USB-PD: Make sink automatically enter EPR mode

Currently, EPR mode is entered only by 'pd' console command.
This CL makes sink ports enter EPR mode automatically.

PE_FLAGS_EPR_EXPLICIT_EXIT is cleared when soft reset is sent, a source
is disconnected, or EPR is entered again.

BUG=b:257320026,b:274929940
BRANCH=None
TEST=On Agah, plug AC, observe automatic entry to EPR. Then type 'pd 1
epr exit' and observe EPR mode is not re-entered. Then replug AC and
observe the port enters EPR automatically.
TEST=make run-usb_pd_console

Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Change-Id: Ie2b94323ba404d44ee70756e1893c065c34911fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4421425
Reviewed-by: Eric Yilun Lin <yllin@google.com>

5 files changed, 37 insertions, 3 deletions

diff --git a/common/usbc/usb_pd_console.c b/common/usbc/usb_pd_console.c
index d1c82bafda..ae6527b601 100644
--- a/common/usbc/usb_pd_console.c
+++ b/common/usbc/usb_pd_console.c
@@ -226,6 +226,8 @@ static
 			req = DPM_REQUEST_EPR_MODE_ENTRY;
 		} else if (!strcasecmp(argv[3], "exit")) {
 			req = DPM_REQUEST_EPR_MODE_EXIT;
+			/* Prevent snk_ready from repeatedly entering EPR. */
+			pe_snk_epr_explicit_exit(port);
 		} else {
 			return EC_ERROR_PARAM3;
 		}
diff --git a/common/usbc/usb_pe_drp_sm.c b/common/usbc/usb_pe_drp_sm.c
index 767fed302b..dba06dfbfb 100644
--- a/common/usbc/usb_pe_drp_sm.c
+++ b/common/usbc/usb_pe_drp_sm.c
@@ -1159,6 +1159,11 @@ bool pe_snk_in_epr_mode(int port)
 	return PE_CHK_FLAG(port, PE_FLAGS_IN_EPR);
 }
 
+void pe_snk_epr_explicit_exit(int port)
+{
+	PE_SET_FLAG(port, PE_FLAGS_EPR_EXPLICIT_EXIT);
+}
+
 bool pe_snk_can_enter_epr_mode(int port)
 {
 	/*
@@ -3749,9 +3754,12 @@ static void pe_snk_ready_entry(int port)
 	 */
 	pe_update_wait_and_add_jitter_timer(port);
 
-	if (IS_ENABLED(CONFIG_USB_PD_EPR) && pe_snk_in_epr_mode(port)) {
-		pd_timer_enable(port, PE_TIMER_SINK_EPR_KEEP_ALIVE,
-				PD_T_SINK_EPR_KEEP_ALIVE);
+	if (IS_ENABLED(CONFIG_USB_PD_EPR)) {
+		if (pe_snk_in_epr_mode(port))
+			pd_timer_enable(port, PE_TIMER_SINK_EPR_KEEP_ALIVE,
+					PD_T_SINK_EPR_KEEP_ALIVE);
+		else if (!PE_CHK_FLAG(port, PE_FLAGS_EPR_EXPLICIT_EXIT))
+			pd_dpm_request(port, DPM_REQUEST_EPR_MODE_ENTRY);
 	}
 }
 
@@ -4138,6 +4146,7 @@ static void pe_send_soft_reset_entry(int port)
 	print_current_state(port);
 
 	PE_CLR_FLAG(port, PE_FLAGS_ENTERING_EPR);
+	PE_CLR_FLAG(port, PE_FLAGS_EPR_EXPLICIT_EXIT);
 
 	/* Reset Protocol Layer (softly) */
 	prl_reset_soft(port);
@@ -7913,6 +7922,7 @@ static void pe_ddr_perform_data_reset_exit(int port)
 static void pe_enter_epr_mode(int port)
 {
 	PE_CLR_FLAG(port, PE_FLAGS_ENTERING_EPR);
+	PE_CLR_FLAG(port, PE_FLAGS_EPR_EXPLICIT_EXIT);
 	PE_SET_FLAG(port, PE_FLAGS_IN_EPR);
 	CPRINTS("C%d: Entered EPR", port);
 }
diff --git a/common/usbc/usb_pe_private.h b/common/usbc/usb_pe_private.h
index 5eafb7befd..b71cfced86 100644
--- a/common/usbc/usb_pe_private.h
+++ b/common/usbc/usb_pe_private.h
@@ -92,6 +92,11 @@ enum {
 	PE_FLAGS_ENTERING_EPR_FN,
 	/* In EPR mode */
 	PE_FLAGS_IN_EPR_FN,
+	/*
+	 * Indicate the port exited EPR mode explicitly. If this is set, the
+	 * port wouldn't enter EPR mode automatically.
+	 */
+	PE_FLAGS_EPR_EXPLICIT_EXIT_FN,
 	/* Discovery disabled due to UFP/PD 2.0 constraint. */
 	PE_FLAGS_DISCOVERY_DISABLED_FN,
 	/* Last element */
diff --git a/include/usb_pe_sm.h b/include/usb_pe_sm.h
index 9672c6b26b..21cc65d43d 100644
--- a/include/usb_pe_sm.h
+++ b/include/usb_pe_sm.h
@@ -210,6 +210,13 @@ void pe_clear_port_data(int port);
 bool pe_snk_in_epr_mode(int port);
 
 /**
+ * Make a sink exit EPR mode explicitly.
+ *
+ * @param port USB-C port number
+ */
+void pe_snk_epr_explicit_exit(int port);
+
+/**
  * Checks whether the port is ready for EPR entry.
  *
  * @param port USB-C port number
diff --git a/test/usb_pd_console.c b/test/usb_pd_console.c
index a835a643f8..119fe7131d 100644
--- a/test/usb_pd_console.c
+++ b/test/usb_pd_console.c
@@ -35,6 +35,7 @@ static bool pe_get_current_state_called;
 static bool pe_get_flags_called;
 static bool pe_is_explicit_contract_called;
 static bool pe_snk_in_epr_mode_called;
+static bool pe_snk_epr_explicit_exit_called;
 static bool pd_get_dual_role_called;
 static bool board_get_usb_pd_port_count_called;
 static bool pd_srccaps_dump_called;
@@ -86,6 +87,11 @@ bool pe_snk_in_epr_mode(int port)
 	return true;
 }
 
+void pe_snk_epr_explicit_exit(int port)
+{
+	pe_snk_epr_explicit_exit_called = true;
+}
+
 const char *pe_get_current_state(int port)
 {
 	pe_get_current_state_called = true;
@@ -726,18 +732,22 @@ static int test_command_pd_epr(void)
 	request = 0;
 	pd_get_power_role_called = false;
 	pd_get_power_role_return = PD_ROLE_SINK;
+	pe_snk_epr_explicit_exit_called = false;
 	TEST_ASSERT(command_pd(argc, argv) == EC_SUCCESS);
 	TEST_ASSERT(pd_get_power_role_called);
 	TEST_ASSERT(request == DPM_REQUEST_EPR_MODE_ENTRY);
+	TEST_ASSERT(!pe_snk_epr_explicit_exit_called);
 
 	/* Return SUCCESS with request==DPM_REQUEST_EPR_MODE_EXIT. */
 	argv[3] = "exit";
 	request = 0;
 	pd_get_power_role_called = false;
 	pd_get_power_role_return = PD_ROLE_SINK;
+	pe_snk_epr_explicit_exit_called = false;
 	TEST_ASSERT(command_pd(argc, argv) == EC_SUCCESS);
 	TEST_ASSERT(pd_get_power_role_called);
 	TEST_ASSERT(request == DPM_REQUEST_EPR_MODE_EXIT);
+	TEST_ASSERT(pe_snk_epr_explicit_exit_called);
 
 	/* Return EC_ERROR_PARAM3 for invalid sub-command. */
 	argv[3] = "start";