1 USB4 Discovery and Entry Flow model

BUG=b:154308721
BRANCH=None
TEST=Able to enter USB4 mode with Passive Gen2 cables

Signed-off-by: Ayushee <ayushee.shah@intel.com>
Change-Id: Ib6e4463f2ed0682cee14a84e5d1d9560e286bd37
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2159938
Reviewed-by: Keith Short <keithshort@chromium.org>
Tested-by: Ayushee Shah <ayushee.shah@intel.corp-partner.google.com>

1 files changed, 68 insertions, 44 deletions

diff --git a/common/usb_pd_policy.c b/common/usb_pd_policy.c
index 9fd322f73d..75ebcbd869 100644
--- a/common/usb_pd_policy.c
+++ b/common/usb_pd_policy.c
@@ -467,6 +467,8 @@ static inline void disable_usb4_mode(int port)
 static bool is_cable_ready_to_enter_usb4(int port, int cnt)
 {
 	/* TODO: USB4 enter mode for Active cables */
+
+	/* TODO: Check for port's maximum supported Thunderbolt speed */
 	if (IS_ENABLED(CONFIG_USB_PD_USB4) &&
 	   (get_usb_pd_cable_type(port) == IDH_PTYPE_PCABLE) &&
 	    is_vdo_present(cnt, VDO_INDEX_PTYPE_CABLE1)) {
@@ -635,10 +637,72 @@ __overridable bool board_is_tbt_usb4_port(int port)
 	return true;
 }
 
+static void usb_pd_limit_cable_speed(int port)
+{
+	enum tbt_compat_cable_speed max_tbt_speed =
+				board_get_max_tbt_speed(port);
+
+	/* Cable does not have Intel SVID for Discover SVID */
+	if (is_limit_tbt_cable_speed(port))
+		cable[port].cable_mode_resp.tbt_cable_speed =
+				TBT_SS_U32_GEN1_GEN2;
+
+	if (cable[port].cable_mode_resp.tbt_cable_speed > max_tbt_speed)
+		cable[port].cable_mode_resp.tbt_cable_speed = max_tbt_speed;
+}
+
+static int process_am_discover_svids(int port, int cnt, uint32_t *payload)
+{
+	int prev_svid_cnt = discovery[port].svid_cnt;
+
+	dfp_consume_svids(port, cnt, payload);
+
+	/*
+	 * Ref: USB Type-C Cable and Connector Specification,
+	 * figure F-1: TBT3 Discovery Flow
+	 *
+	 * For USB4 mode if device or cable doesn't have Intel SVID,
+	 * disable Thunderbolt-Compatible mode directly enter USB4 mode.
+	 *
+	 * For Thunderbolt-compatible, check if 0x8087 is received for
+	 * Discover SVID SOP. If not, disable Thunderbolt-compatible mode
+	 *
+	 * If 0x8087 is not received for Discover SVID SOP' limit to TBT
+	 * passive Gen 2 cable.
+	 */
+	if (is_tbt_compat_enabled(port)) {
+		bool intel_svid = is_intel_svid(port, prev_svid_cnt);
+
+		if (!intel_svid) {
+			if (is_usb4_mode_enabled(port)) {
+				disable_tbt_compat_mode(port);
+				limit_tbt_cable_speed(port);
+				usb_pd_limit_cable_speed(port);
+				enable_enter_usb4_mode(port);
+				usb_mux_set_safe_mode(port);
+				if (is_transmit_msg_sop_prime(port))
+					disable_transmit_sop_prime(port);
+				return 0;
+			}
+
+			if (is_transmit_msg_sop_prime(port))
+				limit_tbt_cable_speed(port);
+			else
+				disable_tbt_compat_mode(port);
+		} else {
+			enable_transmit_sop_prime(port);
+			return dfp_discover_svids(payload);
+		}
+	}
+
+	disable_transmit_sop_prime(port);
+
+	return dfp_discover_modes(port, payload);
+}
+
 static int process_tbt_compat_discover_modes(int port, uint32_t *payload)
 {
 	int rsize;
-	enum tbt_compat_cable_speed max_tbt_speed;
 
 	/*
 	 * For active cables, Enter mode: SOP', SOP'', SOP
@@ -649,17 +713,8 @@ static int process_tbt_compat_discover_modes(int port, uint32_t *payload)
 		/* Store Discover Mode SOP' response */
 		cable[port].cable_mode_resp.raw_value = payload[1];
 
-		/* Cable does not have Intel SVID for Discover SVID */
-		if (is_limit_tbt_cable_speed(port))
-			cable[port].cable_mode_resp.tbt_cable_speed =
-						TBT_SS_U32_GEN1_GEN2;
-
-		max_tbt_speed = board_get_max_tbt_speed(port);
-		if (cable[port].cable_mode_resp.tbt_cable_speed >
-			max_tbt_speed) {
-			cable[port].cable_mode_resp.tbt_cable_speed =
-				max_tbt_speed;
-		}
+		/* Limits cable speed if applicable */
+		usb_pd_limit_cable_speed(port);
 
 		/*
 		 * Enter Mode SOP' (Cable Enter Mode) and Enter USB SOP' is
@@ -899,38 +954,7 @@ int pd_svdm(int port, int cnt, uint32_t *payload, uint32_t **rpayload,
 #endif
 			break;
 		case CMD_DISCOVER_SVID:
-			{
-			int prev_svid_cnt = discovery[port].svid_cnt;
-			dfp_consume_svids(port, cnt, payload);
-			/*
-			 * Ref: USB Type-C Cable and Connector Specification,
-			 * figure F-1: TBT3 Discovery Flow
-			 *
-			 * Check if 0x8087 is received for Discover SVID SOP.
-			 * If not, disable Thunderbolt-compatible mode
-			 *
-			 * If 0x8087 is not received for Discover SVID SOP'
-			 * limit to TBT passive Gen 2 cable
-			 */
-			if (is_tbt_compat_enabled(port)) {
-				bool intel_svid =
-					is_intel_svid(port, prev_svid_cnt);
-				if (is_transmit_msg_sop_prime(port)) {
-					if (!intel_svid)
-						limit_tbt_cable_speed(port);
-				} else if (intel_svid) {
-					rsize = dfp_discover_svids(payload);
-					enable_transmit_sop_prime(port);
-					break;
-				} else {
-					disable_tbt_compat_mode(port);
-				}
-			}
-
-			rsize = dfp_discover_modes(port, payload);
-
-			disable_transmit_sop_prime(port);
-			}
+			rsize = process_am_discover_svids(port, cnt, payload);
 			break;
 		case CMD_DISCOVER_MODES:
 			dfp_consume_modes(port, cnt, payload);