usb_pd: TBT: Refactor limiting the cable speed

Refactored 'get_tbt_cable_speed()' to return thunderbolt-compatible speed
as per the speed supported by DUT's port or cable speed whichever is
lowest.

Also removed 'usb_pd_limit_cable_speed()' to retain cables's actual VDO
response.

BUG=b:157671582
BRANCH=none
TEST=Able to limit thunderbolt cable speed, if the cable speed is higher
     than the speed supported by DUT's port.

Signed-off-by: Ayushee <ayushee.shah@intel.com>
Change-Id: I77d3efddb425daa7bd12e9ed21be7088074285bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2227088
Reviewed-by: Vijay P Hiremath <vijay.p.hiremath@intel.com>
Reviewed-by: Keith Short <keithshort@chromium.org>

5 files changed, 28 insertions, 45 deletions

diff --git a/common/usb_pd_alt_mode_dfp.c b/common/usb_pd_alt_mode_dfp.c
index 79ac93d94e..051fa9740c 100644
--- a/common/usb_pd_alt_mode_dfp.c
+++ b/common/usb_pd_alt_mode_dfp.c
@@ -793,12 +793,23 @@ bool is_tbt_compat_mode(int port, int cnt, const uint32_t *payload)
 		PD_VDO_RESP_MODE_INTEL_TBT(payload[VDO_INDEX_IDH]);
 }
 
-bool cable_supports_tbt_speed(int port)
+enum tbt_compat_cable_speed get_tbt_cable_speed(int port)
 {
 	struct pd_cable *cable = pd_get_cable_attributes(port);
+	enum tbt_compat_cable_speed max_tbt_speed =
+				board_get_max_tbt_speed(port);
+
+	return cable->cable_mode_resp.tbt_cable_speed > max_tbt_speed ?
+		max_tbt_speed : cable->cable_mode_resp.tbt_cable_speed;
+}
+
+bool cable_supports_tbt_speed(int port)
+{
+	enum tbt_compat_cable_speed tbt_cable_speed =
+				get_tbt_cable_speed(port);
 
-	return (cable->cable_mode_resp.tbt_cable_speed == TBT_SS_TBT_GEN3 ||
-		cable->cable_mode_resp.tbt_cable_speed == TBT_SS_U32_GEN1_GEN2);
+	return (tbt_cable_speed == TBT_SS_TBT_GEN3 ||
+		tbt_cable_speed == TBT_SS_U32_GEN1_GEN2);
 }
 
 /*
diff --git a/common/usb_pd_policy.c b/common/usb_pd_policy.c
index e5df19db5d..38bb04f83b 100644
--- a/common/usb_pd_policy.c
+++ b/common/usb_pd_policy.c
@@ -211,12 +211,6 @@ union tbt_mode_resp_device get_dev_tbt_vdo(int port)
 	return cable[port].dev_mode_resp;
 }
 
-enum tbt_compat_cable_speed get_tbt_cable_speed(int port)
-{
-	/* tbt_cable_speed is zero when uninitialized */
-	return cable[port].cable_mode_resp.tbt_cable_speed;
-}
-
 enum tbt_compat_rounded_support get_tbt_rounded_support(int port)
 {
 	/* tbt_rounded_support is zero when uninitialized */
@@ -517,20 +511,6 @@ static enum tcpm_transmit_type get_tcpm_transmit_msg_type(int port)
 	return TCPC_TX_SOP;
 }
 
-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;
@@ -547,7 +527,8 @@ static int process_am_discover_svids(int port, int cnt, uint32_t *payload)
 	 * 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.
+	 * disable Thunderbolt-Compatible mode directly enter USB4 mode
+	 * with USB3.2 Gen1/Gen2 speed.
 	 *
 	 * For Thunderbolt-compatible, check if 0x8087 is received for
 	 * Discover SVID SOP. If not, disable Thunderbolt-compatible mode
@@ -561,8 +542,8 @@ static int process_am_discover_svids(int port, int cnt, uint32_t *payload)
 		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);
+				cable[port].cable_mode_resp.tbt_cable_speed =
+					TBT_SS_U32_GEN1_GEN2;
 				enable_enter_usb4_mode(port);
 				usb_mux_set_safe_mode(port);
 				if (is_transmit_msg_sop_prime(port))
@@ -599,9 +580,6 @@ static int process_tbt_compat_discover_modes(int port,
 		/* Store Discover Mode SOP' response */
 		cable[port].cable_mode_resp.raw_value = payload[1];
 
-		/* Limits cable speed if applicable */
-		usb_pd_limit_cable_speed(port);
-
 		/*
 		 * Enter Mode SOP' (Cable Enter Mode) and Enter USB SOP' is
 		 * skipped for passive cables.
diff --git a/common/usbc/usb_sm.c b/common/usbc/usb_sm.c
index 800181f7b2..fbc227ded5 100644
--- a/common/usbc/usb_sm.c
+++ b/common/usbc/usb_sm.c
@@ -211,13 +211,6 @@ union tbt_mode_resp_device get_dev_tbt_vdo(int port)
 	return dev_resp;
 }
 
-enum tbt_compat_cable_speed get_tbt_cable_speed(int port)
-{
-	enum tbt_compat_cable_speed cable_speed = 0;
-
-	return cable_speed;
-}
-
 enum tbt_compat_rounded_support get_tbt_rounded_support(int port)
 {
 	enum tbt_compat_rounded_support tbt_round = 0;
diff --git a/driver/retimer/bb_retimer.c b/driver/retimer/bb_retimer.c
index 518aebd101..ea287a927b 100644
--- a/driver/retimer/bb_retimer.c
+++ b/driver/retimer/bb_retimer.c
@@ -226,7 +226,7 @@ static void retimer_set_state_dfp(int port, mux_state_t mux_state,
 		 * 10..11b - Reserved
 		 */
 		*set_retimer_con |= BB_RETIMER_USB4_TBT_CABLE_SPEED_SUPPORT(
-						cable_resp.tbt_cable_speed);
+						get_tbt_cable_speed(port));
 		/*
 		 * Bits 29-28: TBT_GEN_SUPPORT
 		 * 00b - 3rd generation TBT (10.3125 and 20.625Gb/s)
diff --git a/include/usb_pd.h b/include/usb_pd.h
index cdeaafacbe..a81a6184b3 100644
--- a/include/usb_pd.h
+++ b/include/usb_pd.h
@@ -2038,14 +2038,6 @@ union tbt_mode_resp_cable get_cable_tbt_vdo(int port);
 union tbt_mode_resp_device get_dev_tbt_vdo(int port);
 
 /**
- * Update Mux on entering Thunderbolt-compatible mode
- *
- * @param port USB-C port number
- * @return cable speed
- */
-enum tbt_compat_cable_speed get_tbt_cable_speed(int port);
-
-/**
  * Return Thunderbolt rounded support
  * Rounded support indicates if the cable can support rounding the
  * frequency depending upon the cable generation.
@@ -2100,6 +2092,15 @@ bool is_intel_svid(int port, int prev_svid_cnt);
  */
 bool is_tbt_compat_mode(int port, int cnt, const uint32_t *payload);
 
+/**
+ * Returns Thunderbolt-compatible cable speed according to the port if,
+ * port supports lesser speed than the cable
+ *
+ * @param port USB-C port number
+ * @return thunderbolt-cable cable speed
+ */
+enum tbt_compat_cable_speed get_tbt_cable_speed(int port);
+
 /*
  * Checks if the cable supports Thunderbolt speed.
  *