TCPMv2: Allow reduced functionality to PD2.0 features

Some TCPCs only work with PD2.0 messages. So a config flag
is added to restrict the TCPMv2 stack to working at PD2.0
revision.

If the config flag is defined, the PD revision is fixed at
PD2.0. In a future CL, the config flag can also be used
to reduce code size by not compiling in PD3.0 features.

BUG=chromium:1021235
BRANCH=none
TEST=make -j buildall
	Manual tests:
	Verified that the stack only works at PD2.0 rev,
	using a twinki and several docks.
Signed-off-by: Sam Hurst <shurst@google.com>

Change-Id: Ic5fc8d24baec3bdecffb4dd54a6aac28d72550cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2032145
Tested-by: Sam Hurst <shurst@google.com>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Commit-Queue: Sam Hurst <shurst@google.com>

4 files changed, 28 insertions, 11 deletions

diff --git a/common/usbc/usb_pe_drp_sm.c b/common/usbc/usb_pe_drp_sm.c
index 2f627f367f..c490508674 100644
--- a/common/usbc/usb_pe_drp_sm.c
+++ b/common/usbc/usb_pe_drp_sm.c
@@ -1335,8 +1335,7 @@ static void pe_src_send_capabilities_run(int port)
 			 * ports.
 			 */
 			prl_set_rev(port, TCPC_TX_SOP,
-				(PD_HEADER_REV(emsg[port].header) > PD_REV30) ?
-				PD_REV30 : PD_HEADER_REV(emsg[port].header));
+			MIN(PD_REVISION, PD_HEADER_REV(emsg[port].header)));
 
 			/*
 			 * If port partner runs PD 2.0, cable communication must
@@ -2034,7 +2033,6 @@ static void pe_snk_wait_for_capabilities_run(int port)
 static void pe_snk_evaluate_capability_entry(int port)
 {
 	uint32_t *pdo = (uint32_t *)emsg[port].buf;
-	uint32_t header = emsg[port].header;
 	uint32_t num = emsg[port].len >> 2;
 	int i;
 
@@ -2044,8 +2042,8 @@ static void pe_snk_evaluate_capability_entry(int port)
 	pe[port].hard_reset_counter = 0;
 
 	/* Set to highest revision supported by both ports. */
-	prl_set_rev(port, TCPC_TX_SOP, (PD_HEADER_REV(header) > PD_REV30) ?
-					PD_REV30 : PD_HEADER_REV(header));
+	prl_set_rev(port, TCPC_TX_SOP,
+			MIN(PD_REVISION, PD_HEADER_REV(emsg[port].header)));
 
 	/*
 	 * If port partner runs PD 2.0, cable communication must
diff --git a/common/usbc/usb_prl_sm.c b/common/usbc/usb_prl_sm.c
index 9314049bf8..1cc5636118 100644
--- a/common/usbc/usb_prl_sm.c
+++ b/common/usbc/usb_prl_sm.c
@@ -322,11 +322,11 @@ static void prl_init(int port)
 	 * partner doesn't support this revision, the Protocol Engine will
 	 * lower this value to the revision supported by the partner.
 	 */
-	pdmsg[port].rev[TCPC_TX_SOP] = PD_REV30;
-	pdmsg[port].rev[TCPC_TX_SOP_PRIME] = PD_REV30;
-	pdmsg[port].rev[TCPC_TX_SOP_PRIME_PRIME] = PD_REV30;
-	pdmsg[port].rev[TCPC_TX_SOP_DEBUG_PRIME] = PD_REV30;
-	pdmsg[port].rev[TCPC_TX_SOP_DEBUG_PRIME_PRIME] = PD_REV30;
+	pdmsg[port].rev[TCPC_TX_SOP] = PD_REVISION;
+	pdmsg[port].rev[TCPC_TX_SOP_PRIME] = PD_REVISION;
+	pdmsg[port].rev[TCPC_TX_SOP_PRIME_PRIME] = PD_REVISION;
+	pdmsg[port].rev[TCPC_TX_SOP_DEBUG_PRIME] = PD_REVISION;
+	pdmsg[port].rev[TCPC_TX_SOP_DEBUG_PRIME_PRIME] = PD_REVISION;
 	pdmsg[port].flags = 0;
 
 	prl_hr[port].flags = 0;
diff --git a/include/config.h b/include/config.h
index ba48d21b71..89b622cd85 100644
--- a/include/config.h
+++ b/include/config.h
@@ -3746,7 +3746,20 @@
 /* Define if this board, operating as a sink, can give power back to a source */
 #undef CONFIG_USB_PD_GIVE_BACK
 
-/* Enable USB PD Rev3.0 features */
+/*
+ * Enable USB PD Rev2.0 features only
+ * NOTE:
+ *   This flag is only used with TCPMv2. The TCPMv2 stack defaults to PD3.0
+ *   and this flag disabled PD3.0 features.
+ */
+#undef CONFIG_USB_PD_REV20
+
+/*
+ * Enable USB PD Rev3.0 features
+ * NOTE:
+ *    This flag is only used with TCPMv1. The TCPMv1 stack defaults to PD2.0
+ *    and this flag enabled PD3.0 features.
+ */
 #undef CONFIG_USB_PD_REV30
 
 /* Major and Minor ChromeOS specific PD device Hardware IDs. */
diff --git a/include/usb_pd.h b/include/usb_pd.h
index 8f313b8c64..cdd111d687 100644
--- a/include/usb_pd.h
+++ b/include/usb_pd.h
@@ -546,6 +546,12 @@ enum pd_rev_type {
 	PD_REV30,
 };
 
+#ifdef CONFIG_USB_PD_REV20
+#define PD_REVISION     PD_REV20
+#else
+#define PD_REVISION     PD_REV30
+#endif
+
 /* Cable structure for storing cable attributes */
 struct pd_cable {
 	/* Note: the following fields are used by TCPMv1 */